Index: src/chat/chat.c
===================================================================
--- src/chat/chat.c	(revision 0)
+++ src/chat/chat.c	(revision 0)
@@ -0,0 +1,789 @@
+/*
+     This file is part of GNUnet.
+     (C) 2008, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file chat/chat_api.c
+ * @brief convenience API for sending and receiving chat messages
+ * @author Christian Grothoff
+ * @author Nathan Evans
+ * @author Vitaly Minko
+ */
+
+#include "platform.h"
+#include "gnunet_constants.h"
+#include "gnunet_protocols.h"
+#include "gnunet_signatures.h"
+#include "chat.h"
+
+#define DEBUG_CHAT GNUNET_YES
+#define NICK_IDENTITY_PREFIX ".chat_identity_"
+
+
+/**
+ * Handle for a (joined) chat room.
+ */
+struct GNUNET_CHAT_Room
+{
+  struct GNUNET_CLIENT_Connection *client;
+
+  const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+  struct GNUNET_CONTAINER_MetaData *member_info;
+
+  char *room_name;
+
+  struct GNUNET_CRYPTO_RsaPrivateKey *my_private_key;
+
+  struct MemberList *members;
+
+  GNUNET_CHAT_MessageCallback message_callback;
+
+  void *message_callback_cls;
+
+  GNUNET_CHAT_MemberListCallback member_list_callback;
+
+  void *member_list_callback_cls;
+
+  GNUNET_CHAT_MessageConfirmation confirmation_callback;
+
+  void *confirmation_cls;
+
+  uint32_t sequence_number;
+
+  uint32_t msg_options;
+
+};
+
+/**
+ * Linked list of members in the chat room.
+ */
+struct MemberList
+{
+  struct MemberList *next;
+
+  /**
+   * Description of the member.
+   */
+  struct GNUNET_CONTAINER_MetaData *meta;
+
+  /**
+   * Member ID (pseudonym).
+   */
+  GNUNET_HashCode id;
+
+};
+
+/**
+ * Context for transmitting a send-message request.
+ */
+struct GNUNET_CHAT_SendMessageContext
+{
+  /**
+   * Handle for the chat room.
+   */
+  struct GNUNET_CHAT_Room *chat_room;
+
+  /**
+   * Message that we're sending.
+   */
+  char *message;
+
+  /**
+   * Options for the message.
+   */
+  enum GNUNET_CHAT_MsgOptions options;
+
+  /**
+   * Receiver of the message. NULL to send to everyone in the room.
+   */
+  const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *receiver;
+
+  /**
+   * Sequence id of the message.
+   */
+  uint32_t sequence_number;
+
+};
+
+/**
+ * Context for transmitting a confirmation receipt.
+ */
+struct GNUNET_CHAT_SendReceiptContext
+{
+  /**
+   * Handle for the chat room.
+   */
+  struct GNUNET_CHAT_Room *chat_room;
+
+  /**
+   * The original message that we're going to acknowledge.
+   */
+  struct ReceiveNotificationMessage *received_msg;
+
+};
+
+/**
+ * Ask client to send a join request.
+ */
+static int
+GNUNET_CHAT_rejoin_room (struct GNUNET_CHAT_Room *chat_room);
+
+
+/**
+ * Transmit a confirmation receipt to the chat service.
+ *
+ * @param cls closure, pointer to the 'struct GNUNET_CHAT_SendReceiptContext'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_acknowledge_request (void *cls,
+			      size_t size, 
+			      void *buf)
+{
+  struct GNUNET_CHAT_SendReceiptContext *src = cls;
+  struct ConfirmationReceiptMessage *receipt;
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded pub_key;
+  uint16_t msg_len;
+  size_t msg_size;
+
+  if (NULL == buf)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Could not transmit confirmation receipt\n"));
+      return 0;
+    }
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting confirmation receipt to the service\n");
+#endif
+  msg_size = sizeof (struct ConfirmationReceiptMessage);
+  GNUNET_assert (size >= msg_size);
+  receipt = buf;
+  receipt->header.size = htons (msg_size);
+  receipt->header.type =
+    htons (GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_RECEIPT);
+  receipt->sequence_number = src->received_msg->sequence_number;
+  receipt->reserved2 = 0;
+  receipt->timestamp = GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get ());
+  GNUNET_CRYPTO_rsa_key_get_public (src->chat_room->my_private_key, &pub_key);
+  GNUNET_CRYPTO_hash (&pub_key,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      &receipt->target);
+  receipt->author = src->received_msg->sender;
+  receipt->purpose.purpose =
+    htonl (GNUNET_SIGNATURE_PURPOSE_CHAT_RECEIPT);
+  receipt->purpose.size =
+    htonl (msg_size -
+	   sizeof (struct GNUNET_MessageHeader) -
+	   sizeof (uint32_t) -
+	   sizeof (struct GNUNET_CRYPTO_RsaSignature));
+  msg_len = ntohs (src->received_msg->header.size) -
+    sizeof (struct ReceiveNotificationMessage);
+  GNUNET_CRYPTO_hash (&src->received_msg[1], msg_len, &receipt->content);
+  GNUNET_assert (GNUNET_OK == 
+		 GNUNET_CRYPTO_rsa_sign (src->chat_room->my_private_key,
+					 &receipt->purpose,
+					 &receipt->signature));
+  GNUNET_free (src->received_msg);
+  GNUNET_free (src);
+  return msg_size;
+}
+
+
+/**
+ * Handles messages received from the service.  Calls the proper client
+ * callback.
+ */
+static void
+process_result (struct GNUNET_CHAT_Room *room,
+		const struct GNUNET_MessageHeader *reply)
+{
+  struct LeaveNotificationMessage *leave_msg;
+  struct JoinNotificationMessage *join_msg;
+  struct ReceiveNotificationMessage *received_msg;
+  struct ConfirmationReceiptMessage *receipt;
+  GNUNET_HashCode id;
+  struct GNUNET_CONTAINER_MetaData *meta;
+  struct GNUNET_CHAT_SendReceiptContext *src;
+  struct MemberList *pos;
+  struct MemberList *prev;
+  struct GNUNET_CRYPTO_AesSessionKey key;
+  char decrypted_msg[MAX_MESSAGE_LENGTH];
+  uint16_t size;
+  uint16_t meta_len;
+  uint16_t msg_len;
+  char *message_content;
+
+  size = ntohs (reply->size);
+  switch (ntohs (reply->type))
+    {
+    case GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION:
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got a join notification\n");
+#endif
+      if (size < sizeof (struct JoinNotificationMessage))
+	{
+	  GNUNET_break (0);
+	  return;
+	}
+      join_msg = (struct JoinNotificationMessage *) reply;
+      meta_len = size - sizeof (struct JoinNotificationMessage);
+      meta =
+	GNUNET_CONTAINER_meta_data_deserialize ((const char *) &join_msg[1],
+						meta_len);
+      if (NULL == meta)
+	{
+	  GNUNET_break (0);
+	  return;
+	}
+      pos = GNUNET_malloc (sizeof (struct MemberList));
+      pos->meta = meta;
+      GNUNET_CRYPTO_hash (&join_msg->public_key,
+			  sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+			  &pos->id);
+      GNUNET_PSEUDONYM_add (room->cfg, &pos->id, meta);
+      room->member_list_callback (room->member_list_callback_cls,
+				  meta, &join_msg->public_key,
+				  ntohl (join_msg->msg_options));
+      pos->next = room->members;
+      room->members = pos;
+      break;
+    case GNUNET_MESSAGE_TYPE_CHAT_LEAVE_NOTIFICATION:
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got a leave notification\n");
+#endif
+      if (size < sizeof (struct LeaveNotificationMessage))
+	{
+	  GNUNET_break (0);
+	  return;
+	}
+      leave_msg = (struct LeaveNotificationMessage *) reply;
+      room->member_list_callback (room->member_list_callback_cls,
+				  NULL, &leave_msg->user,
+				  GNUNET_CHAT_MSG_OPTION_NONE);
+      GNUNET_CRYPTO_hash (&leave_msg->user,
+			  sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+			  &id);
+      prev = NULL;
+      pos = room->members;
+      while ((NULL != pos) &&
+	     (0 != memcmp (&pos->id, &id, sizeof (GNUNET_HashCode))))
+	{
+	  prev = pos;
+	  pos = pos->next;
+	}
+      GNUNET_assert (NULL != pos);
+      if (NULL == prev)
+	room->members = pos->next;
+      else
+	prev->next = pos->next;
+      GNUNET_CONTAINER_meta_data_destroy (pos->meta);
+      GNUNET_free (pos);
+      break;
+    case GNUNET_MESSAGE_TYPE_CHAT_MESSAGE_NOTIFICATION:
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got a message notification\n");
+#endif
+      if (size <= sizeof (struct ReceiveNotificationMessage))
+	{
+	  GNUNET_break (0);
+	  return;
+	}
+      received_msg = (struct ReceiveNotificationMessage *) reply;
+      if (0 !=
+	  (ntohl (received_msg->msg_options) & GNUNET_CHAT_MSG_ACKNOWLEDGED))
+	{
+	  src = GNUNET_malloc (sizeof (struct GNUNET_CHAT_SendReceiptContext));
+	  src->chat_room = room;
+	  src->received_msg = GNUNET_memdup (received_msg, size);
+	  GNUNET_CLIENT_notify_transmit_ready (room->client,
+					       sizeof (struct ConfirmationReceiptMessage),
+					       GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+					       GNUNET_YES,
+					       &transmit_acknowledge_request,
+					       src);
+	}
+      msg_len = size - sizeof (struct ReceiveNotificationMessage);
+      if (0 !=
+	  (ntohl (received_msg->msg_options) & GNUNET_CHAT_MSG_PRIVATE))
+	{
+	  if (-1 == GNUNET_CRYPTO_rsa_decrypt (room->my_private_key,
+					       &received_msg->encrypted_key,
+					       &key,
+					       sizeof (struct GNUNET_CRYPTO_AesSessionKey)))
+	    {
+	      GNUNET_break (0);
+	      return;
+	    }
+	  msg_len = GNUNET_CRYPTO_aes_decrypt (&received_msg[1],
+					       msg_len,
+					       &key,
+					       (const struct GNUNET_CRYPTO_AesInitializationVector *) INITVALUE,
+					       decrypted_msg);
+	  message_content = decrypted_msg;
+	}
+      else
+	{
+	  message_content = GNUNET_malloc (msg_len + 1);
+	  memcpy (message_content, &received_msg[1], msg_len);
+	}
+      message_content[msg_len] = '\0';
+      pos = room->members;
+      while ((NULL != pos) &&
+	     (0 != memcmp (&pos->id,
+			   &received_msg->sender,
+			   sizeof (GNUNET_HashCode))))
+	pos = pos->next;
+      GNUNET_assert (NULL != pos);
+      room->message_callback (room->message_callback_cls,
+			      room,
+			      &received_msg->sender,
+			      pos->meta,
+			      message_content,
+			      ntohl (received_msg->msg_options));
+      if (message_content != decrypted_msg)
+	GNUNET_free (message_content);
+      break;
+    case GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_NOTIFICATION:
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got a confirmation receipt\n");
+#endif
+      if (size < sizeof (struct ConfirmationReceiptMessage))
+	{
+	  GNUNET_break (0);
+	  return;
+	}
+      receipt = (struct ConfirmationReceiptMessage *) reply;
+      if (NULL != room->confirmation_callback)
+	room->confirmation_callback (room->confirmation_cls,
+				     room,
+				     ntohl (receipt->sequence_number),
+				     GNUNET_TIME_absolute_ntoh (receipt->timestamp),
+				     &receipt->target,
+				     &receipt->content,
+				     &receipt->signature);
+      break;
+    default:
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Unknown message type: '%u'\n"), ntohs (reply->type));
+      GNUNET_break_op (0);
+      break;
+    }
+}
+
+
+/**
+ * Listen for incoming messages on this chat room.  Also, support servers going
+ * away/coming back (i.e. rejoin chat room to keep server state up to date).
+ *
+ * @param cls closure, pointer to the 'struct GNUNET_CHAT_Room'
+ * @param msg message received, NULL on timeout or fatal error
+ */
+static void 
+receive_results (void *cls,
+		 const struct GNUNET_MessageHeader *msg)
+{
+  struct GNUNET_CHAT_Room *chat_room = cls;
+
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got a message from the service\n");
+#endif
+  if (0 != (GNUNET_SCHEDULER_REASON_SHUTDOWN & GNUNET_SCHEDULER_get_reason ()))
+    return;
+  if (NULL == msg)
+    {
+      GNUNET_break (0);
+      GNUNET_CHAT_rejoin_room (chat_room);
+      return;
+    }
+  process_result (chat_room, msg);
+  if (NULL == chat_room->client)
+    return; /* fatal error */
+  /* continue receiving */
+  GNUNET_CLIENT_receive (chat_room->client,
+			 &receive_results,
+			 chat_room,
+			 GNUNET_TIME_UNIT_FOREVER_REL);
+}
+
+
+/**
+ * Read existing private key from file or create a new one if it does not exist
+ * yet.
+ * Returns the private key on success, NULL on error.
