public RTPServer GetOrAddServer(string videoId)
 {
     if (_rtpServers.ContainsKey(videoId))
     {
         return(_rtpServers[videoId]);
     }
     else
     {
         int       port = PortUtils.GetFreeRTPPort();
         RTPServer rs   = new RTPServer(port, videoId);
         rs.TargetsCleared   += Rs_TargetsCleared;
         _rtpServers[videoId] = rs;
         return(rs);
     }
 }