The Instant Messaging (IM) model assumes that a client maintains a separate window for each "peer", where a "peer" is some other IM user taking part in an IM conversation.
This operation sends an Instant Message to the specified user. The Server sends a XIMSS response without waiting till the Instant Message is actually delivered (or failed).
There is no explicit IM session opening operation. If the Server does not have an open IM session with the specified peer, a new session is created.
The Server sends the following data messages:
These asynchronous data messages are sent when the Server receives an Instant Message for the client user.
There is no explicit Instant Message session opening operation. If the client has no open conversation window for the specified user, it should open a new one.