+ */
+static struct GNUNET_CRYPTO_RsaPrivateKey *
+GNUNET_CHAT_initPrivateKey (const struct GNUNET_CONFIGURATION_Handle *cfg,
+			    const char *nick_name)
+{
+  char *home;
+  char *keyfile;
+  struct GNUNET_CRYPTO_RsaPrivateKey *privKey;
+
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Initializing private key\n");
+#endif
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg,
+					       "chat",
+					       "HOME",
+					       &home))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Configuration option `%s' in section `%s' missing\n"),
+		  "HOME",
+		  "chat");
+      return NULL;
+    }
+  GNUNET_DISK_directory_create (home);
+  if (GNUNET_OK != GNUNET_DISK_directory_test (home))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Failed to access chat home directory `%s'\n"),
+		  home);
+      GNUNET_free (home);
+      return NULL;
+    }
+  /* read or create private key */
+  keyfile =
+    GNUNET_malloc (strlen (home) + strlen (NICK_IDENTITY_PREFIX) +
+		   strlen (nick_name) + 2);
+  strcpy (keyfile, home);
+  GNUNET_free (home);
+  if (keyfile[strlen (keyfile) - 1] != DIR_SEPARATOR)
+    strcat (keyfile, DIR_SEPARATOR_STR);
+  strcat (keyfile, NICK_IDENTITY_PREFIX);
+  strcat (keyfile, nick_name);
+  privKey = GNUNET_CRYPTO_rsa_key_create_from_file (keyfile);
+  if (NULL == privKey)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Failed to create/open key in file `%s'\n"),
+		  keyfile);
+    }
+  GNUNET_free (keyfile);
+  return privKey;
+}
+
+
+/**
+ * Transmit a join request to the chat service.
+ *
+ * @param cls closure, pointer to the 'struct GNUNET_CHAT_Room'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_join_request (void *cls,
+		       size_t size, 
+		       void *buf)
+{
+  struct GNUNET_CHAT_Room *chat_room = cls;
+  struct JoinRequestMessage *join_msg;
+  char *room;
+  char *meta;
+  size_t room_len;
+  ssize_t meta_len;
+  size_t size_of_join;
+
+  if (NULL == buf)
+    {
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Could not transmit join request\n");
+#endif
+      return 0;
+    }
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting join request to the service\n");
+#endif
+  room_len = strlen (chat_room->room_name);
+  meta_len = GNUNET_CONTAINER_meta_data_get_serialized_size (chat_room->member_info);
+  size_of_join = sizeof (struct JoinRequestMessage) + meta_len + room_len;
+  GNUNET_assert (size >= size_of_join);
+  join_msg = buf;
+  join_msg->header.size = htons (size);
+  join_msg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_JOIN_REQUEST);
+  join_msg->msg_options = htonl (chat_room->msg_options);
+  join_msg->room_name_len = htons (room_len);
+  join_msg->reserved = htons (0);
+  GNUNET_CRYPTO_rsa_key_get_public (chat_room->my_private_key, &join_msg->public_key);
+  room = (char *) &join_msg[1];
+  memcpy (room, chat_room->room_name, room_len);
+  meta = &room[room_len];
+  if (GNUNET_SYSERR ==
+      GNUNET_CONTAINER_meta_data_serialize (chat_room->member_info,
+					    &meta,
+					    meta_len,
+					    GNUNET_CONTAINER_META_DATA_SERIALIZE_FULL))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Could not serialize metadata\n"));
+      return 0;
+    }
+  return size_of_join;
+}
+
+
+/**
+ * Ask to send a join request.
+ */
+static int
+GNUNET_CHAT_rejoin_room (struct GNUNET_CHAT_Room *chat_room)
+{
+  size_t size_of_join;
+
+  size_of_join = sizeof (struct JoinRequestMessage) +
+    GNUNET_CONTAINER_meta_data_get_serialized_size (chat_room->member_info) +
+    strlen (chat_room->room_name);
+  if (NULL ==
+      GNUNET_CLIENT_notify_transmit_ready (chat_room->client,
+					   size_of_join,
+					   GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+					   GNUNET_YES,
+					   &transmit_join_request,
+					   chat_room))
+    return GNUNET_SYSERR;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Leave a chat room.
+ */
+void
+GNUNET_CHAT_leave_room (struct GNUNET_CHAT_Room *chat_room)
+{
+  struct MemberList *pos;
+
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Leaving the room '%s'\n", chat_room->room_name);
+#endif
+  GNUNET_CLIENT_disconnect (chat_room->client, GNUNET_NO);
+  GNUNET_free (chat_room->room_name);
+  GNUNET_CONTAINER_meta_data_destroy (chat_room->member_info);
+  GNUNET_CRYPTO_rsa_key_free (chat_room->my_private_key);
+  while (NULL != chat_room->members)
+    {
+      pos = chat_room->members;
+      chat_room->members = pos->next;
+      GNUNET_CONTAINER_meta_data_destroy (pos->meta);
+      GNUNET_free (pos);
+    }
+  GNUNET_free (chat_room);
+}
+
+
+/**
+ * Join a chat room.
+ *
+ * @param cfg configuration
+ * @param nick_name nickname of the user joining (used to
+ *                  determine which public key to use);
+ *                  the nickname should probably also
+ *                  be used in the member_info (as "EXTRACTOR_TITLE")
+ * @param member_info information about the joining member
+ * @param room_name name of the room
+ * @param msg_options message options of the joining user
+ * @param messageCallback which function to call if a message has
+ *        been received?
+ * @param message_cls argument to callback
+ * @param memberCallback which function to call for join/leave notifications
+ * @param member_cls argument to callback
+ * @param confirmationCallback which function to call for confirmations (maybe NULL)
+ * @param confirmation_cls argument to callback
+ * @param me member ID (pseudonym)
+ * @return NULL on error
+ */
+struct GNUNET_CHAT_Room *
+GNUNET_CHAT_join_room (const struct GNUNET_CONFIGURATION_Handle *cfg,
+		       const char *nick_name,
+		       struct GNUNET_CONTAINER_MetaData *member_info,
+		       const char *room_name,
+		       enum GNUNET_CHAT_MsgOptions msg_options,
+		       GNUNET_CHAT_MessageCallback messageCallback,
+		       void *message_cls,
+		       GNUNET_CHAT_MemberListCallback memberCallback,
+		       void *member_cls,
+		       GNUNET_CHAT_MessageConfirmation confirmationCallback,
+		       void *confirmation_cls,
+		       GNUNET_HashCode *me)
+{
+  struct GNUNET_CHAT_Room *chat_room;
+  struct GNUNET_CRYPTO_RsaPrivateKey *priv_key;
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded pub_key;
+  struct GNUNET_CLIENT_Connection *client;
+
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Joining the room '%s'\n", room_name);
+#endif
+  priv_key = GNUNET_CHAT_initPrivateKey (cfg, nick_name);
+  if (NULL == priv_key)
+    return NULL;
+  GNUNET_CRYPTO_rsa_key_get_public (priv_key, &pub_key);
+  GNUNET_CRYPTO_hash (&pub_key,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      me);
+  GNUNET_PSEUDONYM_add (cfg, me, member_info);
+  client = GNUNET_CLIENT_connect ("chat", cfg);
+  if (NULL == client)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  _("Failed to connect to the chat service\n"));
+      return NULL;
+    }
+  chat_room = GNUNET_malloc (sizeof (struct GNUNET_CHAT_Room));
+  chat_room->msg_options = msg_options;
+  chat_room->room_name = GNUNET_strdup (room_name);
+  chat_room->member_info = GNUNET_CONTAINER_meta_data_duplicate (member_info);
+  chat_room->my_private_key = priv_key;
+  chat_room->message_callback = messageCallback;
+  chat_room->message_callback_cls = message_cls;
+  chat_room->member_list_callback = memberCallback;
+  chat_room->member_list_callback_cls = member_cls;
+  chat_room->confirmation_callback = confirmationCallback;
+  chat_room->confirmation_cls = confirmation_cls;
+  chat_room->cfg = cfg;
+  chat_room->client = client;
+  chat_room->members = NULL;
+  GNUNET_CLIENT_receive (client,
+			 &receive_results,
+			 chat_room,
+			 GNUNET_TIME_UNIT_FOREVER_REL);
+  if (GNUNET_SYSERR == GNUNET_CHAT_rejoin_room (chat_room))
+    {
+      GNUNET_CHAT_leave_room (chat_room);
+      return NULL;
+    }
+  return chat_room;
+}
+
+
+/**
+ * Transmit a send-message request to the chat service.
+ *
+ * @param cls closure, pointer to the 'struct GNUNET_CHAT_SendMessageContext'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_send_request (void *cls,
+		       size_t size, 
+		       void *buf)
+{
+  struct GNUNET_CHAT_SendMessageContext *smc = cls;
+  struct TransmitRequestMessage *msg_to_send;
+  size_t msg_size;
+
+  if (NULL == buf)
+    {
+#if DEBUG_CHAT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Could not transmit a chat message\n");
+#endif
+      return 0;
+    }
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting a chat message to the service\n");
+#endif
+  msg_size = strlen (smc->message) + sizeof (struct TransmitRequestMessage);
+  GNUNET_assert (size >= msg_size);
+  msg_to_send = buf;
+  msg_to_send->header.size = htons (msg_size);
+  msg_to_send->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_TRANSMIT_REQUEST);
+  msg_to_send->msg_options = htonl (smc->options);
+  msg_to_send->sequence_number = htonl (smc->sequence_number);
+  msg_to_send->reserved = htonl (0);
+  if (NULL == smc->receiver)
+    memset (&msg_to_send->target, 0, sizeof (GNUNET_HashCode));
+  else
+    GNUNET_CRYPTO_hash (smc->receiver,
+			sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+			&msg_to_send->target);
+  memcpy (&msg_to_send[1], smc->message, strlen (smc->message));
+  /**
+   * Client don't encode private messages since public keys of other members are
+   * stored on the service side.
+   */
+  if (smc->options & GNUNET_CHAT_MSG_AUTHENTICATED)
+    {
+      msg_to_send->purpose.purpose =
+	htonl (GNUNET_SIGNATURE_PURPOSE_CHAT_MESSAGE);
+      msg_to_send->purpose.size =
+	htonl (msg_size -
+	       sizeof (struct GNUNET_MessageHeader) -
+	       sizeof (struct GNUNET_CRYPTO_RsaSignature));
+      GNUNET_assert (GNUNET_OK == 
+		     GNUNET_CRYPTO_rsa_sign (smc->chat_room->my_private_key,
+					     &msg_to_send->purpose,
+					     &msg_to_send->signature));
+    }
+  GNUNET_free (smc->message);
+  GNUNET_free (smc);
+  return msg_size;
+}
+
+
+/**
+ * Send a message.
+ *
+ * @param room handle for the chat room
+ * @param message message to be sent
+ * @param options options for the message
+ * @param receiver use NULL to send to everyone in the room
+ * @param sequence_number where to write the sequence id of the message
+ */
+void
+GNUNET_CHAT_send_message (struct GNUNET_CHAT_Room *room,
+			  const char *message,
+			  enum GNUNET_CHAT_MsgOptions options,
+			  const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *receiver,
+			  uint32_t *sequence_number)
+{
+  size_t msg_size;
+  struct GNUNET_CHAT_SendMessageContext *smc;
+
+#if DEBUG_CHAT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sending a message\n");
+#endif
+  *sequence_number = ++room->sequence_number;
+  smc = GNUNET_malloc (sizeof (struct GNUNET_CHAT_SendMessageContext));
+  smc->chat_room = room;
+  smc->message = GNUNET_strdup (message);
+  smc->options = options;
+  smc->receiver = receiver;
+  smc->sequence_number = *sequence_number;
+  msg_size = strlen (message) + sizeof (struct TransmitRequestMessage);
+  GNUNET_CLIENT_notify_transmit_ready (room->client,
+				       msg_size,
+				       GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+				       GNUNET_YES,
+				       &transmit_send_request,
+				       smc);
+}
+
+/* end of chat.c */
Index: src/chat/chat.h
===================================================================
--- src/chat/chat.h	(revision 0)
+++ src/chat/chat.h	(revision 0)
@@ -0,0 +1,458 @@
+/*
+     This file is part of GNUnet
+     (C) 2008, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 2, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file chat/chat.h
+ * @brief support for chat
+ * @author Christian Grothoff
+ * @author Nathan Evans
+ * @author Vitaly Minko
+ */
+
+#ifndef CHAT_H
+#define CHAT_H
+
+#include "gnunet_chat_service.h"
+
+/**
+ * Constant IV since we generate a new session key per each message.
+ */
+#define INITVALUE "InitializationVectorValue"
+
+
+/**
+ * Client-service messages
+ */
+
+/**
+ * Notification sent by service to client indicating that we've received a chat
+ * message.  After this struct, the remaining bytes are the actual text message.
+ * If the mesasge is private, then the text is encrypted, otherwise it's
+ * plaintext.
+ */
+struct ReceiveNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_MESSAGE_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Message options, see GNUNET_CHAT_MsgOptions.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Sequence number of the message (unique per sender).
+   */
+  uint32_t sequence_number GNUNET_PACKED;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Hash of the public key of the pseudonym of the sender of the message.
+   * TBD: Should be all zeros for anonymous.
+   */
+  GNUNET_HashCode sender;
+
+  /**
+   * The encrypted session key.
+   */
+  struct GNUNET_CRYPTO_RsaEncryptedData encrypted_key;
+
+};
+
+
+/**
+ * Request sent by client to transmit a chat message to another room members.
+ * After this struct, the remaining bytes are the actual message in plaintext.
+ * Private messages are encrypted on the service side.
+ */
+struct TransmitRequestMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_TRANSMIT_REQUEST
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Signature confirming receipt.  Signature covers everything from header
+   * through content.
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+
+  /**
+   * What is being signed and why?
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * Desired message options, see GNUNET_CHAT_MsgOptions.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Sequence number of the message (unique per sender).
+   */
+  uint32_t sequence_number GNUNET_PACKED;
+
+  /**
+   * Who should receive this message?  Set to all zeros for "everyone".
+   */
+  GNUNET_HashCode target;
+
+};
+
+
+/**
+ * Receipt sent from a message receiver to the service to confirm delivery of
+ * a chat message.
+ */
+struct ConfirmationReceiptMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_RECEIPT 
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Signature confirming receipt.  Signature covers everything from header
+   * through content.
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+
+  /**
+   * What is being signed and why?
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * Sequence number of the original message.
+   */
+  uint32_t sequence_number GNUNET_PACKED;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint32_t reserved2 GNUNET_PACKED;
+
+  /**
+   * Time of receipt.
+   */
+  struct GNUNET_TIME_AbsoluteNBO timestamp;
+
+  /**
+   * Who is confirming the receipt?
