用Go+WebSocket快速实现一个chat服务

// HTML 操作 {js}
if (window["WebSocket"]) {
 conn = new WebSocket("ws://" + document.location.host + "/ws");
 conn.onclose = function (evt) {
  var item = document.createElement("div");
  item.innerHTML = "<b>Connection closed.</b>";
  appendLog(item);
 };
 ...
}

// 路由
engine.AddRoute(rest.Route{
 Method: http.MethodGet,
 Path:  "/ws",
 Handler: func(w http.ResponseWriter, r *http.Request) {
  internal.ServeWs(hub, w, r)
 },
})

// 接入逻辑
func ServeWs(hub *Hub, w http.ResponseWriter, r *http.Request) {
 // 将http请求升级为websocket
 conn, err := upgrader.Upgrade(w, r, nil)
 ...
 // 构建client：hub{engine}, con{websocker conn}, send{channel buff}
 client := &Client{
 hub: hub,
 conn: conn,
 send: make(chan []byte, bufSize),
 }
 client.hub.register <- client
 // 开始客户端双工的通信，接收和写入数据
 go client.writePump()
 go client.readPump()
}

type Hub struct {
 clients map[*Client]bool // 上线clients
 broadcast chan []byte  // 客户端发送的消息 ->广播给其他的客户端
 register chan *Client   // 注册channel，接收注册msg
 unregister chan *Client  // 下线channel
}

func (h *Hub) Run() {
 for {
 select {
  // 注册channel：存放到注册表中，数据流也就在这些client中发生
 case client := <-h.register:
  h.clients[client] = true
  // 下线channel：从注册表里面删除
 case client := <-h.unregister:
  if _, ok := h.clients[client]; ok {
  delete(h.clients, client)
  close(client.send)
  }
  // 广播消息：发送给注册表中的client中，send接收到并显示到client上
 case message := <-h.broadcast:
  for client := range h.clients {
  select {
  case client.send <- message:
  default:
   close(client.send)
   delete(h.clients, client)
  }
  }
 }
 }
}

func (c *Client) readPump() {
 ...
 for {
  // 1
 _, message, err := c.conn.ReadMessage()
 if err != nil {
  if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
  log.Printf("error: %v", err)
  }
  break
 }
 message = bytes.TrimSpace(bytes.Replace(message, newline, space, -1))
  // 2.
 c.hub.broadcast <- message
 }
}

func (c *Client) writePump() {
 // 写超时控制
 ticker := time.NewTicker(pingPeriod)
 ...
 for {
 select {
 case message, ok := <-c.send:
   // 当接收消息写入时，延长写超时时间。
  c.conn.SetWriteDeadline(time.Now().Add(writeWait))
  ...
  w, err := c.conn.NextWriter(websocket.TextMessage)
  ...
  w.Write(message)

  // 依次读取 send 中消息，并write
  n := len(c.send)
  for i := 0; i < n; i++ {
  w.Write(newline)
  w.Write(<-c.send)
  }
   ...
 case <-ticker.C:
  c.conn.SetWriteDeadline(time.Now().Add(writeWait))
  ...
 }
 }
}