国标GB28181协议客户端EasyGBS国标视频平台级联EasyNVR：EasyNVR到EasyGBS上是如何注册及注销的？

func NewClient(cascade Cascade) *Client {
   client := &Client{
      Stoped:        false,
      Cascade:       cascade,
      AckTimeout:    cascade.AckTimeout,
      LocalHost:     cascade.LocalHost,
      LocalPort:     cascade.LocalPort,
      LocalWanIP:    "",
      LocalSerial:   cascade.LocalSerial,
      handleMap:     make(map[string][]HandleFunc),
      dispatcher:    events.NewDispatcher(),
      KeepAliveQuit: make(chan bool, 0),
      RegisterQuit:  make(chan bool, 0),
      DevCache:      cache.New(time.Duration(cascade.KeepaliveTimeout)*time.Second, 10*time.Second),
   }
   return client
}

func (c *Client) Run() {
   if c.LocalPort == 0 {
      log.Println("没有可用的UDP级联端口")
      return
   }
   lUdpAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", c.LocalPort))
   if err != nil {
      return
   }
   rUdpAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", c.Cascade.Host, c.Cascade.Port))
   if err != nil {
      return
   }
   c.udpConn, err = net.DialUDP("udp", lUdpAddr, rUdpAddr)
   if err != nil {
      log.Printf("uac start error:%v", err)
      return
   }
   if e := c.udpConn.SetReadBuffer(UDP_BUF_SIZE); e != nil {
      log.Printf("sip udp set connection read buffer[%d] error, %v", UDP_BUF_SIZE, e)
   }
   if e := c.udpConn.SetWriteBuffer(UDP_BUF_SIZE); e != nil {
      log.Printf("sip udp set connection write buffer[%d] error, %v", UDP_BUF_SIZE, e)
   }
   defer c.udpConn.Close()
   c.Transport = c.NewUDPTransport(rUdpAddr, c.udpConn)
   go c.Register(false)
   log.Printf("uac start ok:%s", c.udpConn.LocalAddr().String())
   c.Stoped = false
   c.Handle("MESSAGE", HandleMessage)
   c.Handle("INVITE", HandleInvite)
   c.Handle("BYE", HandleBye)
   c.Handle("INFO", HandleInfo)
   for !c.Stoped {
      bufUDP := make([]byte, UDP_BUF_SIZE)
      n, _, err := c.udpConn.ReadFromUDP(bufUDP)
      if err != nil {
         log.Printf("udp read error, %v", err)
         continue
      }
      sipBuf := bufUDP[:n]
      sipRaw := string(sipBuf)
      sipMsg := siprocket.Parse(sipBuf)
      statusCode := string(sipMsg.Req.StatusCode)
      contentLen, _ := strconv.Atoi(string(sipMsg.ContLen.Value))
      header := sipRaw[:len(sipRaw)-contentLen]
      body := sipRaw[len(sipRaw)-contentLen:]
      Logf("级联消息：[%s]<<<<<<[%s]<<<<<<\r\n%v", c.udpConn.LocalAddr().String(), c.udpConn.RemoteAddr().String(), sipRaw)
      if statusCode == "" { // request
         req, err := UnmarshalRequest(header, body)
         if err != nil {
            log.Printf("unmarshal request failed, %v", err)
            continue
         }
         req.FixVia(c.Transport)
         c.HandleRequest(req, &sipMsg)
      } else { // response
         res, err := UnmarshalResponse(header, body)
         if err != nil {
            log.Printf("unmarshal response failed, %v", err)
            continue
         }
         callid := res.HeaderMap["Call-ID"]
         cseq := res.HeaderMap["CSeq"]
         c.dispatcher.Dispatch(fmt.Sprintf("%s:%s", callid, cseq), res)
      }
   }
}

func Start() {
   cascade := GetGbsConfig()
   if cascade.Enable != 0 {
      client = NewClient(cascade)
      go client.Run()
   }
   return
}
 
func Stop() {
   if client != nil {
      if !client.Stoped {
         client.Stoped = true
         client.RegisterQuit <- true
         client.KeepAliveQuit <- true
      }
      client = nil
      log.Println("级联stop")
   }
}