+   */
+  GNUNET_HashCode target;
+
+  /**
+   * Who is the author of the chat message?
+   */
+  GNUNET_HashCode author;
+
+  /**
+   * Hash of the (possibly encrypted) content.
+   */
+  GNUNET_HashCode content;
+
+};
+
+
+/**
+ * Message send from client to daemon to join a chat room.
+ * This struct is followed by the room name and then
+ * the serialized ECRS meta data describing the new member.
+ */
+struct JoinRequestMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_JOIN_REQUEST
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Options.  Set all options that this client is willing to receive.
+   * For example, if the client does not want to receive anonymous or
+   * OTR messages but is willing to generate acknowledgements and
+   * receive private messages, this should be set to
+   * GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ACKNOWLEDGED.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Length of the room name.
+   */
+  uint16_t room_name_len GNUNET_PACKED;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint16_t reserved GNUNET_PACKED;
+  uint32_t reserved2 GNUNET_PACKED;
+
+  /**
+   * Public key of the joining member.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+};
+
+
+/**
+ * Message send by server to client to indicate joining of another room member.
+ * This struct is followed by the serialized ECRS MetaData describing the new
+ * member.
+ */
+struct JoinNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Options.  Set to all options that the new user is willing to
+   * process.  For example, if the client does not want to receive
+   * anonymous or OTR messages but is willing to generate
+   * acknowledgements and receive private messages, this should be set
+   * to GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ACKNOWLEDGED.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Public key of the new user.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+};
+
+
+/**
+ * Message send by server to client to indicate leaving of another room member.
+ */
+struct LeaveNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_LEAVE_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Reserved (for alignment).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Who is leaving?
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded user;
+
+};
+
+
+/**
+ * Peer-to-peer messages
+ */
+
+/**
+ * Message send by one peer to another to indicate joining of another room
+ * member.  This struct is followed by the room name and then the serialized
+ * ECRS MetaData describing the new member.
+ */
+struct P2PJoinNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_P2P_JOIN_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Options.  Set all options that this client is willing to receive.
+   * For example, if the client does not want to receive anonymous or
+   * OTR messages but is willing to generate acknowledgements and
+   * receive private messages, this should be set to
+   * GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ACKNOWLEDGED.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Length of the room name.
+   */
+  uint16_t room_name_len GNUNET_PACKED;
+
+  /**
+   * Reserved (should be zero).
+   */
+  uint16_t reserved GNUNET_PACKED;
+  uint32_t reserved2 GNUNET_PACKED;
+
+  /**
+   * Public key of the joining member.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+};
+
+
+/**
+ * Message send by one peer to another to indicate leaving of another room
+ * member.
+ */
+struct P2PLeaveNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_P2P_LEAVE_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Reserved (for alignment).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Who is leaving?
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded user;
+
+};
+
+
+/**
+ * Message send by one peer to another to indicate receiving of a chat message.
+ * After this struct, the remaining bytes are the actual text message.  If the
+ * mesasge is private, then the text is encrypted, otherwise it's plaintext.
+ */
+struct P2PReceiveNotificationMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_P2P_MESSAGE_NOTIFICATION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Message options, see GNUNET_CHAT_MsgOptions.
+   */
+  uint32_t msg_options GNUNET_PACKED;
+
+  /**
+   * Sequence number of the message (unique per sender).
+   */
+  uint32_t sequence_number GNUNET_PACKED;
+
+  /**
+   * Reserved (for alignment).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Hash of the public key of the pseudonym of the sender of the message
+   * TBD: Should be all zeros for anonymous.
+   */
+  GNUNET_HashCode sender;
+
+  /**
+   * Who should receive this message?  Set to all zeros for "everyone".
+   */
+  GNUNET_HashCode target;
+
+  /**
+   * The encrypted session key.
+   */
+  struct GNUNET_CRYPTO_RsaEncryptedData encrypted_key;
+
+};
+
+
+/**
+ * Receipt sent from one peer to another to confirm delivery of a chat message.
+ */
+struct P2PConfirmationReceiptMessage
+{
+  /**
+   * Message type will be GNUNET_MESSAGE_TYPE_CHAT_P2P_CONFIRMATION_RECEIPT
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * For alignment (should be zero).
+   */
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Signature confirming receipt.  Signature covers everything from header
+   * through content.
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+
+  /**
+   * What is being signed and why?
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * Sequence number of the original message.
+   */
+  uint32_t msg_sequence_number GNUNET_PACKED;
+
+  /**
+   * Sequence number of the receipt.
+   */
+  uint32_t sequence_number GNUNET_PACKED;
+
+  /**
+   * Time of receipt.
+   */
+  struct GNUNET_TIME_AbsoluteNBO timestamp;
+
+  /**
+   * Who is confirming the receipt?
+   */
+  GNUNET_HashCode target;
+
+  /**
+   * Who is the author of the chat message?
+   */
+  GNUNET_HashCode author;
+
+  /**
+   * Hash of the (possibly encrypted) content.
+   */
+  GNUNET_HashCode content;
+
+};
+
+#endif
+
+/* end of chat.h */
Index: src/chat/Makefile.am
===================================================================
--- src/chat/Makefile.am	(revision 0)
+++ src/chat/Makefile.am	(revision 0)
@@ -0,0 +1,39 @@
+INCLUDES = -I$(top_srcdir)/src/include
+
+if MINGW
+ WINFLAGS = -Wl,--no-undefined -Wl,--export-all-symbols 
+endif
+
+if USE_COVERAGE
+  AM_CFLAGS = -fprofile-arcs -ftest-coverage
+endif
+
+lib_LTLIBRARIES = libgnunetchat.la
+
+libgnunetchat_la_SOURCES = \
+  chat.c chat.h
+
+libgnunetchat_la_LIBADD = \
+  $(top_builddir)/src/util/libgnunetutil.la
+
+libgnunetchat_la_LDFLAGS = \
+  $(GN_LIB_LDFLAGS)  $(WINFLAGS) \
+  -version-info 0:0:0
+
+bin_PROGRAMS = \
+ gnunet-service-chat \
+ gnunet-chat
+
+gnunet_service_chat_SOURCES = \
+ gnunet-service-chat.c         
+gnunet_service_chat_LDADD = \
+  $(top_builddir)/src/core/libgnunetcore.la \
+  $(top_builddir)/src/util/libgnunetutil.la \
+  $(GN_LIBINTL)
+
+gnunet_chat_SOURCES = \
+ gnunet-chat.c         
+gnunet_chat_LDADD = \
+  $(top_builddir)/src/chat/libgnunetchat.la \
+  $(top_builddir)/src/util/libgnunetutil.la \
+  $(GN_LIBINTL)
Index: src/chat/gnunet-service-chat.c
===================================================================
--- src/chat/gnunet-service-chat.c	(revision 0)
+++ src/chat/gnunet-service-chat.c	(revision 0)
@@ -0,0 +1,1565 @@
+/*
+     This file is part of GNUnet.
+     (C) 2009, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file chat/gnunet-service-caht.c
+ * @brief program that tracks template
+ * @author Christian Grothoff
+ * @author Vitaly Minko
+ */
+
+#include "platform.h"
+#include "gnunet_core_service.h"
+#include "gnunet_crypto_lib.h"
+#include "gnunet_protocols.h"
+#include "gnunet_service_lib.h"
+#include "gnunet_signatures.h"
+#include "chat.h"
+
+#define DEBUG_CHAT_SERVICE GNUNET_YES
+#define MAX_TRANSMIT_DELAY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 60)
+#define QUEUE_SIZE 16
+
+
+/**
+ * Linked list of our current clients.
+ */
+struct ChatClient
+{
+  struct ChatClient *next;
+
+  /**
+   * Handle for a chat client (NULL for external clients).
+   */
+  struct GNUNET_SERVER_Client *client;
+
+  /**
+   * Public key of the client.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+  /**
+   * Name of the room which the client is in.
+   */
+  char *room;
+
+  /**
+   * Serialized metadata of the client.
+   */
+  char *member_info;
+
+  /**
+   * Hash of the public key (for convenience).
+   */
+  GNUNET_HashCode id;
+
+  /**
+   * Options which the client is willing to receive.
+   */
+  uint32_t msg_options;
+
+  /**
+   * Length of serialized metadata in member_info.
+   */
+  uint16_t meta_len;
+
+  /**
+   * Sequence number of the last message sent by the client.
+   */
+  uint32_t msg_sequence_number;
+
+  /**
+   * Sequence number of the last receipt sent by the client.
+   * Used to discard already processed receipts.
+   */
+  uint32_t rcpt_sequence_number;
+
+};
+
+
+/**
+ * Handle to the core service (NULL until we've connected to it).
+ */
+static struct GNUNET_CORE_Handle *core;
+
+/**
+ * Our configuration.
+ */
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+/**
+ * The identity of this host.
+ */
+static const struct GNUNET_PeerIdentity *me;
+
+/**
+ * Head of the list of current clients.
+ */
+static struct ChatClient *client_list_head = NULL;
+
+/**
+ * Notification context containing all connected clients.
+ */
+struct GNUNET_SERVER_NotificationContext *nc = NULL;
+
+
+/**
+ * Transmit a message notification to the peer.
+ *
+ * @param cls closure, pointer to the 'struct P2PReceiveNotificationMessage'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_message_notification_to_peer (void *cls,
+				       size_t size,
+				       void *buf)
+{
+  struct P2PReceiveNotificationMessage *my_msg = cls;
+  struct P2PReceiveNotificationMessage *m = buf;
+  size_t msg_size;
+
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting P2P message notification\n");
+#endif
+  msg_size = ntohs (my_msg->header.size);
+  GNUNET_assert (size >= msg_size);
+  GNUNET_assert (NULL != buf);
+  memcpy (m, my_msg, msg_size);
+  GNUNET_free (my_msg);
+  return msg_size;
+}
+
+
+/**
+ * Ask to send a message notification to the peer.
+ */
+static void
+send_message_noficiation (void *cls,
+			  const struct GNUNET_PeerIdentity *peer,
+			  const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct P2PReceiveNotificationMessage *msg = cls;
+  struct P2PReceiveNotificationMessage *my_msg;
+  struct GNUNET_CORE_TransmitHandle *th;
+
+  if (NULL == peer)
+    GNUNET_free (msg);
+  else
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Sending message notification to `%s'\n", GNUNET_i2s (peer));
+#endif
+      my_msg = GNUNET_memdup (msg, ntohs (msg->header.size));
+      th = GNUNET_CORE_notify_transmit_ready (core,
+					      1,
+					      MAX_TRANSMIT_DELAY,
+					      peer,
+					      ntohs (msg->header.size),
+					      &transmit_message_notification_to_peer,
+					      my_msg);
+      GNUNET_assert (NULL != th);
+    }
+}
+
+
+/**
+ * A client sent a chat message.  Encrypt the message text if the message is
+ * private.  Send the message to local room members and to all connected peers.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_transmit_request (void *cls,
+			 struct GNUNET_SERVER_Client *client,
+			 const struct GNUNET_MessageHeader *message)
+{
+  static GNUNET_HashCode all_zeros;
+  const struct TransmitRequestMessage *trmsg;
+  struct ReceiveNotificationMessage *rnmsg;
+  struct P2PReceiveNotificationMessage *p2p_rnmsg;
+  struct ChatClient *pos;
+  struct ChatClient *target;
+  struct GNUNET_CRYPTO_AesSessionKey key;
+  char encrypted_msg[MAX_MESSAGE_LENGTH];
+  const char *room;
+  int msg_len;
+  int priv_msg;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Client sent a chat message\n");
+  if (ntohs (message->size) <= sizeof (struct TransmitRequestMessage))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Malformed message: wrong size\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;
+    }
+  trmsg = (const struct TransmitRequestMessage *) message;
+  msg_len = ntohs (trmsg->header.size) - sizeof (struct TransmitRequestMessage);
+  priv_msg = (ntohl (trmsg->msg_options) & GNUNET_CHAT_MSG_PRIVATE) != 0;
+  if (priv_msg)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Encrypting the message text\n");
+#endif
+      GNUNET_CRYPTO_aes_create_session_key (&key);
+      msg_len = GNUNET_CRYPTO_aes_encrypt (&trmsg[1],
+					   msg_len,
+					   &key,
+					   (const struct GNUNET_CRYPTO_AesInitializationVector *) INITVALUE,
+					   encrypted_msg);
+      if (-1 == msg_len)
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Could not encrypt the message text\n");
+	  GNUNET_break (0);
+	  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+	  return;
+	}
+    }
+  rnmsg = GNUNET_malloc (sizeof (struct ReceiveNotificationMessage) + msg_len);
+  rnmsg->header.size = htons (sizeof (struct ReceiveNotificationMessage) +
+			      msg_len);
+  rnmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_MESSAGE_NOTIFICATION);
+  rnmsg->msg_options = trmsg->msg_options;
+  rnmsg->sequence_number = trmsg->sequence_number;
+  pos = client_list_head;
+  while ((NULL != pos) && (pos->client != client))
+    pos = pos->next;
+  if (NULL == pos)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "The client is not a member of a chat room. Client has to "
+		  "join a chat room first\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      GNUNET_free (rnmsg);
+      return;
+    }
+  room = pos->room;
+  pos->msg_sequence_number = ntohl (trmsg->sequence_number);
+  if (0 == (ntohl (trmsg->msg_options) & GNUNET_CHAT_MSG_ANONYMOUS))
+    rnmsg->sender = pos->id;
+  else
+    memset (&rnmsg->sender, 0, sizeof (GNUNET_HashCode));
+  if (priv_msg)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Encrypting the session key using the public key of '%s'\n",
+		  GNUNET_h2s (&trmsg->target));
+#endif
+      if (0 == memcmp (&all_zeros, &trmsg->target, sizeof (GNUNET_HashCode)))
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Malformed message: private, but no target\n");
+	  GNUNET_break (0);
+	  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+	  GNUNET_free (rnmsg);
+	  return;
+	}
+      memcpy (&rnmsg[1], encrypted_msg, msg_len);
+      target = client_list_head;
+      while ((NULL != target) &&
+	     (0 != memcmp (&target->id,
+			   &trmsg->target,
+			   sizeof (GNUNET_HashCode))))
+	target = target->next;
+      if (NULL == target)
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Unknown target of the private message\n");
+	  GNUNET_break (0);
+	  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+	  GNUNET_free (rnmsg);
+	  return;
+	}
+      if (GNUNET_SYSERR == GNUNET_CRYPTO_rsa_encrypt (&key,
+						      sizeof (struct GNUNET_CRYPTO_AesSessionKey),
+						      &target->public_key,
+						      &rnmsg->encrypted_key))
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Could not encrypt the session key\n");
+	  GNUNET_break (0);
+	  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+	  GNUNET_free (rnmsg);
+	  return;
+	}
+    }
+  else
+    {
+      memcpy (&rnmsg[1], &trmsg[1], msg_len);
+    }
+  pos = client_list_head;
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sending message to local room members\n");
+#endif
+  while (NULL != pos)
+    {
+      if ((0 == strcmp (room, pos->room)) &&
+	  (NULL != pos->client) &&
+	  (pos->client != client))
+	{
+	  if (((!priv_msg) ||
+	       (0 == memcmp (&trmsg->target,
+			     &pos->id,
+			     sizeof (GNUNET_HashCode)))) &&
+	      (0 == (ntohl (trmsg->msg_options) & (~pos->msg_options))))
+	    {
+	      GNUNET_SERVER_notification_context_unicast (nc,
+							  pos->client,
+							  &rnmsg->header,
+							  GNUNET_NO);
+	    }
+	}
+      pos = pos->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting message to neighbour peers\n");
+#endif
+  p2p_rnmsg = GNUNET_malloc (sizeof (struct P2PReceiveNotificationMessage) +
+			     msg_len);
+  p2p_rnmsg->header.size = htons (sizeof (struct P2PReceiveNotificationMessage) +
+				  msg_len);
+  p2p_rnmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_P2P_MESSAGE_NOTIFICATION);
+  p2p_rnmsg->msg_options = trmsg->msg_options;
+  p2p_rnmsg->sequence_number = trmsg->sequence_number;
+  memcpy (&p2p_rnmsg->sender, &rnmsg->sender, sizeof (GNUNET_HashCode));
+  p2p_rnmsg->target = trmsg->target;
+  if (priv_msg)
+    {
+      memcpy (&p2p_rnmsg[1], encrypted_msg, msg_len);
+      memcpy (&p2p_rnmsg->encrypted_key,
+	      &rnmsg->encrypted_key,
+	      sizeof (struct GNUNET_CRYPTO_RsaEncryptedData));
+    }
+  else
+    {
+      memcpy (&p2p_rnmsg[1], &trmsg[1], msg_len);
+    }
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_message_noficiation,
+			     p2p_rnmsg);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  GNUNET_free (rnmsg);
+}
+
+
+/**
+ * Transmit a join notification to the peer.
