I have establish chat communication between two users using jabber-net xmpp client and vysper server by apache.
I am looking for broadcast facility using the same.
There are different mechanisms for "broadcasting", a word which I understand as "sending one message which is distributed by the server to many receivers".
When a user changes his "status" (for example "do not disturb me - I'm coding") a so call "presence" message is sent out which is distributed to all his contacts. This is a broadcast, and presence messages are intended to do that in XMPP.
There is at least another popular possibility: multi-user chat ("MUC"). MUC has the notion of "rooms", where users can "enter" to become part of a "conversation". Every message sent by one of the participants is sent to all others.
There are more similar mechanisms available, depending on what you actually want to do.