Support nat traversal

.gitignore

@@ -16,3 +16,4 @@
 
 dist/
 .vscode/
+.devcontainer/

client/client.go

@@ -26,8 +26,30 @@ type ClientEndpoint struct {
 
 func (c *ClientEndpoint) Start(nt *options.NATTraversalOptions) {
 	if nt.NATTraversalMode {
-		conn := nattraversal.DialUDP(&nattraversal.ConnConfig{Nt: *nt})
-		c.new(conn, conn.Conn.RemoteAddr(), conn.Conn.LocalAddr().String())
+		ctx, cancel := context.WithCancel(context.TODO())
+		defer cancel()
+		connCtrl := nattraversal.NewConnCtrl(nt)
+		go nattraversal.DialUDP(ctx, connCtrl)
+		select {
+		case <-connCtrl.ExitChan:
+			log.Warn("first nat traversal failed, the second nat traversal attempt")
+			// Subscribe and wait for messages from the remote peer
+			connCtrl.MqttClient = nattraversal.NewMQTTClient(connCtrl.Nt, connCtrl.SdCh)
+			nattraversal.Subscribe(connCtrl.MqttClient)
+			connCtrl.RemoteSd = <-connCtrl.SdCh
+			go nattraversal.ListenUDP(ctx, connCtrl)
+			select {
+			case <-connCtrl.ConvertExitChan:
+				log.Warn("nat traversal faild!")
+				cancel()
+			case conn := <-connCtrl.ConnChan:
+				log.Info("nat traversal success!")
+				c.new(conn, conn.Conn.RemoteAddr(), conn.Conn.LocalAddr().String())
+			}
+		case conn := <-connCtrl.ConnChan:
+			log.Infof("nat traversal success! Remote address is %s", conn.Conn.RemoteAddr())
+			c.new(conn, conn.Conn.RemoteAddr(), conn.Conn.LocalAddr().String())
+		}
 	} else {
 		raddr, err := net.ResolveUDPAddr("udp", c.ServerEndpointSocket)
 		if err != nil {