+ *
+ * @param cls closure, pointer to the 'struct ChatClient'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_join_notification_to_peer (void *cls,
+				    size_t size,
+				    void *buf)
+{
+  struct ChatClient *entry = cls;
+  struct P2PJoinNotificationMessage *m = buf;
+  size_t room_len;
+  size_t meta_len;
+  size_t msg_size;
+  char *roomptr;
+
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting P2P join notification\n");
+#endif
+  room_len = strlen (entry->room);
+  meta_len = entry->meta_len;
+  msg_size = sizeof (struct P2PJoinNotificationMessage) + meta_len + room_len;
+  GNUNET_assert (size >= msg_size);
+  GNUNET_assert (NULL != buf);
+  m = buf;
+  m->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_P2P_JOIN_NOTIFICATION);
+  m->header.size = htons (msg_size);
+  m->msg_options = htonl (entry->msg_options);
+  m->room_name_len = htons (room_len);
+  m->reserved = htons (0);
+  m->public_key = entry->public_key;
+  roomptr = (char *) &m[1];
+  memcpy (roomptr, entry->room, room_len);
+  if (meta_len > 0)
+    memcpy (&roomptr[room_len], entry->member_info, meta_len);
+  return msg_size;
+}
+
+
+/**
+ * Ask to send a join notification to the peer.
+ */
+static void
+send_join_noficiation (void *cls,
+		       const struct GNUNET_PeerIdentity *peer,
+		       const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct ChatClient *entry = cls;
+  struct GNUNET_CORE_TransmitHandle *th;
+  size_t msg_size;
+
+  if (NULL != peer)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Sending join notification to `%s'\n", GNUNET_i2s (peer));
+#endif
+      msg_size = sizeof (struct P2PJoinNotificationMessage) +
+	strlen (entry->room) + 
+	entry->meta_len;
+      th = GNUNET_CORE_notify_transmit_ready (core,
+					      1,
+					      MAX_TRANSMIT_DELAY,
+					      peer,
+					      msg_size,
+					      &transmit_join_notification_to_peer,
+					      entry);
+      GNUNET_assert (NULL != th);
+    }
+}
+
+
+/**
+ * A client asked for entering a chat room.  Add the new member to the list of
+ * clients and notify remaining room members.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_join_request (void *cls,
+		     struct GNUNET_SERVER_Client *client,
+		     const struct GNUNET_MessageHeader *message)
+{
+  const struct JoinRequestMessage *jrmsg;
+  char *room_name;
+  const char *roomptr;
+  uint16_t header_size;
+  uint16_t meta_len;
+  uint16_t room_name_len;
+  struct ChatClient *new_entry;
+  struct ChatClient *entry;
+  struct JoinNotificationMessage *jnmsg;
+  struct JoinNotificationMessage *entry_jnmsg;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Client sent a join request\n");
+  if (ntohs (message->size) <= sizeof (struct JoinRequestMessage))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Malformed message: wrong size\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;
+    }
+  jrmsg = (const struct JoinRequestMessage *) message;
+  header_size = ntohs (jrmsg->header.size);
+  room_name_len = ntohs (jrmsg->room_name_len);
+  if (header_size - sizeof (struct JoinRequestMessage) <=
+      room_name_len)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Malformed message: wrong length of the room name\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;
+    }
+  meta_len =
+    header_size - sizeof (struct JoinRequestMessage) - room_name_len;
+  roomptr = (const char *) &jrmsg[1];
+  room_name = GNUNET_malloc (room_name_len + 1);
+  memcpy (room_name, roomptr, room_name_len);
+  room_name[room_name_len] = '\0';
+  new_entry = GNUNET_malloc (sizeof (struct ChatClient));
+  memset (new_entry, 0, sizeof (struct ChatClient));
+  new_entry->client = client;
+  new_entry->room = room_name;
+  new_entry->public_key = jrmsg->public_key;
+  new_entry->meta_len = meta_len;
+  if (meta_len > 0)
+    {
+      new_entry->member_info = GNUNET_malloc (meta_len);
+      memcpy (new_entry->member_info, &roomptr[room_name_len], meta_len);
+    }
+  else
+    new_entry->member_info = NULL;
+  GNUNET_CRYPTO_hash (&new_entry->public_key,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      &new_entry->id);
+  new_entry->msg_options = ntohl (jrmsg->msg_options);
+  new_entry->next = client_list_head;
+  client_list_head = new_entry;
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Synchronizing room members between local clients\n");
+#endif
+  jnmsg = GNUNET_malloc (sizeof (struct JoinNotificationMessage) + meta_len);
+  jnmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION);
+  jnmsg->header.size =
+    htons (sizeof (struct JoinNotificationMessage) + meta_len);
+  jnmsg->msg_options = jrmsg->msg_options;
+  jnmsg->public_key = new_entry->public_key;
+  memcpy (&jnmsg[1], &roomptr[room_name_len], meta_len);
+  GNUNET_SERVER_notification_context_add (nc, client);
+  entry = client_list_head;
+  while (NULL != entry)
+    {
+      if (0 == strcmp (room_name, entry->room))
+	{
+	  if (NULL != entry->client)
+	    GNUNET_SERVER_notification_context_unicast (nc,
+							entry->client,
+							&jnmsg->header,
+							GNUNET_NO);
+	  if (entry->client != client)
+	    {
+	      entry_jnmsg =
+		GNUNET_malloc (sizeof (struct JoinNotificationMessage) +
+			       entry->meta_len);
+	      entry_jnmsg->header.type =
+		htons (GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION);
+	      entry_jnmsg->header.size =
+		htons (sizeof (struct JoinNotificationMessage) +
+		       entry->meta_len);
+	      entry_jnmsg->msg_options = entry->msg_options;
+	      entry_jnmsg->public_key = entry->public_key;
+	      memcpy (&entry_jnmsg[1], entry->member_info, entry->meta_len);
+	      GNUNET_SERVER_notification_context_unicast (nc,
+							  client,
+							  &entry_jnmsg->header,
+							  GNUNET_NO);
+	      GNUNET_free (entry_jnmsg);
+	    }
+	}
+      entry = entry->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting join notification to neighbour peers\n");
+#endif
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_join_noficiation,
+			     new_entry);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  GNUNET_free (jnmsg);
+}
+
+/**
+ * Transmit a confirmation receipt to the peer.
+ *
+ * @param cls closure, pointer to the 'struct P2PConfirmationReceiptMessage'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_confirmation_receipt_to_peer (void *cls,
+				       size_t size,
+				       void *buf)
+{
+  struct P2PConfirmationReceiptMessage *receipt = cls;
+  size_t msg_size;
+
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting P2P confirmation receipt to '%s'\n",
+	      GNUNET_h2s (&receipt->target));
+#endif
+  msg_size = sizeof (struct P2PConfirmationReceiptMessage);
+  GNUNET_assert (size >= msg_size);
+  GNUNET_assert (NULL != buf);
+  memcpy (buf, receipt, msg_size);
+  GNUNET_free (receipt);
+  return msg_size;
+}
+
+
+/**
+ * Ask to send a confirmation receipt to the peer.
+ */
+static void
+send_confirmation_receipt (void *cls,
+			   const struct GNUNET_PeerIdentity *peer,
+			   const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct P2PConfirmationReceiptMessage *receipt = cls;
+  struct P2PConfirmationReceiptMessage *my_receipt;
+  struct GNUNET_CORE_TransmitHandle *th;
+  size_t msg_size;
+
+  if (NULL == peer)
+    GNUNET_free (receipt);
+  else
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Sending confirmation receipt to `%s'\n", GNUNET_i2s (peer));
+#endif
+      msg_size = sizeof (struct P2PConfirmationReceiptMessage);
+      my_receipt = GNUNET_memdup (receipt,
+				  sizeof (struct P2PConfirmationReceiptMessage));
+      th = GNUNET_CORE_notify_transmit_ready (core,
+					      1,
+					      MAX_TRANSMIT_DELAY,
+					      peer,
+					      msg_size,
+					      &transmit_confirmation_receipt_to_peer,
+					      my_receipt);
+      GNUNET_assert (NULL != th);
+    }
+}
+
+
+/**
+ * A client sent a confirmation receipt.  Broadcast the receipt to all connected
+ * peers if the author of the original message is a local client.  Otherwise
+ * check the signature and notify the user if the signature is valid.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_acknowledge_request (void *cls,
+			    struct GNUNET_SERVER_Client *client,
+			    const struct GNUNET_MessageHeader *message)
+{
+  const struct ConfirmationReceiptMessage *receipt;
+  struct ConfirmationReceiptMessage *crmsg;
+  struct P2PConfirmationReceiptMessage *p2p_crmsg;
+  struct ChatClient *target;
+  struct ChatClient *author;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Client sent a confirmation receipt\n");
+  receipt = (const struct ConfirmationReceiptMessage *) message;
+  author = client_list_head;
+  while ((NULL != author) &&
+	 (0 != memcmp (&receipt->author,
+		       &author->id,
+		       sizeof (GNUNET_HashCode))))
+    author = author->next;
+  if (NULL == author)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Unknown author of the original message\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;
+    }
+  target = client_list_head;
+  while ((NULL != target) &&
+	 (0 != memcmp (&receipt->target,
+		       &target->id,
+		       sizeof (GNUNET_HashCode))))
+    target = target->next;
+  if (NULL == target)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Unknown target of the confirmation receipt\n");
+      GNUNET_break (0);
+      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+      return;
+    }
+  if (NULL == author->client)
+    {
+      target->rcpt_sequence_number++;
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Broadcasting %s's receipt #%u to neighbour peers\n",
+		  GNUNET_h2s (&target->id), target->rcpt_sequence_number);
+#endif
+      p2p_crmsg = GNUNET_malloc (sizeof (struct P2PConfirmationReceiptMessage));
+      p2p_crmsg->header.size = htons (sizeof (struct P2PConfirmationReceiptMessage));
+      p2p_crmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_P2P_CONFIRMATION_RECEIPT);
+      p2p_crmsg->signature = receipt->signature;
+      p2p_crmsg->purpose = receipt->purpose;
+      p2p_crmsg->msg_sequence_number = receipt->sequence_number;
+      p2p_crmsg->timestamp = receipt->timestamp;
+      p2p_crmsg->target = receipt->target;
+      p2p_crmsg->author = receipt->author;
+      p2p_crmsg->content = receipt->content;
+      p2p_crmsg->sequence_number = htonl (target->rcpt_sequence_number);
+      GNUNET_CORE_iterate_peers (cfg,
+				 &send_confirmation_receipt,
+				 p2p_crmsg);
+    }
+  else
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Verifying signature of the receipt\n");
+#endif
+      if (GNUNET_OK !=
+	  GNUNET_CRYPTO_rsa_verify (GNUNET_SIGNATURE_PURPOSE_CHAT_RECEIPT,
+				    &receipt->purpose,
+				    &receipt->signature,
+				    &target->public_key))
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Invalid signature of the receipt\n");
+	  GNUNET_break (0);
+	  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+	  return;
+	}
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Sending receipt to the client which sent the original message\n");
+#endif
+      crmsg = GNUNET_memdup (receipt, sizeof (struct ConfirmationReceiptMessage));
+      crmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_NOTIFICATION);
+      GNUNET_SERVER_notification_context_unicast (nc,
+						  author->client,
+						  &crmsg->header,
+						  GNUNET_NO);
+      GNUNET_free (crmsg);
+    }
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Transmit a leave notification to the peer.
