WebSocket是HTML5開始提供的一種瀏覽器與伺服器間進行全雙工通訊的網路技術。在WebSocket API中，瀏覽器和伺服器只需要要做一個握手(handshaking)的動作，然後，瀏覽器和伺服器之間就形成了一條快速通道。兩者之間就直接可以資料互相傳送。

WebSocket是一個通訊的協議，分為伺服器和客戶端。伺服器放在後臺，保持與客戶端的長連線，完成雙方通訊的任務。客戶端一般都是實現在支援HTML5瀏覽器核心中，通過提供Javascript API使用網頁可以建立websocket連線。

1 為什麼用Nodejs

1. 事件驅動，通過閉包很容易實現客戶端的生命活期。
2. 不用擔心多執行緒，鎖，平行計算的問題
3. V8引擎速度非常快
4. 對於遊戲來說，寫一遍遊戲邏輯程式碼，前端後端通用。

當然Nodejs也有一些缺點：

1. nodejs更新很快，可能會出現版本聯相容
2. nodejs還不算成熟，還沒有大製作。
3. nodejs不像其他的伺服器，對於不同的連線，不支援程序和執行緒操作。

2 WebSocket-Node

伺服器端配置：

localhost:king-node TaoBangren$ npm install websocket

> [email protected]1.0.22 install /Users/TaoBangren/[email protected]/king-node/node_modules/websocket
> (node
 
-gyp rebuild 2> builderror.log) || (exit 0)

  CXX(target) Release/obj.target/bufferutil/src/bufferutil.o
  SOLINK_MODULE(target) Release/bufferutil.node
  CXX(target) Release/obj.target/validation/src/validation.o
  SOLINK_MODULE(target) Release/validation.node
king-node@0.0.0 /Users/TaoBangren/[email protected]
 
/king-node
└── [email protected]1.0.22  extraneous

增加app.js：

~ vi app.js

// http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
"use strict";

// Optional. You will see this name in eg. 'ps' or 'top' command
process.title = 'node-chat';

// Port where we'll run the websocket server
var webSocketsServerPort = 3001;

// websocket and http servers
var webSocketServer = require('websocket').server;
var http = require('http');

/**
 * Global variables
 */
// latest 100 messages
var history = [ ];
// list of currently connected clients (users)
var clients = [ ];

/**
 * Helper function for escaping input strings
 */
functionhtmlEntities(str){
    return String(str).replace(/&/g, '&').replace(/>/g, '>').replace(/"/g, '"');
}

// Array with some colors
var colors = [ 'red', 'green', 'blue', 'magenta', 'purple', 'plum', 'orange' ];
// ... in random order
colors.sort(function(a,b){ return Math.random() > 0.5; } );

/**
 * HTTP server
 */
var server = http.createServer(function(request, response){
    // Not important for us. We're writing WebSocket server, not HTTP server
});
server.listen(webSocketsServerPort, function(){
    console.log((new Date()) + " Server is listening on port " + webSocketsServerPort);
});

/**
 * WebSocket server
 */
var wsServer = new webSocketServer({
    // WebSocket server is tied to a HTTP server. WebSocket request is just
    // an enhanced HTTP request. For more info http://tools.ietf.org/html/rfc6455#page-6
    httpServer: server
});

// This callback function is called every time someone
// tries to connect to the WebSocket server
wsServer.on('request', function(request){
    console.log((new Date()) + ' Connection from origin ' + request.origin + '.');

    // accept connection - you should check 'request.origin' to make sure that
    // client is connecting from your website
    // (http://en.wikipedia.org/wiki/Same_origin_policy)
    var connection = request.accept(null, request.origin); 
    // we need to know client index to remove them on 'close' event
    var index = clients.push(connection) - 1;
    var userName = false;
    var userColor = false;

    console.log((new Date()) + ' Connection accepted.');

    // send back chat history
    if (history.length > 0) {
        connection.sendUTF(JSON.stringify( { type: 'history', data: history} ));
    }

    // user sent some message
    connection.on('message', function(message){
        if (message.type === 'utf8') { // accept only text
            if (userName === false) { // first message sent by user is their name
                // remember user name
                userName = htmlEntities(message.utf8Data);
                // get random color and send it back to the user
                userColor = colors.shift();
                connection.sendUTF(JSON.stringify({ type:'color', data: userColor }));
                console.log((new Date()) + ' User is known as: ' + userName
                            + ' with ' + userColor + ' color.');

