RTSP server find RTP src port in gstreamer

Hi guys,
I’m new in RTSP server Gstreamer, I want find out source port and destination port of RTP packet when a client connect to RTSP server with UDP transport. actually my RTSP server is behind NAT and I want use UPNP to dynamically port forward.
This is my source code

static void on_ssrc_active (GObject * session, GObject * source, GstRTSPMedia * media) { GstStructure *stats;
  GST_INFO ("source %p in session %p is active", source, session);

  g_object_get (source, "stats", &stats, NULL);
  if (stats) {
    gchar *sstr;

    sstr = gst_structure_to_string (stats);
    g_print ("structure: %s\n", sstr);
    g_free (sstr);

    gst_structure_free (stats);
  }
}

static void
on_sender_ssrc_active (GObject * session, GObject * source,
    GstRTSPMedia * media)
{
  GstStructure *stats;

  GST_INFO ("source %p in session %p is active", source, session);

  g_object_get (source, "stats", &stats, NULL);
  if (stats) {
    gchar *sstr;

    sstr = gst_structure_to_string (stats);
    g_print ("Sender stats:\nstructure: %s\n", sstr);
    g_free (sstr);

    gst_structure_free (stats);
  }
}


static void
media_prepared_cb (GstRTSPMedia * media)
{
  guint i, n_streams;

  n_streams = gst_rtsp_media_n_streams (media);

  GST_INFO ("media %p is prepared and has %u streams", media, n_streams);

  for (i = 0; i < n_streams; i++) {
    GstRTSPStream *stream;
    GObject *session;

    stream = gst_rtsp_media_get_stream (media, i);
    if (stream == NULL)
      continue;

    session = gst_rtsp_stream_get_rtpsession (stream);
    GST_INFO ("watching session %p on stream %u", session, i);
    gst_rtsp_session_get_header((GstRTSPSession *)session);

    
  
    g_signal_connect (session, "on-ssrc-active",
        (GCallback) on_ssrc_active, media);
    g_signal_connect (session, "on-sender-ssrc-active",
        (GCallback) on_sender_ssrc_active, media);
  }
}

void static media_configure_handler(GstRTSPMediaFactory *factory, GstRTSPMedia *media,
                                    udp *This) {

g_signal_connect (media, "prepared", (GCallback) media_prepared_cb, factory); }

I tried above code but it didn’t work.
Thanks so much.

No body can help? I need find assigned port in udp rtp for rtsp server
Thanks.