Handling REFER with Replaces Requests

Sending REFER with Replaces

Use the InviteSession::refer(referTo, sessionToReplace) API - this will cause a REFER message to be sent to the other party that contains a Replaces header specifying the session to replace.

Receiving REFER with Replaces

For an application standpoint, this is handled in the exact same manner as receiving a REFER request without a Replaces header. If an application wishes to process the REFER request it should use the dum->makeInviteSessionFromRefer API.

Sample Code:

void onRefer(InviteSessionHandle is, ServerSubscriptionHandle ss, const SipMessage& msg)
{
   ss->send(ss->accept(202));  // accept refer request
   SdpContents sdpOffer;
   ...  // build sdpOffer
   dum->send(dum->makeInviteSessionFromRefer(msg, ss, sdpOffer);  // send new INVITE
} 

Receiving INVITE with Replaces

When you receive an INVITE request (via the onNewSession callback) you may wish to see if a Replace header is present, in order for this new INVITE session to "take over" an existing session. In order to accomplish this you can use a convience function on the DialogUsageManager called findInviteSession which takes a Replaces header as an argument.

Sample Code:

if(msg->exits(h_Replaces))
{
   pair<InviteSessionHandle, int> presult;
   presult = dum->findInviteSession(msg->header(h_Replaces));
   if(presult != InviteSessionHandle::NotValid())
   {
       ... // Do stuff in app to swap contexts
       Presult.first->end(); // end original session
   }
}