websocket/examples/chat/conn.go

// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"github.com/gorilla/websocket"
	"log"
	"net/http"
	"time"
)

const (
	// Time allowed to write a message to the peer.
	writeWait = 10 * time.Second

	// Time allowed to read the next pong message from the peer.
	pongWait = 60 * time.Second

	// Send pings to peer with this period. Must be less than pongWait.
	pingPeriod = (pongWait * 9) / 10

	// Maximum message size allowed from peer.
	maxMessageSize = 512
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

// connection is an middleman between the websocket connection and the hub.
type connection struct {
	// The websocket connection.
	ws *websocket.Conn

	// Buffered channel of outbound messages.
	send chan []byte
}

// readPump pumps messages from the websocket connection to the hub.
func (conn *connection) readPump() {
	defer func() {
		mainHub.unregister <- conn
		conn.ws.Close()
	}()
	conn.ws.SetReadLimit(maxMessageSize)
	conn.ws.SetReadDeadline(time.Now().Add(pongWait))
	conn.ws.SetPongHandler(func(string) error { conn.ws.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, message, err := conn.ws.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway) {
				log.Printf("error: %v", err)
			}
			break
		}
		mainHub.broadcast <- message
	}
}

// write writes a message with the given message type and payload.
func (conn *connection) write(mt int, payload []byte) error {
	conn.ws.SetWriteDeadline(time.Now().Add(writeWait))
	return conn.ws.WriteMessage(mt, payload)
}

// writePump pumps messages from the hub to the websocket connection.
func (conn *connection) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		conn.ws.Close()
	}()
	for {
		select {
		case message, ok := <-conn.send:
			if !ok {
				conn.write(websocket.CloseMessage, []byte{})
				return
			}
			if err := conn.write(websocket.TextMessage, message); err != nil {
				return
			}
		case <-ticker.C:
			if err := conn.write(websocket.PingMessage, []byte{}); err != nil {
				return
			}
		}
	}
}

// serveWs handles websocket requests from the peer.
func serveWs(w http.ResponseWriter, r *http.Request) {
	ws, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}
	conn := &connection{send: make(chan []byte, 256), ws: ws}
	mainHub.register <- conn
	go conn.writePump()
	conn.readPump()
}