+Sending messages back and forth is at the core of instant messaging. Two classes +aid in sending and recieiving messages: +
+Chat +
+ +A chat creates a new thread of messgaes (using a thread ID) between two users. The +following code snippet demonstrates how to create a new Chat with a user and then send +them a text message:+ +
+// Assume we've created an XMPPConnection name "connection".
+Chat newChat = connection.createChat("jsmith@jivesoftware.com");
+newChat.sendMessage("Howdy!");
++ +The Chat.sendMessage(String) method is a convenience method that creates a Message +object, sets the body using the String parameter, then sends the message. In the case +that you wish to set additional values on a Message before sending it, use the +Chat.createMessage() and Chat.sendMessage(Message) methods, as in the +following code snippet:
+ +
+// Assume we've created an XMPPConnection name "connection".
+Chat newChat = connection.createChat("jsmith@jivesoftware.com");
+Message newMessage = newChat.createMessage();
+newMessage.setBody("Howdy!");
+message.setProperty("favoriteColor", "red");
+newChat.sendMessage(newMessage);
++ +The Chat object allows you to easily listen for replies from the other chat participant. +The following code snippet is a parrot-bot -- it echoes back everything the other user types.
+ +
+// Assume we've created an XMPPConnection name "connection".
+Chat newChat = connection.createChat("jsmith@jivesoftware.com");
+newMessage.setBody("Hi, I'm an annoying parrot-bot! Type something back to me.");
+while (true) {
+ // Wait for the next message the user types to us.
+ Message message = newChat.nextMessage();
+ // Send back the same text the other user sent us.
+ newChat.sendMessage(message.getBody());
+}
++ +The code above uses the Chat.nextMessage() method to get the next message, which +will wait indefinitely until another message comes in. There are other methods to wait +a specific amount of time for a new message, or you can add a listener that will be notified +every time a new message arrives. + +
+GroupChat +
+ +A group chat connects to a chat room on a server and allows you to send and receive messages +from a group of people. Before you can send or receive messages, you must join the room using +a nickname. The following code snippet connects to a chat room and sends a +message.+ +
+// Assume we've created an XMPPConnection name "connection".
+GroupChat newGroupChat = connection.createGroupChat("test@jivesoftware.com");
+// Join the gropu chat using the nickname "jsmith".
+newGroupChat.join("jsmith");
+// Send a message to all the other people in the chat room.
+newGroupChat.sendMessage("Howdy!");
++ +In general, sending and receiving messages in a group chat works very similarly to +the Chat class. Method are also provided to get the list of the other +users in the room.
+
+
+
+
-Smack is a library for communicating with XMPP (Jabber) servers to perform -instant messaging and chat. +Smack is a library for communicating with XMPP servers to perform +instant messaging and chat.
-Key Advantages: +Smack Key Advantages
+About XMPP +
+ +XMPP (eXtensible Messaging and Presence Protocol) is an open, XML based protocol +making it's way through the IETF approval process under the guidance of the +Jabber Software Foundation (http://www.jabber.org). +For a good overview of the protocol, read the first chapter of Instant Messaging +in Java, available free at +http://www.jivesoftware.com/products/messenger/book/ + ++ +Smack provides a flexible framework for processing incoming packets using two constructs: +
+ +The org.jivesoftware.smack.filter.PacketFilter interface determines which +specific packets will be delivered to a PacketCollector or PacketListener. +Many pre-defined filters can be found in the org.jivesoftware.smack.filter package. + +
+The following code snippet demonstrates registering both a packet collector and a packet +listener:
+ +
+// Create a packet filter to listen for new messages from a particular
+// user. We use an AndFilter to combine two other filters.
+PacketFilter filter = new AndFilter(new PacketTypeTypeFilter(Message.class),
+ new FromContainsFilter("mary@jivesoftware.com"));
+// Assume we've created an XMPPConnection name "connection".
+
+// First, register a packet collector using the filter we created.
+PacketCollector myCollector = connection.createPacketCollector(filter);
+// Normally, you'd do something with the collector, like wait for new packets.
+
+// Next, create a packet listener. We use an anonymous inner class for brevity.
+PacketListener myListener = new PacketListener() {
+ public void processPacket(Packet packet) {
+ // Do something with the incoming packet here.
+ }
+ };
+// Register the listener.
+connection.addPacketListener(myListener, filter);
++ +
+Standard Packet Filters +
+ +A rich set of packet filters are included with Smack, or you can create your own filters by coding +to the PacketFilter interface. The default set of filters includes: +