+ *
+ * @param cls closure, pointer to the
+ *        'struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded'
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_leave_notification_to_peer (void *cls,
+				     size_t size,
+				     void *buf)
+{
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *public_key = cls;
+  struct P2PLeaveNotificationMessage *m = buf;
+  size_t msg_size;
+
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Transmitting P2P leave notification\n");
+#endif
+  msg_size = sizeof (struct P2PLeaveNotificationMessage);
+  GNUNET_assert (size >= msg_size);
+  GNUNET_assert (NULL != buf);
+  m = buf;
+  m->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_P2P_LEAVE_NOTIFICATION);
+  m->header.size = htons (msg_size);
+  m->reserved = htons (0);
+  m->user = *public_key;
+  GNUNET_free (public_key);
+  return msg_size;
+}
+
+
+/**
+ * Ask to send a leave notification to the peer.
+ */
+static void
+send_leave_noficiation (void *cls,
+			const struct GNUNET_PeerIdentity *peer,
+			const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct ChatClient *entry = cls;
+  struct GNUNET_CORE_TransmitHandle *th;
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *public_key;
+  size_t msg_size;
+
+  if (NULL == peer)
+    {
+      GNUNET_free (entry->room);
+      GNUNET_free_non_null (entry->member_info);
+      GNUNET_free (entry);
+    }
+  else
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "Sending leave notification to `%s'\n", GNUNET_i2s (peer));
+#endif
+      msg_size = sizeof (struct P2PLeaveNotificationMessage);
+      public_key = GNUNET_memdup (&entry->public_key,
+				  sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded));
+      th = GNUNET_CORE_notify_transmit_ready (core,
+					      1,
+					      MAX_TRANSMIT_DELAY,
+					      peer,
+					      msg_size,
+					      &transmit_leave_notification_to_peer,
+					      public_key);
+      GNUNET_assert (NULL != th);
+    }
+}
+
+
+/**
+ * A client disconnected.  Remove all of its data structure entries and notify
+ * remaining room members.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ */
+static void
+handle_client_disconnect (void *cls,
+			  struct GNUNET_SERVER_Client *client)
+{
+  struct ChatClient *entry;
+  struct ChatClient *pos;
+  struct ChatClient *prev;
+  struct LeaveNotificationMessage lnmsg;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Client disconnected\n");
+  pos = client_list_head;
+  prev = NULL;
+  while ((NULL != pos) && (pos->client != client))
+    {
+      prev = pos;
+      pos = pos->next;
+    }
+  if (NULL == pos)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "No such client. There is nothing to do\n");
+#endif
+      return;
+    }
+  if (NULL == prev)
+    client_list_head = pos->next;
+  else
+    prev->next = pos->next;
+  entry = client_list_head;
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Notifying local room members that the client has disconnected\n");
+#endif
+  lnmsg.header.size = htons (sizeof (struct LeaveNotificationMessage));
+  lnmsg.header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_LEAVE_NOTIFICATION);
+  lnmsg.reserved = htonl (0);
+  lnmsg.user = pos->public_key;
+  while (NULL != entry)
+    {
+      if ((0 == strcmp (pos->room, entry->room)) &&
+	  (NULL != entry->client))
+	{
+	  GNUNET_SERVER_notification_context_unicast (nc,
+						      entry->client,
+						      &lnmsg.header,
+						      GNUNET_NO);
+	}
+      entry = entry->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting leave notification to neighbour peers\n");
+#endif
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_leave_noficiation,
+			     pos);
+}
+
+
+/**
+ * Handle P2P join notification.
+ *
+ * @param cls closure, always NULL
+ * @param other the other peer involved
+ * @param message the actual message
+ * @param atsi performance information
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_p2p_join_notification (void *cls,
+			      const struct GNUNET_PeerIdentity *other,
+			      const struct GNUNET_MessageHeader *message,
+			      const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  const struct P2PJoinNotificationMessage *p2p_jnmsg;
+  char *room_name;
+  const char *roomptr;
+  uint16_t header_size;
+  uint16_t meta_len;
+  uint16_t room_name_len;
+  struct ChatClient *new_entry;
+  struct ChatClient *entry;
+  struct JoinNotificationMessage *jnmsg;
+  GNUNET_HashCode id;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Got P2P join notification\n");
+  if (ntohs (message->size) <= sizeof (struct P2PJoinNotificationMessage))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Malformed message: wrong size\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+  p2p_jnmsg = (const struct P2PJoinNotificationMessage *) message;
+  header_size = ntohs (p2p_jnmsg->header.size);
+  room_name_len = ntohs (p2p_jnmsg->room_name_len);
+  if (header_size - sizeof (struct P2PJoinNotificationMessage) <=
+      room_name_len)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Malformed message: wrong length of the room name\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+  GNUNET_CRYPTO_hash (&p2p_jnmsg->public_key,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      &id);
+  entry = client_list_head;
+  while (NULL != entry)
+    {
+      if (0 == memcmp (&entry->id, &id, sizeof (GNUNET_HashCode)))
+	{
+#if DEBUG_CHAT_SERVICE
+	  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		      "The client has already joined. There is nothing to do\n");
+#endif
+	  return GNUNET_OK;
+	}
+      entry = entry->next;
+    }
+  meta_len =
+    header_size - sizeof (struct P2PJoinNotificationMessage) - room_name_len;
+  roomptr = (const char *) &p2p_jnmsg[1];
+  room_name = GNUNET_malloc (room_name_len + 1);
+  memcpy (room_name, roomptr, room_name_len);
+  room_name[room_name_len] = '\0';
+  new_entry = GNUNET_malloc (sizeof (struct ChatClient));
+  memset (new_entry, 0, sizeof (struct ChatClient));
+  new_entry->id = id;
+  new_entry->client = NULL;
+  new_entry->room = room_name;
+  new_entry->public_key = p2p_jnmsg->public_key;
+  new_entry->meta_len = meta_len;
+  if (meta_len > 0)
+    {
+      new_entry->member_info = GNUNET_malloc (meta_len);
+      memcpy (new_entry->member_info, &roomptr[room_name_len], meta_len);
+    }
+  else
+    new_entry->member_info = NULL;
+  new_entry->msg_options = ntohl (p2p_jnmsg->msg_options);
+  new_entry->next = client_list_head;
+  client_list_head = new_entry;
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Notifying local room members that we have a new client\n");
+#endif
+  jnmsg = GNUNET_malloc (sizeof (struct JoinNotificationMessage) + meta_len);
+  jnmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION);
+  jnmsg->header.size =
+    htons (sizeof (struct JoinNotificationMessage) + meta_len);
+  jnmsg->msg_options = p2p_jnmsg->msg_options;
+  jnmsg->public_key = new_entry->public_key;
+  memcpy (&jnmsg[1], &roomptr[room_name_len], meta_len);
+  entry = client_list_head;
+  while (NULL != entry)
+    {
+      if ((0 == strcmp (room_name, entry->room)) &&
+	  (NULL != entry->client))
+	{
+	  GNUNET_SERVER_notification_context_unicast (nc,
+						      entry->client,
+						      &jnmsg->header,
+						      GNUNET_NO);
+	}
+      entry = entry->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting join notification to neighbour peers\n");
+#endif
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_join_noficiation,
+			     new_entry);
+  GNUNET_free (jnmsg);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handle P2P leave notification.
+ *
+ * @param cls closure, always NULL
+ * @param other the other peer involved
+ * @param message the actual message
+ * @param atsi performance information
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_p2p_leave_notification (void *cls,
+			       const struct GNUNET_PeerIdentity *other,
+			       const struct GNUNET_MessageHeader *message,
+			       const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  const struct P2PLeaveNotificationMessage *p2p_lnmsg;
+  GNUNET_HashCode id;
+  struct ChatClient *pos;
+  struct ChatClient *prev;
+  struct ChatClient *entry;
+  struct LeaveNotificationMessage lnmsg;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Got P2P leave notification\n");
+  p2p_lnmsg = (const struct P2PLeaveNotificationMessage *) message;
+  GNUNET_CRYPTO_hash (&p2p_lnmsg->user,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      &id);
+  pos = client_list_head;
+  prev = NULL;
+  while (NULL != pos)
+    {
+      if (0 == memcmp (&pos->id, &id, sizeof (GNUNET_HashCode)))
+	break;
+      prev = pos;
+      pos = pos->next;
+    }
+  if (NULL == pos)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "No such client. There is nothing to do\n");
+#endif
+      return GNUNET_OK;
+    }
+  if (NULL == prev)
+    client_list_head = pos->next;
+  else
+    prev->next = pos->next;
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Notifying local room members that the client has gone away\n");
+#endif
+  lnmsg.header.size = htons (sizeof (struct LeaveNotificationMessage));
+  lnmsg.header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_LEAVE_NOTIFICATION);
+  lnmsg.reserved = htonl (0);
+  lnmsg.user = pos->public_key;
+  entry = client_list_head;
+  while (NULL != entry)
+    {
+      if (0 == strcmp (pos->room, entry->room) &&
+	  (NULL != entry->client))
+	{
+	  GNUNET_SERVER_notification_context_unicast (nc,
+						      entry->client,
+						      &lnmsg.header,
+						      GNUNET_NO);
+	}
+      entry = entry->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting leave notification to neighbour peers\n");
+#endif
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_leave_noficiation,
+			     pos);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handle P2P message notification.
+ *
+ * @param cls closure, always NULL
+ * @param other the other peer involved
+ * @param message the actual message
+ * @param atsi performance information
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_p2p_message_notification (void *cls,
+				 const struct GNUNET_PeerIdentity *other,
+				 const struct GNUNET_MessageHeader *message,
+				 const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  const struct P2PReceiveNotificationMessage *p2p_rnmsg;
+  struct P2PReceiveNotificationMessage *my_p2p_rnmsg;
+  struct ReceiveNotificationMessage *rnmsg;
+  struct ChatClient *sender;
+  struct ChatClient *pos;
+  static GNUNET_HashCode all_zeros;
+  int priv_msg;
+  uint16_t msg_len;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Got P2P message notification\n");
+  if (ntohs (message->size) <= sizeof (struct P2PReceiveNotificationMessage))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Malformed message: wrong size\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+  p2p_rnmsg = (const struct P2PReceiveNotificationMessage *) message;
+  sender = client_list_head;
+  while ((NULL != sender) &&
+	 (0 != memcmp (&sender->id,
+		       &p2p_rnmsg->sender,
+		       sizeof (GNUNET_HashCode))))
+    sender = sender->next;
+  if (NULL == sender)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Unknown source. Rejecting the message\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+  if (sender->msg_sequence_number >= ntohl (p2p_rnmsg->sequence_number))
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "This message has already been handled."
+		  " Sequence numbers (msg/sender): %u/%u\n",
+		  ntohl (p2p_rnmsg->sequence_number), sender->msg_sequence_number);
+#endif
+      return GNUNET_OK;
+    }
+  sender->msg_sequence_number = ntohl (p2p_rnmsg->sequence_number);
+  msg_len = ntohs (p2p_rnmsg->header.size) -
+    sizeof (struct P2PReceiveNotificationMessage);
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sending message to local room members\n");
+#endif
+  rnmsg = GNUNET_malloc (sizeof (struct ReceiveNotificationMessage) + msg_len);
+  rnmsg->header.size = htons (sizeof (struct ReceiveNotificationMessage) +
+			      msg_len);
+  rnmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_MESSAGE_NOTIFICATION);
+  rnmsg->msg_options = p2p_rnmsg->msg_options;
+  rnmsg->sequence_number = p2p_rnmsg->sequence_number;
+  priv_msg = (0 != memcmp (&all_zeros,
+			   &p2p_rnmsg->target, sizeof (GNUNET_HashCode)));
+  if (priv_msg)
+    memcpy (&rnmsg->encrypted_key,
+	    &p2p_rnmsg->encrypted_key,
+	    sizeof (struct GNUNET_CRYPTO_RsaEncryptedData));
+  memcpy (&rnmsg->sender, &p2p_rnmsg->sender, sizeof (GNUNET_HashCode));
+  memcpy (&rnmsg[1], &p2p_rnmsg[1], msg_len);
+  pos = client_list_head;
+  while (NULL != pos)
+    {
+      if ((0 == strcmp (sender->room, pos->room)) &&
+	  (NULL != pos->client))
+	{
+	  if (((!priv_msg) ||
+	       (0 == memcmp (&p2p_rnmsg->target,
+			     &pos->id,
+			     sizeof (GNUNET_HashCode)))) &&
+	      (0 == (ntohl (p2p_rnmsg->msg_options) & (~pos->msg_options))))
+	    {
+	      GNUNET_SERVER_notification_context_unicast (nc,
+							  pos->client,
+							  &rnmsg->header,
+							  GNUNET_NO);
+	    }
+	}
+      pos = pos->next;
+    }
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Broadcasting message notification to neighbour peers\n");
+#endif
+  my_p2p_rnmsg = GNUNET_memdup (p2p_rnmsg, ntohs (p2p_rnmsg->header.size));
+  GNUNET_CORE_iterate_peers (cfg,
+			     &send_message_noficiation,
+			     my_p2p_rnmsg);
+  GNUNET_free (rnmsg);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handle P2P sync request.
