add comments for bug #39

@@ -231,6 +231,8 @@ int SrsRtmpConn::service_cycle()
         // for "some" system control error, 
         // logical accept and retry stream service.
         if (ret == ERROR_CONTROL_RTMP_CLOSE) {
+            // TODO: FIXME: use ping message to anti-death of socket.
+            // @see: https://github.com/winlinvip/simple-rtmp-server/issues/39
             // set timeout to a larger value, for user paused.
             rtmp->set_recv_timeout(SRS_PAUSED_RECV_TIMEOUT_US);
             rtmp->set_send_timeout(SRS_PAUSED_SEND_TIMEOUT_US);