            } else { // log and broadcast the message
                console.log((new Date()) + ' Received Message from '
                            + userName + ': ' + message.utf8Data);

                // we want to keep history of all sent messages
                var obj = {
                    time: (new Date()).getTime(),
                    text: htmlEntities(message.utf8Data),
                    author: userName,
                    color: userColor
                };
                history.push(obj);
                history = history.slice(-100);

                // broadcast message to all connected clients
                var json = JSON.stringify({ type:'message', data: obj });
                for (var i=0; i < clients.length; i++) {
                    clients[i].sendUTF(json);
                }
            }
        }
    });

    // user disconnected
    connection.on('close', function(connection){
        if (userName !== false && userColor !== false) {
            console.log((new Date()) + " Peer "
                + connection.remoteAddress + " disconnected.");
            // remove user from the list of connected clients
            clients.splice(index, 1);
            // push back user's color to be reused by another user
            colors.push(userColor);
        }
    });
});

啟動伺服器：

~ D:\workspace\javascript\nodejs-websocket>node app.js
Warning: Native modules not compiled.  XOR performance will be degraded.
Warning: Native modules not compiled.  UTF-8 validation disabled.
Wed Aug 21 2013 15:28:48 GMT+0800 (中國標準時間) Server is listening on port 3001
Wed Aug 21 2013 15:28:53 GMT+0800 (中國標準時間) Connection from origin null.
Wed Aug 21 2013 15:28:53 GMT+0800 (中國標準時間) Connection accepted.
Wed Aug 21 2013 15:28:53 GMT+0800 (中國標準時間) User is known as: Conan with red color.
Wed Aug 21 2013 15:28:53 GMT+0800 (中國標準時間) Peer undefined disconnected.

我們看到XOR 和UTF-8 validation 兩個模組是被禁止的，不過不影響測試。

客戶端，還是使用一樣的。

另外，WebSocket-Node還提供C/S模式的互動，可以不使用瀏覽器：

服務端程式碼：

~ vi app2.js

#!/usr/bin/env node
var WebSocketServer = require('websocket').server;
var http = require('http');

var server = http.createServer(function(request, response){
    console.log((new Date()) + ' Received request for ' + request.url);
    response.writeHead(404);
    response.end();
});
server.listen(3001, function(){
    console.log((new Date()) + ' Server is listening on port 3001');
});

wsServer = new WebSocketServer({
    httpServer: server,
    // You should not use autoAcceptConnections for production
    // applications, as it defeats all standard cross-origin protection
    // facilities built into the protocol and the browser.  You should
    // *always* verify the connection's origin and decide whether or not
    // to accept it.
    autoAcceptConnections: false
});

functionoriginIsAllowed(origin){
  // put logic here to detect whether the specified origin is allowed.
  return true;
}

wsServer.on('request', function(request){
    if (!originIsAllowed(request.origin)) {
      // Make sure we only accept requests from an allowed origin
      request.reject();
      console.log((new Date()) + ' Connection from origin ' + request.origin + ' rejected.');
      return;
    }

    var connection = request.accept('echo-protocol', request.origin);
    console.log((new Date()) + ' Connection accepted.');
    connection.on('message', function(message){
        if (message.type === 'utf8') {
            console.log('Received Message: ' + message.utf8Data);
            connection.sendUTF(message.utf8Data);
        }
        else if (message.type === 'binary') {
            console.log('Received Binary Message of ' + message.binaryData.length + ' bytes');
            connection.sendBytes(message.binaryData);
        }
    });
    connection.on('close', function(reasonCode, description){
        console.log((new Date()) + ' Peer ' + connection.remoteAddress + ' disconnected.');
    });
});

客戶端程式碼：

~ vi client.js

#!/usr/bin/env node
var WebSocketClient = require('websocket').client;

var client = new WebSocketClient();

client.on('connectFailed', function(error){
    console.log('Connect Error: ' + error.toString());
});

client.on('connect', function(connection){
    console.log('WebSocket client connected');
    connection.on('error', function(error){
        console.log("Connection Error: " + error.toString());
    });
    connection.on('close', function(){
        console.log('echo-protocol Connection Closed');
    });
    connection.on('message', function(message){
        if (message.type === 'utf8') {
            console.log("Received: '" + message.utf8Data + "'");
        }
    });

    functionsendNumber(){
        if (connection.connected) {
            var number = Math.round(Math.random() * 0xFFFFFF);
            connection.sendUTF(number.toString());
            setTimeout(sendNumber, 1000);
        }
    }
    sendNumber();
});

client.connect('ws://localhost:3001/', 'echo-protocol');

