[Linphone-developers] oRTP question on RTP peer change

[BOITEUX, Frederic]

        Dear oRTP developpers,

I've tried to analyze an error raised by oRTP (version 0.23) with the following 
scenario :

- On the same machine, an outgoing VoIP call is made to one local peer, then 
another [local] one, then a third [local] one
- The RTP session of the outgoing call is bound   successively to the first 
peer's RTP, then the second, then the third, exchanging data a few seconds with 
each ones.
- With the third peer, about one second after the session is updated, I get an 
oRTP error :
Error receiving RTP packet (code: 111)
code 111 meaning "Connection refused" (ECONNREFUSED)

The difference which can matters  between the first and second peers is that 
the first peer  closes its RTP session after our local call has turned to 
second peer, but the second peer closes its RTP session a little before our 
local call is going to the third peer. In this latter case, I receive a RTCP 
BYE from the second peer, and surely I should do something on the local RTP 
session to stop reading RTP packets  it until a new peer is found ?  is it a  
good analyze ? have you any suggestion on how to do it ?



Trying to understand how this works, I'm puzzled with 
rtp_session_set_remote_addr_full() function regarding to peer change :
In its last part, this function test with can_connect(session) if the socket 
can be connected, and if so, set the bit masks RTP_SOCKET_CONNECTED and 
RTCP_SOCKET_CONNECTED, and if it *doesn't*, it checks if these flags are set 
(but how could they be set ?) and reset the socket connection with a connect() 
with AF_UNSPEC family :
if (can_connect(session)){
        if (try_connect(session->rtp.socket,(struct 
sockaddr*)&session->rtp.rem_addr,session->rtp.rem_addrlen, session))
                session->flags|=RTP_SOCKET_CONNECTED;
        if (session->rtcp.socket>=0){
                if (try_connect(session->rtcp.socket,(struct 
sockaddr*)&session->rtcp.rem_addr,session->rtcp.rem_addrlen, session))
                        session->flags|=RTCP_SOCKET_CONNECTED;
        }
}else if (session->flags & RTP_SOCKET_CONNECTED){
        /*must dissolve association done by connect().
        See connect(2) manpage*/
        struct sockaddr sa;
        sa.sa_family=AF_UNSPEC;
        if (connect(session->rtp.socket,&sa,sizeof(sa))<0){
                ortp_sess_error(session, "Cannot dissolve connect() association 
for rtp socket: %s", getSocketError());
        }
        if (connect(session->rtcp.socket,&sa,sizeof(sa))<0){
                ortp_sess_error(session, "Cannot dissolve connect() association 
for rtcp socket: %s", getSocketError());
        }
        session->flags&=~RTP_SOCKET_CONNECTED;
        session->flags&=~RTCP_SOCKET_CONNECTED;
}

I would have do something like :
if (can_connect(session)) {
        if (session->flags & RTP_SOCKET_CONNECTED) {
                // dissolve association...
        }
        // do try_connect() ...
}


        With regards,
                Fred.

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