Multiple messages in one SOAPCall

Is it possible to do multiple calls to SOAPCall.encode(...) to send
multiple messages over the same connection? If not, is there another
way to achieve the same result?

A client/server application we have uses SOAP for its operations and it
has keepalive enabled to allow us to send multiple operations over the
same TCP socket and avoid reoccuring TCP connection handshaking. Since
we have done that, we have also started to maintain "session"
information on the server for some operation sequences. Our application
can require bursts of hundreds of operations    for about one second.

We are implementing a mozilla based "light" version of the client but
need to find a way for the "session" nature of the information to
survive.

We would like to avoid redesigning the soap messages to encapsulate the
multiple existing operations into a single operation.

Thanks,

Marc