The XMPP (Jabber) component supports any number of XEP/JEP's through the SendCommand method, which you can use to send any command you like. This can be used to implement group chat (aka multi-user chat), for example:

To join a room:

xmpp.SendCommand("\n0\n");

To send a message to the room:

xmpp.MessageText = "Hello room!";
xmpp.MessageType = XmppMessageTypes.mtGroupChat;
xmpp.SendMessage("chatroom@conference.server");

To exit a room:

xmpp.SendCommand("");