+ *
+ * @param cls closure, always NULL
+ * @param other the other peer involved
+ * @param message the actual message
+ * @param atsi performance information
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_p2p_sync_request (void *cls,
+			 const struct GNUNET_PeerIdentity *other,
+			 const struct GNUNET_MessageHeader *message,
+			 const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct ChatClient *entry;
+  struct GNUNET_CORE_TransmitHandle *th;
+  size_t msg_size;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Got P2P sync request\n");
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Notifying the requester of all known clients\n");
+#endif
+  entry = client_list_head;
+  while (NULL != entry)
+    {
+      msg_size = sizeof (struct P2PJoinNotificationMessage) +
+	strlen (entry->room) + 
+	entry->meta_len;
+      th = GNUNET_CORE_notify_transmit_ready (core,
+					      1,
+					      MAX_TRANSMIT_DELAY,
+					      other,
+					      msg_size,
+					      &transmit_join_notification_to_peer,
+					      entry);
+      GNUNET_assert (NULL != th);
+      entry = entry->next;
+    }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handle P2P confirmation receipt.
+ *
+ * @param cls closure, always NULL
+ * @param other the other peer involved
+ * @param message the actual message
+ * @param atsi performance information
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_p2p_confirmation_receipt (void *cls,
+				 const struct GNUNET_PeerIdentity *other,
+				 const struct GNUNET_MessageHeader *message,
+				 const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  const struct P2PConfirmationReceiptMessage *p2p_crmsg;
+  struct P2PConfirmationReceiptMessage *my_p2p_crmsg;
+  struct ConfirmationReceiptMessage *crmsg;
+  struct ChatClient *target;
+  struct ChatClient *author;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Got P2P confirmation receipt\n");
+  p2p_crmsg = (const struct P2PConfirmationReceiptMessage *) message;
+  target = client_list_head;
+  while ((NULL != target) &&
+	 (0 != memcmp (&target->id,
+		       &p2p_crmsg->target,
+		       sizeof (GNUNET_HashCode))))
+    target = target->next;
+  if (NULL == target)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Unknown source of the receipt. Rejecting the message\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+  if (target->rcpt_sequence_number >= ntohl (p2p_crmsg->sequence_number))
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "This receipt has already been handled."
+		  " Sequence numbers (msg/sender): %u/%u\n",
+		  ntohl (p2p_crmsg->sequence_number), target->rcpt_sequence_number);
+#endif
+      return GNUNET_OK;
+    }
+  target->rcpt_sequence_number = ntohl (p2p_crmsg->sequence_number);
+  author = client_list_head;
+  while ((NULL != author) &&
+	 (0 != memcmp (&author->id,
+		       &p2p_crmsg->author,
+		       sizeof (GNUNET_HashCode))))
+    author = author->next;
+  if (NULL == author)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		  "Unknown addressee. Rejecting the receipt\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+
+  if (NULL == author->client)
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "The author of the original message is not a local client."
+		  " Broadcasting receipt to neighbour peers\n");
+#endif
+      my_p2p_crmsg = GNUNET_memdup (p2p_crmsg, sizeof (struct P2PConfirmationReceiptMessage));
+      GNUNET_CORE_iterate_peers (cfg,
+				 &send_confirmation_receipt,
+				 my_p2p_crmsg);
+    }
+  else
+    {
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "The author of the original message is a local client."
+		  " Verifying signature of the receipt\n");
+#endif
+      crmsg = GNUNET_malloc (sizeof (struct ConfirmationReceiptMessage));
+      crmsg->header.size = htons (sizeof (struct ConfirmationReceiptMessage));
+      crmsg->header.type = htons (GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_NOTIFICATION);
+      crmsg->signature = p2p_crmsg->signature;
+      crmsg->purpose = p2p_crmsg->purpose;
+      crmsg->sequence_number = p2p_crmsg->msg_sequence_number;
+      crmsg->reserved2 = 0;
+      crmsg->timestamp = p2p_crmsg->timestamp;
+      crmsg->target = p2p_crmsg->target;
+      crmsg->author = p2p_crmsg->author;
+      crmsg->content = p2p_crmsg->content;
+      if (GNUNET_OK !=
+	  GNUNET_CRYPTO_rsa_verify (GNUNET_SIGNATURE_PURPOSE_CHAT_RECEIPT,
+				    &crmsg->purpose,
+				    &crmsg->signature,
+				    &target->public_key))
+	{
+	  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+		      "Invalid signature of the receipt\n");
+	  GNUNET_break_op (0);
+	  return GNUNET_SYSERR;
+	}
+#if DEBUG_CHAT_SERVICE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+		  "The author of the original message is a local client."
+		  " Sending receipt to the client\n");
+#endif
+      GNUNET_SERVER_notification_context_unicast (nc,
+						  author->client,
+						  &crmsg->header,
+						  GNUNET_NO);
+      GNUNET_free (crmsg);
+    }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Transmit a sync request to the peer.
+ *
+ * @param cls closure, NULL
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_sync_request_to_peer (void *cls,
+			       size_t size,
+			       void *buf)
+{
+  struct GNUNET_MessageHeader *m = buf;
+  size_t msg_size;
+
+#if DEBUG_CHAT_SERVICE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transmitting P2P sync request\n");
+#endif
+  msg_size = sizeof (struct GNUNET_MessageHeader);
+  GNUNET_assert (size >= msg_size);
+  GNUNET_assert (NULL != buf);
+  m = buf;
+  m->type = htons (GNUNET_MESSAGE_TYPE_CHAT_P2P_SYNC_REQUEST);
+  m->size = htons (msg_size);
+  return msg_size;
+}
+
+
+/**
+ * Method called whenever a peer connects.
+ *
+ * @param cls closure
+ * @param peer peer identity this notification is about
+ * @param atsi performance data
+ */
+static void 
+peer_connect_handler (void *cls,
+		      const struct GNUNET_PeerIdentity *peer,
+		      const struct GNUNET_TRANSPORT_ATS_Information *atsi)
+{
+  struct GNUNET_CORE_TransmitHandle *th;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+	      "Peer connected: %s\n", GNUNET_i2s (peer));
+  if (0 == memcmp (peer, me, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+  th = GNUNET_CORE_notify_transmit_ready (core,
+					  1,
+					  MAX_TRANSMIT_DELAY,
+					  peer,
+					  sizeof (struct GNUNET_MessageHeader),
+					  &transmit_sync_request_to_peer,
+					  NULL);
+  GNUNET_assert (NULL != th);
+}
+
+
+/**
+ * Method called whenever a peer disconnects.
+ *
+ * @param cls closure, not used
+ * @param peer peer identity this notification is about
+ */
+static void
+peer_disconnect_handler (void *cls,
+			 const struct GNUNET_PeerIdentity *peer)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+	      "Peer disconnected: %s\n", GNUNET_i2s (peer));
+}
+
+
+/**
+ * Task run during shutdown.
+ *
+ * @param cls unused
+ * @param tc unused
+ */
+static void
+cleanup_task (void *cls,
+	      const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Cleaning up\n");
+  if (NULL != core)
+    {
+      GNUNET_CORE_disconnect (core);
+      core = NULL;
+    }
+  if (NULL != nc)
+    {
+      GNUNET_SERVER_notification_context_destroy (nc);
+      nc = NULL;
+    }
+}
+
+
+/**
+ * To be called on core init/fail.
+ *
+ * @param cls closure, NULL
+ * @param server handle to the server for this service
+ * @param identity the public identity of this peer
+ * @param publicKey the public key of this peer
+ */
+static void
+core_init (void *cls,
+	   struct GNUNET_CORE_Handle *server,
+	   const struct GNUNET_PeerIdentity *my_identity,
+	   const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *publicKey)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Core initialized\n");
+  me = my_identity;
+}
+
+
+/**
+ * Process chat requests.
+ *
+ * @param cls closure, NULL
+ * @param server the initialized server
+ * @param cfg configuration to use
+ */
+static void
+run (void *cls,
+     struct GNUNET_SERVER_Handle *server,
+     const struct GNUNET_CONFIGURATION_Handle *c)
+{
+  static const struct GNUNET_SERVER_MessageHandler handlers[] =
+    {
+      { &handle_join_request, NULL,
+	GNUNET_MESSAGE_TYPE_CHAT_JOIN_REQUEST, 0 },
+      { &handle_transmit_request, NULL,
+	GNUNET_MESSAGE_TYPE_CHAT_TRANSMIT_REQUEST, 0 },
+      { &handle_acknowledge_request, NULL,
+	GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_RECEIPT,
+	sizeof (struct ConfirmationReceiptMessage) },
+      { NULL, NULL, 0, 0 }
+    };
+  static const struct GNUNET_CORE_MessageHandler p2p_handlers[] =
+    {
+      { &handle_p2p_join_notification,
+	GNUNET_MESSAGE_TYPE_CHAT_P2P_JOIN_NOTIFICATION, 0 },
+      { &handle_p2p_leave_notification,
+	GNUNET_MESSAGE_TYPE_CHAT_P2P_LEAVE_NOTIFICATION,
+	sizeof (struct P2PLeaveNotificationMessage) },
+      { &handle_p2p_message_notification,
+	GNUNET_MESSAGE_TYPE_CHAT_P2P_MESSAGE_NOTIFICATION, 0 },
+      { &handle_p2p_sync_request,
+	GNUNET_MESSAGE_TYPE_CHAT_P2P_SYNC_REQUEST,
+	sizeof (struct GNUNET_MessageHeader) },
+      { &handle_p2p_confirmation_receipt,
+	GNUNET_MESSAGE_TYPE_CHAT_P2P_CONFIRMATION_RECEIPT,
+	sizeof (struct P2PConfirmationReceiptMessage) },
+      { NULL, 0, 0 }
+    };
+
+  GNUNET_log_setup ("gnunet-service-chat",
+#if DEBUG_CHAT_SERVICE
+		    "DEBUG",
+#else
+		    "WARNING",
+#endif
+		    NULL);
+  cfg = c;
+  nc = GNUNET_SERVER_notification_context_create (server, 16);
+  GNUNET_SERVER_add_handlers (server, handlers);
+  core = GNUNET_CORE_connect (cfg,
+			      QUEUE_SIZE,
+			      NULL,
+			      &core_init,
+			      &peer_connect_handler,
+			      &peer_disconnect_handler,
+			      NULL,
+			      NULL, GNUNET_NO,
+			      NULL, GNUNET_NO,
+			      p2p_handlers);
+  GNUNET_SERVER_disconnect_notify (server, 
+				   &handle_client_disconnect,
+				   NULL);
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
+				&cleanup_task,
+				NULL);
+}
+
+
+/**
+ * The main function for the chat service.
+ *
+ * @param argc number of arguments from the command line
+ * @param argv command line arguments
+ * @return 0 ok, 1 on error
+ */
+int
+main (int argc, char *const *argv)
+{
+  return (GNUNET_OK ==
+	  GNUNET_SERVICE_run (argc,
+			      argv,
+			      "chat",
+			      GNUNET_SERVICE_OPTION_NONE,
+			      &run, NULL)) ? 0 : 1;
+}
+
+/* end of gnunet-service-chat.c */
Index: src/chat/gnunet-chat.c
===================================================================
--- src/chat/gnunet-chat.c	(revision 0)
+++ src/chat/gnunet-chat.c	(revision 0)
@@ -0,0 +1,674 @@
+/*
+     This file is part of GNUnet.
+     (C) 2007, 2008, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file chat/gnunet-chat.c
+ * @brief Minimal chat command line tool
+ * @author Christian Grothoff
+ * @author Nathan Evans
+ * @author Vitaly Minko
+ */
+
+#include "platform.h"
+#include "gnunet_getopt_lib.h"
+#include "gnunet_program_lib.h"
+#include "gnunet_chat_service.h"
+#include <fcntl.h>
+
+static int ret;
+
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+static char *nickname;
+
+static char *room_name;
+
+static struct GNUNET_CONTAINER_MetaData *meta;
+
+static struct GNUNET_CHAT_Room *room;
+
+static GNUNET_SCHEDULER_TaskIdentifier handle_cmd_task = GNUNET_SCHEDULER_NO_TASK;
+
+struct ChatCommand
+{
+  const char *command;
+  int (*Action) (const char *arguments, const void *xtra);
+  const char *helptext;
+};
+
+struct UserList
+{
+  struct UserList *next;
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded pkey;
+  int ignored;
+};
+
+static struct UserList *users;
+
+static void
+free_user_list ()
+{
+  struct UserList *next;
+  while (NULL != users)
+    {
+      next = users->next;
+      GNUNET_free (users);
+      users = next;
+    }
+}
+
+static int do_help (const char *args, const void *xtra);
+
+
+/**
+ * Callback used for notification about incoming messages.
+ *
+ * @param cls closure, NULL
+ * @param room in which room was the message received?
+ * @param sender what is the ID of the sender? (maybe NULL)
+ * @param member_info information about the joining member
+ * @param message the message text
+ * @param options options for the message
+ * @return GNUNET_OK to accept the message now, GNUNET_NO to
+ *         accept (but user is away), GNUNET_SYSERR to signal denied delivery
+ */
+static int
+receive_cb (void *cls,
+	    struct GNUNET_CHAT_Room *room,
+	    const GNUNET_HashCode *sender,
+	    const struct GNUNET_CONTAINER_MetaData *meta,
+	    const char *message,
+	    enum GNUNET_CHAT_MsgOptions options)
+{
+  char *nick;
+  const char *fmt;
+
+  if (NULL != sender)
+    nick = GNUNET_PSEUDONYM_id_to_name (cfg, sender);
+  else
+    nick = GNUNET_strdup (_("anonymous"));
+  fmt = NULL;
+  switch (options)
+    {
+    case GNUNET_CHAT_MSG_OPTION_NONE:
+    case GNUNET_CHAT_MSG_ANONYMOUS:
+      fmt = _("`%s' said: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_PRIVATE:
+      fmt = _("`%s' said to you: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ANONYMOUS:
+      fmt = _("`%s' said to you: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_AUTHENTICATED:
+      fmt = _("`%s' said for sure: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_AUTHENTICATED:
+      fmt = _("`%s' said to you for sure: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_ACKNOWLEDGED:
+      fmt = _("`%s' was confirmed that you received: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ACKNOWLEDGED:
+      fmt = _("`%s' was confirmed that you and only you received: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_AUTHENTICATED | GNUNET_CHAT_MSG_ACKNOWLEDGED:
+      fmt = _("`%s' was confirmed that you received from him or her: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_AUTHENTICATED | GNUNET_CHAT_MSG_PRIVATE | GNUNET_CHAT_MSG_ACKNOWLEDGED:
+      fmt =
+	_
+	("`%s' was confirmed that you and only you received from him or her: %s\n");
+      break;
+    case GNUNET_CHAT_MSG_OFF_THE_RECORD:
+      fmt = _("`%s' said off the record: %s\n");
+      break;
+    default:
+      fmt = _("<%s> said using an unknown message type: %s\n");
+      break;
+    }
+  fprintf (stdout, fmt, nick, message);
+  GNUNET_free (nick);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Callback used for message delivery confirmations.
