title: Fail over subscribe with SipSorcery
body: <p>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:</p>
  
  <pre><code>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());
  }
  </code></pre>
  
  <p>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.</p>
  
  <p>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.</p>
  
  <p>Any ideas are appriciated.</p>