Fail over subscribe with SipSorcery

Question

How is it possible to create a new subscription using SipSorcery, if your TCP connection died within the expiry timer of your initial subscription? Write now I'm having a expiry timer running, and when it elapse, I'm checking if the connection is established like this:

while (!tcpChannel.IsConnectionEstablished(myRemoteEndpoint))
{
    //... using same from tag, but creating new call id saved as SIPRequest _request...
    System.Threading.Thread.Sleep(1000 * 60);
    tcpChannel.Send(myRemoteEndpoint, Encoding.UTF8.GetBytes(_request.ToString());
}

The idea was to wait 60 seconds, then try to send a new SUBSCRIBE to the server, check if the connection is established, if not run again after 60 senconds, until the connection is established.

But the .IsConnectionEstablished seems a little unreliable to this purpose... Its like the while loop blocking for something. I can see that my SUBSCRIBE request has been sended, but I ain't receiving any response on that request.

Any ideas are appriciated.

Answer 1

You shouldn't need to do the IsConnectionEstablished check. When you call tcpChannel.Send it will take care of establishing a new TCP connection to the required end point if one is not available.

As to why you are not receiving a response to your subsequent SUBSCRIBE requests if you are re-sending the same request repeatedly without updating the required headers such as CSeq, Via branchid, Call-ID & from tag then it's probably getting flagged as a duplicate request.

Also you may want to have a look SIPSorcery.SIP.App.SIPNotifierClient as it is designed to maintain a subscription with a SIP server.