+ *
+ * @param cls closure, NULL
+ * @param room in which room was the message received?
+ * @param orig_seq_number sequence number of the original message
+ * @param timestamp when was the message received?
+ * @param receiver who is confirming the receipt?
+ * @param msg_hash hash of the original message
+ * @param receipt signature confirming delivery
+ * @return GNUNET_OK to continue, GNUNET_SYSERR to refuse processing further
+ *         confirmations from anyone for this message
+ */
+static int
+confirmation_cb (void *cls,
+		 struct GNUNET_CHAT_Room *room,
+		 uint32_t orig_seq_number,
+		 struct GNUNET_TIME_Absolute timestamp,
+		 const GNUNET_HashCode *receiver,
+		 const GNUNET_HashCode *msg_hash,
+		 const struct GNUNET_CRYPTO_RsaSignature *receipt)
+{
+  char *nick;
+
+  nick = GNUNET_PSEUDONYM_id_to_name (cfg, receiver);
+  fprintf (stdout, _("'%s' acknowledged message #%d\n"), nick, orig_seq_number);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Callback used for notification that another room member has joined or left.
+ *
+ * @param member_info will be non-null if the member is joining, NULL if he is
+ *        leaving
+ * @param member_id hash of public key of the user (for unique identification)
+ * @param options what types of messages is this member willing to receive?
+ * @return GNUNET_OK
+ */
+static int
+member_list_cb (void *cls,
+		const struct GNUNET_CONTAINER_MetaData *member_info,
+		const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *member_id,
+		enum GNUNET_CHAT_MsgOptions options)
+{
+  char *nick;
+  GNUNET_HashCode id;
+  struct UserList *pos;
+  struct UserList *prev;
+
+  GNUNET_CRYPTO_hash (member_id,
+		      sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+		      &id);
+  nick = GNUNET_PSEUDONYM_id_to_name (cfg, &id);
+  fprintf (stdout, member_info != NULL
+	   ? _("`%s' entered the room\n") : _("`%s' left the room\n"), nick);
+  GNUNET_free (nick);
+  if (NULL != member_info)
+    {
+      /* user joining */
+      pos = GNUNET_malloc (sizeof (struct UserList));
+      pos->next = users;
+      pos->pkey = *member_id;
+      pos->ignored = GNUNET_NO;
+      users = pos;
+    }
+  else
+    {
+      /* user leaving */
+      prev = NULL;
+      pos = users;
+      while ((NULL != pos) &&
+	     (0 != memcmp (&pos->pkey,
+			   member_id,
+			   sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded))))
+	{
+	  prev = pos;
+	  pos = pos->next;
+	}
+      if (NULL == pos)
+	{
+	  GNUNET_break (0);
+	}
+      else
+	{
+	  if (NULL == prev)
+	    users = pos->next;
+	  else
+	    prev->next = pos->next;
+	  GNUNET_free (pos);
+	}
+    }
+  return GNUNET_OK;
+}
+
+
+static int
+do_transmit (const char *msg, const void *xtra)
+{
+  uint32_t seq;
+  GNUNET_CHAT_send_message (room,
+			    msg,
+			    GNUNET_CHAT_MSG_OPTION_NONE,
+			    NULL, &seq);
+  return GNUNET_OK;
+}
+
+
+static int
+do_join (const char *arg, const void *xtra)
+{
+  char *my_name;
+  GNUNET_HashCode me;
+
+  if (arg[0] == '#')
+    arg++;                      /* ignore first hash */
+  GNUNET_CHAT_leave_room (room);
+  free_user_list ();
+  GNUNET_free (room_name);
+  room_name = GNUNET_strdup (arg);
+  room = GNUNET_CHAT_join_room (cfg,
+				nickname,
+				meta,
+				room_name,
+				-1,
+				&receive_cb, NULL,
+				&member_list_cb, NULL,
+				&confirmation_cb, NULL, &me);
+  if (NULL == room)
+    {
+      fprintf (stdout, _("Could not change username\n"));
+      return GNUNET_SYSERR;
+    }
+  my_name = GNUNET_PSEUDONYM_id_to_name (cfg, &me);
+  fprintf (stdout, _("Joined room `%s' as user `%s'\n"), room_name, my_name);
+  GNUNET_free (my_name);
+  return GNUNET_OK;
+}
+
+
+static int
+do_nick (const char *msg, const void *xtra)
+{
+  char *my_name;
+  GNUNET_HashCode me;
+
+  GNUNET_CHAT_leave_room (room);
+  free_user_list ();
+  GNUNET_free (nickname);
+  GNUNET_CONTAINER_meta_data_destroy (meta);
+  nickname = GNUNET_strdup (msg);
+  meta = GNUNET_CONTAINER_meta_data_create ();
+  GNUNET_CONTAINER_meta_data_insert (meta,
+				     "<gnunet>",
+				     EXTRACTOR_METATYPE_TITLE,
+				     EXTRACTOR_METAFORMAT_UTF8,
+				     "text/plain",
+				     nickname,
+				     strlen(nickname)+1);
+  room = GNUNET_CHAT_join_room (cfg,
+				nickname,
+				meta,
+				room_name,
+				-1,
+				&receive_cb, NULL,
+				&member_list_cb, NULL,
+				&confirmation_cb, NULL, &me);
+  if (NULL == room)
+    {
+      fprintf (stdout, _("Could not change username\n"));
+      return GNUNET_SYSERR;
+    }
+  my_name = GNUNET_PSEUDONYM_id_to_name (cfg, &me);
+  fprintf (stdout, _("Changed username to `%s'\n"), my_name);
+  GNUNET_free (my_name);
+  return GNUNET_OK;
+}
+
+
+static int
+do_names (const char *msg, const void *xtra)
+{
+  char *name;
+  struct UserList *pos;
+  GNUNET_HashCode pid;
+
+  fprintf (stdout, _("Users in room `%s': "), room_name);
+  pos = users;
+  while (NULL != pos)
+    {
+      GNUNET_CRYPTO_hash (&pos->pkey,
+			  sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+			  &pid);
+      name = GNUNET_PSEUDONYM_id_to_name (cfg, &pid);
+      fprintf (stdout, "`%s' ", name);
+      GNUNET_free (name);
+      pos = pos->next;
+    }
+  fprintf (stdout, "\n");
+  return GNUNET_OK;
+}
+
+
+static int
+do_pm (const char *msg, const void *xtra)
+{
+  char *user;
+  GNUNET_HashCode uid;
+  GNUNET_HashCode pid;
+  uint32_t seq;
+  struct UserList *pos;
+
+  if (NULL == strstr (msg, " "))
+    {
+      fprintf (stderr, _("Syntax: /msg USERNAME MESSAGE"));
+      return GNUNET_OK;
+    }
+  user = GNUNET_strdup (msg);
+  strstr (user, " ")[0] = '\0';
+  msg += strlen (user) + 1;
+  if (GNUNET_OK != GNUNET_PSEUDONYM_name_to_id (cfg, user, &uid))
+    {
+      fprintf (stderr, _("Unknown user `%s'\n"), user);
+      GNUNET_free (user);
+      return GNUNET_OK;
+    }
+  pos = users;
+  while (NULL != pos)
+    {
+      GNUNET_CRYPTO_hash (&pos->pkey,
+			  sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+			  &pid);
+      if (0 == memcmp (&pid, &uid, sizeof (GNUNET_HashCode)))
+	break;
+      pos = pos->next;
+    }
+  if (NULL == pos)
+    {
+      fprintf (stderr, _("User `%s' is currently not in the room!\n"), user);
+      GNUNET_free (user);
+      return GNUNET_OK;
+    }
+  GNUNET_CHAT_send_message (room,
+			    msg,
+			    GNUNET_CHAT_MSG_PRIVATE,
+			    &pos->pkey,
+			    &seq);
+  GNUNET_free (user);
+  return GNUNET_OK;
+}
+
+
+static int
+do_transmit_sig (const char *msg, const void *xtra)
+{
+  uint32_t seq;
+  GNUNET_CHAT_send_message (room,
+			    msg,
+			    GNUNET_CHAT_MSG_AUTHENTICATED,
+			    NULL, &seq);
+  return GNUNET_OK;
+}
+
+
+static int
+do_transmit_ack (const char *msg, const void *xtra)
+{
+  uint32_t seq;
+  GNUNET_CHAT_send_message (room,
+			    msg,
+			    GNUNET_CHAT_MSG_ACKNOWLEDGED,
+			    NULL, &seq);
+  return GNUNET_OK;
+}
+
+
+static int
+do_quit (const char *args, const void *xtra)
+{
+  return GNUNET_SYSERR;
+}
+
+
+static int
+do_unknown (const char *msg, const void *xtra)
+{
+  fprintf (stderr, _("Unknown command `%s'\n"), msg);
+  return GNUNET_OK;
+}
+
+
+/**
+ * List of supported IRC commands. The order matters!
+ */
+static struct ChatCommand commands[] = {
+  {"/join ", &do_join,
+   gettext_noop
+   ("Use `/join #roomname' to join a chat room. Joining a room will cause you"
+    " to leave the current room")},
+  {"/nick ", &do_nick,
+   gettext_noop
+   ("Use `/nick nickname' to change your nickname.  This will cause you to"
+    " leave the current room and immediately rejoin it with the new name.")},
+  {"/msg ", &do_pm,
+   gettext_noop
+   ("Use `/msg nickname message' to send a private message to the specified"
+    " user")},
+  {"/notice ", &do_pm,
+   gettext_noop ("The `/notice' command is an alias for `/msg'")},
+  {"/query ", &do_pm,
+   gettext_noop ("The `/query' command is an alias for `/msg'")},
+  {"/sig ", &do_transmit_sig,
+   gettext_noop ("Use `/sig message' to send a signed public message")},
+  {"/ack ", &do_transmit_ack,
+   gettext_noop
+   ("Use `/ack message' to require signed acknowledgment of the message")},
+  {"/quit", &do_quit,
+   gettext_noop ("Use `/quit' to terminate gnunet-chat")},
+  {"/leave", &do_quit,
+   gettext_noop ("The `/leave' command is an alias for `/quit'")},
+  {"/names", &do_names,
+   gettext_noop
+   ("Use `/names' to list all of the current members in the chat room")},
+  {"/help", &do_help,
+   gettext_noop ("Use `/help command' to get help for a specific command")},
+  /* Add standard commands:
+     /whois (print metadata),
+     /ignore (set flag, check on receive!) */
+  /* Add special commands (currently supported):
+     + anonymous msgs
+     + authenticated msgs
+   */
+  /* the following three commands must be last! */
+  {"/", &do_unknown, NULL},
+  {"", &do_transmit, NULL},
+  {NULL, NULL, NULL},
+};
+
+
+static int
+do_help (const char *args, const void *xtra)
+{
+  int i;
+  i = 0;
+  while ((NULL != args) &&
+	 (0 != strlen (args)) && (commands[i].Action != &do_help))
+    {
+      if (0 ==
+	  strncasecmp (&args[1], &commands[i].command[1], strlen (args) - 1))
+	{
+	  fprintf (stdout, "%s\n", gettext (commands[i].helptext));
+	  return GNUNET_OK;
+	}
+      i++;
+    }
+  i = 0;
+  fprintf (stdout, "Available commands:");
+  while (commands[i].Action != &do_help)
+    {
+      fprintf (stdout, " %s", gettext (commands[i].command));
+      i++;
+    }
+  fprintf (stdout, "\n");
+  fprintf (stdout, "%s\n", gettext (commands[i].helptext));
+  return GNUNET_OK;
+}
+
+
+static void 
+do_stop_task (void *cls,
+	      const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  GNUNET_CHAT_leave_room (room);
+  if (handle_cmd_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (handle_cmd_task);
+      handle_cmd_task = GNUNET_SCHEDULER_NO_TASK;
+    }     
+  free_user_list ();
+  GNUNET_CONTAINER_meta_data_destroy (meta);
+  GNUNET_free (room_name);
+  GNUNET_free (nickname);
+}
+
+
+void
+handle_command (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  char message[MAX_MESSAGE_LENGTH + 1];
+  int i;
+
+  /* read message from command line and handle it */
+  memset (message, 0, MAX_MESSAGE_LENGTH + 1);
+  if (NULL == fgets (message, MAX_MESSAGE_LENGTH, stdin))
+    goto next;
+  if (strlen (message) == 0)
+    goto next;
+  if (message[strlen (message) - 1] == '\n')
+    message[strlen (message) - 1] = '\0';
+  if (strlen (message) == 0)
+    goto next;
+  i = 0;
+  while ((NULL != commands[i].command) &&
+	 (0 != strncasecmp (commands[i].command,
+			    message, strlen (commands[i].command))))
+    i++;
+  if (GNUNET_OK !=
+      commands[i].Action (&message[strlen (commands[i].command)], NULL))
+    goto out;
+
+next:
+  handle_cmd_task =
+    GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS,
+								 100),
+				  &handle_command,
+				  NULL);
+  return;
+
+out:
+  handle_cmd_task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_SCHEDULER_shutdown ();
+}
+
+
+/**
+ * Main function that will be run by the scheduler.
+ *
+ * @param cls closure, NULL
+ * @param args remaining command-line arguments
+ * @param cfgfile name of the configuration file used (for saving, can be NULL!)
+ * @param cfg configuration
+ */
+static void
+run (void *cls,
+     char *const *args,
+     const char *cfgfile,
+     const struct GNUNET_CONFIGURATION_Handle *c)
+{
+  GNUNET_HashCode me;
+  char *my_name;
+
+  cfg = c;
+  /* check arguments */
+  if (NULL == nickname)
+    {
+      fprintf (stderr, _("You must specify a nickname\n"));
+      ret = -1;
+      return;
+    }
+  if (NULL == room_name)
+    room_name = GNUNET_strdup ("gnunet");
+  meta = GNUNET_CONTAINER_meta_data_create ();
+  GNUNET_CONTAINER_meta_data_insert (meta,
+				     "<gnunet>",
+				     EXTRACTOR_METATYPE_TITLE,
+				     EXTRACTOR_METAFORMAT_UTF8,
+				     "text/plain",
+				     nickname,
+				     strlen(nickname)+1);
+  room = GNUNET_CHAT_join_room (cfg,
+				nickname,
+				meta,
+				room_name,
+				-1,
+				&receive_cb, NULL,
+				&member_list_cb, NULL,
+				&confirmation_cb, NULL, &me);
+  if (NULL == room)
+    {
+      fprintf (stderr, _("Failed to join room `%s'\n"), room_name);
+      GNUNET_free (room_name);
+      GNUNET_free (nickname);
+      GNUNET_CONTAINER_meta_data_destroy (meta);
+      ret = -1;
+      return;
+    }
+  my_name = GNUNET_PSEUDONYM_id_to_name (cfg, &me);
+  fprintf (stdout, _("Joined room `%s' as user `%s'\n"), room_name, my_name);
+  GNUNET_free (my_name);
+  handle_cmd_task =
+    GNUNET_SCHEDULER_add_with_priority (GNUNET_SCHEDULER_PRIORITY_UI,
+					&handle_command,
+					NULL);
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
+				&do_stop_task,
+				NULL);
+}
+
+
+/**
+ * The main function to chat via GNUnet.
+ *
+ * @param argc number of arguments from the command line
+ * @param argv command line arguments
+ * @return 0 ok, 1 on error
+ */
+int
+main (int argc, char *const *argv)
+{
+  int flags;
+  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
+    {'n', "nick", "NAME",
+     gettext_noop ("set the nickname to use (required)"),
+     1, &GNUNET_GETOPT_set_string, &nickname},
+    {'r', "room", "NAME",
+     gettext_noop ("set the chat room to join"),
+     1, &GNUNET_GETOPT_set_string, &room_name},
+    GNUNET_GETOPT_OPTION_END
+  };
+
+  flags = fcntl (0, F_GETFL, 0);
+  flags |= O_NONBLOCK;
+  fcntl (0, F_SETFL, flags);
+  return (GNUNET_OK ==
+	  GNUNET_PROGRAM_run (argc,
+			      argv,
+			      "gnunet-chat",
+			      gettext_noop ("Join a chat on GNUnet."),
+			      options, &run, NULL)) ? ret : 1;
+}
+
+/* end of gnunet-chat.c */
Index: src/include/gnunet_protocols.h
===================================================================
--- src/include/gnunet_protocols.h	(revision 14186)
+++ src/include/gnunet_protocols.h	(working copy)
@@ -738,13 +738,79 @@
 
 
 /**
+ * Message sent from client to join a chat room.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_JOIN_REQUEST 300
+
+/**
+ * Message sent to client to indicate joining of another room member.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_JOIN_NOTIFICATION 301
+
+/**
+ * Message sent to client to indicate leaving of another room member.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_LEAVE_NOTIFICATION 302
+
+/**
+ * Notification sent by service to client indicating that we've received a chat
+ * message.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_MESSAGE_NOTIFICATION 303
+
+/**
+ * Request sent by client to transmit a chat message to another room members.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_TRANSMIT_REQUEST 304
+
+/**
+ * Receipt sent from a message receiver to the service to confirm delivery of
+ * a chat message.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_RECEIPT 305
+
+/**
+ * Notification sent from the service to the original sender
+ * to acknowledge delivery of a chat message.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_CONFIRMATION_NOTIFICATION 306
+
+/**
+ * P2P message sent to indicate joining of another room member.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_P2P_JOIN_NOTIFICATION 307
+
+/**
+ * P2P message sent to indicate leaving of another room member.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_P2P_LEAVE_NOTIFICATION 308
+
+/**
+ * P2P message sent to a newly connected peer to request its known clients in
+ * order to synchronize room members.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_P2P_SYNC_REQUEST 309
+
+/**
+ * Notification sent from one peer to another to indicate that we have received
+ * a chat message.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_P2P_MESSAGE_NOTIFICATION 310
+
+/**
+ * P2P receipt confirming delivery of a chat message.
+ */
+#define GNUNET_MESSAGE_TYPE_CHAT_P2P_CONFIRMATION_RECEIPT 311
+
+
+/**
  * Type used to match 'all' message types.
  */
 #define GNUNET_MESSAGE_TYPE_ALL 65535
 
 /*
   TODO:
-  - applications (FS, VPN, CHAT, TRACEKIT, TBENCH)
+  - applications (FS, VPN, TRACEKIT, TBENCH)
 */
 
 
Index: src/include/gnunet_chat_service.h
===================================================================
--- src/include/gnunet_chat_service.h	(revision 0)
+++ src/include/gnunet_chat_service.h	(revision 0)
@@ -0,0 +1,234 @@
+/*
+     This file is part of GNUnet.
+     (C) 2009, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file include/gnunet_chat_service.h
+ * @brief API for chatting via GNUnet 
+ * @author Christian Grothoff
+ * @author Nathan Evans
+ * @author Vitaly Minko
+ */
+
+#ifndef GNUNET_CHAT_SERVICE_H
+#define GNUNET_CHAT_SERVICE_H
+
+#include "gnunet_util_lib.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+#define GNUNET_CHAT_VERSION 0x00000003
+#define MAX_MESSAGE_LENGTH (32 * 1024)
+
+/**
+ * Options for messaging.  Compatible options can be OR'ed together.
+ */
+enum GNUNET_CHAT_MsgOptions
+  {
+    /**
+     * No special options.
+     */
+    GNUNET_CHAT_MSG_OPTION_NONE = 0,
+  
+    /**
+     * Encrypt the message so that only the receiver can decrypt it.
+     */
+    GNUNET_CHAT_MSG_PRIVATE = 1,
+  
+    /**
+     * Hide the identity of the sender.
+     */
+    GNUNET_CHAT_MSG_ANONYMOUS = 2,
+  
+    /**
+     * Sign the content, authenticating the sender (using the provided private
+     * key, which may represent a pseudonym).
+     */
+    GNUNET_CHAT_MSG_AUTHENTICATED = 4,
+  
+    /**
+     * Require signed acknowledgment before completing delivery (and of course,
+     * only acknowledge if delivery is guaranteed).
+     */
+    GNUNET_CHAT_MSG_ACKNOWLEDGED = 8,
+  
+    /**
+     * Authenticate for the receiver, but ensure that receiver cannot prove
+     * authenticity to third parties later. (not yet implemented)
+     */
+    GNUNET_CHAT_MSG_OFF_THE_RECORD = 16,
+  
+  };
+
+/**
+ * Handle for a (joined) chat room.
+ */
+struct GNUNET_CHAT_Room;
+
+/**
+ * Callback used for notification about incoming messages.
+ *
+ * @param cls closure
+ * @param room in which room was the message received?
+ * @param sender what is the ID of the sender? (maybe NULL)
+ * @param member_info information about the joining member
+ * @param message the message text
+ * @param options options for the message
+ * @return GNUNET_OK to accept the message now, GNUNET_NO to
+ *         accept (but user is away), GNUNET_SYSERR to signal denied delivery
+ */
+typedef int (*GNUNET_CHAT_MessageCallback) (void *cls,
+					    struct GNUNET_CHAT_Room *room,
+					    const GNUNET_HashCode *sender,
+					    const struct GNUNET_CONTAINER_MetaData *member_info,
+					    const char *message,
+					    enum GNUNET_CHAT_MsgOptions options);
+
+/**
+ * Callback used for notification that another room member has joined or left.
+ *
+ * @param member_info will be non-null if the member is joining, NULL if he is
+ *        leaving
+ * @param member_id hash of public key of the user (for unique identification)
+ * @param options what types of messages is this member willing to receive?
+ * @return GNUNET_OK
+ */
+typedef int (*GNUNET_CHAT_MemberListCallback) (void *cls,
+					       const struct GNUNET_CONTAINER_MetaData *member_info,
+					       const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *member_id,
+					       enum GNUNET_CHAT_MsgOptions options);
+
+/**
+ * Callback used for message delivery confirmations.
+ *
+ * @param cls closure
+ * @param room in which room was the message received?
+ * @param orig_seq_number sequence number of the original message
+ * @param timestamp when was the message received?
+ * @param receiver who is confirming the receipt?
+ * @param msg_hash hash of the original message
+ * @param receipt signature confirming delivery
+ * @return GNUNET_OK to continue, GNUNET_SYSERR to refuse processing further
+ *         confirmations from anyone for this message
+ */
+typedef int (*GNUNET_CHAT_MessageConfirmation) (void *cls,
+						struct GNUNET_CHAT_Room *room,
+						uint32_t orig_seq_number,
+						struct GNUNET_TIME_Absolute timestamp,
+						const GNUNET_HashCode *receiver,
+						const GNUNET_HashCode *msg_hash,
+						const struct GNUNET_CRYPTO_RsaSignature *receipt);
+
+/**
+ * Join a chat room.
+ *
+ * @param cfg configuration
+ * @param nick_name nickname of the user joining (used to
+ *                  determine which public key to use);
+ *                  the nickname should probably also
+ *                  be used in the member_info (as "EXTRACTOR_TITLE")
+ * @param member_info information about the joining member
+ * @param room_name name of the room
+ * @param msg_options message options of the joining user
+ * @param messageCallback which function to call if a message has
+ *        been received?
+ * @param message_cls argument to callback
+ * @param memberCallback which function to call for join/leave notifications
+ * @param member_cls argument to callback
+ * @param confirmationCallback which function to call for confirmations
+ *        (maybe NULL)
+ * @param confirmation_cls argument to callback
+ * @param me member ID (pseudonym)
+ * @return NULL on error
+ */
+struct GNUNET_CHAT_Room *
+GNUNET_CHAT_join_room (const struct GNUNET_CONFIGURATION_Handle *cfg,
+		       const char *nick_name,
+		       struct GNUNET_CONTAINER_MetaData *member_info,
+		       const char *room_name,
+		       enum GNUNET_CHAT_MsgOptions msg_options,
+		       GNUNET_CHAT_MessageCallback messageCallback,
+		       void *message_cls,
+		       GNUNET_CHAT_MemberListCallback memberCallback,
+		       void *member_cls,
+		       GNUNET_CHAT_MessageConfirmation confirmationCallback,
+		       void *confirmation_cls,
+		       GNUNET_HashCode *me);
+
+/**
+ * Send a message.
+ *
+ * @param room handle for the chat room
+ * @param message message to be sent
+ * @param options options for the message
+ * @param receiver use NULL to send to everyone in the room
+ * @param sequence_number where to write the sequence id of the message
+ */
+void
+GNUNET_CHAT_send_message (struct GNUNET_CHAT_Room *room,
+			  const char *message,
+			  enum GNUNET_CHAT_MsgOptions options,
+			  const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *receiver,
+			  uint32_t *sequence_number);
+
+
+/**
+ * Leave a chat room.
+ */
+void
+GNUNET_CHAT_leave_room (struct GNUNET_CHAT_Room *chat_room);
+
+
+#if 0
+/* these are not yet implemented / supported */
+/**
+ * Callback function to iterate over rooms.
+ *
+ * @return GNUNET_OK to continue, GNUNET_SYSERR to abort iteration
+ */
+typedef int (*GNUNET_CHAT_RoomIterator) (const char *room,
+                                         const char *topic, void *cls);
+
+/**
+ * List all of the (publically visible) chat rooms.
+ * @return number of rooms on success, GNUNET_SYSERR if iterator aborted
+ */
+int GNUNET_CHAT_list_rooms (struct GNUNET_GE_Context *ectx,
+                            struct GNUNET_GC_Configuration *cfg,
+                            GNUNET_CHAT_RoomIterator it, void *cls);
+#endif
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+/* end of gnunet_chat_service.h */
Index: src/include/gnunet_signatures.h
===================================================================
--- src/include/gnunet_signatures.h	(revision 14186)
+++ src/include/gnunet_signatures.h	(working copy)
@@ -102,6 +102,15 @@
  */
 #define GNUNET_SIGNATURE_PURPOSE_DNS_RECORD 11
 
+/**
+ * Signature of a chat message.
+ */
+#define GNUNET_SIGNATURE_PURPOSE_CHAT_MESSAGE 12
+
+/**
+ * Signature of confirmation receipt for a chat message.
+ */
+#define GNUNET_SIGNATURE_PURPOSE_CHAT_RECEIPT 13
 
 #if 0                           /* keep Emacsens' auto-indent happy */
 {
Index: src/Makefile.am
===================================================================
--- src/Makefile.am	(revision 14186)
+++ src/Makefile.am	(working copy)
@@ -32,4 +32,5 @@
   fs \
   fragmentation \
   mesh \
-  vpn
+  vpn \
+  chat
Index: configure.ac
===================================================================
--- configure.ac	(revision 14186)
+++ configure.ac	(working copy)
@@ -810,6 +810,7 @@
 src/transport/Makefile
 src/util/Makefile
 src/vpn/Makefile
+src/chat/Makefile
 pkgconfig/Makefile
 pkgconfig/gnunetarm.pc
 pkgconfig/gnunetblock.pc