程式啟動：

~ D:\workspace\javascript\nodejs-websocket>node app2.js
~ D:\workspace\javascript\nodejs-websocket>node client.js

測試成功！！

3 faye-websocket-node

伺服器端配置：

~ D:\workspace\javascript>mkdir nodejs-faye-websocket
~ D:\workspace\javascript>cd nodejs-faye-websocket
~ D:\workspace\javascript\nodejs-faye-websocket>npm install faye-websocket
npm http GET https://registry.npmjs.org/faye-websocket
npm http 304 https://registry.npmjs.org/faye-websocket
npm http GET https://registry.npmjs.org/faye-websocket/-/faye-websocket-0.6.1.tgz
npm http 200 https://registry.npmjs.org/faye-websocket/-/faye-websocket-0.6.1.tgz
npm http GET https://registry.npmjs.org/websocket-driver
npm http 200 https://registry.npmjs.org/websocket-driver
npm http GET https://registry.npmjs.org/websocket-driver/-/websocket-driver-0.2.2.tgz
npm http 200 https://registry.npmjs.org/websocket-driver/-/websocket-driver-0.2.2.tgz
[email protected]0.6.1 node_modules\faye-websocket
└── [email protected]0.2.2

~ vi app.js
var WebSocket = require('faye-websocket'),
    http      = require('http');

var server = http.createServer();

server.on('upgrade', function(request, socket, body) {
  if (WebSocket.isWebSocket(request)) {
    var ws = new WebSocket(request, socket, body);

    ws.on('message', function(event) {
      ws.send(event.data);
    });

    ws.on('close', function(event) {
      console.log('close', event.code, event.reason);
      ws = null;
    });
  }
});

server.listen(3001);

~ D:\workspace\javascript\nodejs-faye-websocket>node app.js

用網頁客戶端訪問：

測試成功，非常簡單！！而且，沒有依賴其他的庫！！

4 socket.io

環境配置：

~ D:\workspace\javascript>express -e nodejs-socketio
~ D:\workspace\javascript>cd nodejs-socketio && npm install
~ D:\workspace\javascript\nodejs-socketio>npm install socket.io

修改app.js配置檔案

~ vi app.js

var app = require('express')();
var server = require('http').createServer(app);
var io = require('socket.io').listen(server);

server.listen(80);

app.get('/', function(req, res){
    res.sendfile(__dirname + '/client/index.html');
});

io.sockets.on('connection', function(socket){
    socket.emit('news', { hello: 'world' });
    socket.on('my other event', function(data){
        console.log(data);
    });
});

增加客戶端檔案，注意這個的index.html要根據app.js指定的位置”res.sendfile(__dirname + ‘/client/index.html’);”

~ mkdir client
~ vi /client/index.html

<!DOCTYPE html>
<html>
<head>
<title>socket.io</title>
<linkrel='stylesheet'href='/stylesheets/style.css' />
</head>
<body>
<h1>socket.io</h1>
<p>Welcome to socket.io</p>

<scriptsrc="/socket.io/socket.io.js"></script>
<script>
var socket = io.connect('http://localhost');
socket.on('news', function (data) {
    console.log(data);
    socket.emit('my other event', { my: 'data' });
});
</script>
</body>
</html>

啟動伺服器：

~ D:\workspace\javascript\nodejs-socketio>node app.js
   info  - socket.io started

檢視伺服器日誌：

debug - served static content /socket.io.js
   debug - client authorized
   info  - handshake authorized ZR-xQhsKCCqM03TRHW4b
   debug - setting request GET /socket.io/1/websocket/ZR-xQhsKCCqM03TRHW4b
   debug - set heartbeat interval for client ZR-xQhsKCCqM03TRHW4b
   debug - client authorized for
   debug - websocket writing 1::
   debug - websocket writing 5:::{"name":"news","args":[{"hello":"world"}]}
{ my: 'data' }
   debug - emitting heartbeat for client ZR-xQhsKCCqM03TRHW4b
   debug - websocket writing 2::
   debug - set heartbeat timeout for client ZR-xQhsKCCqM03TRHW4b
   debug - got heartbeat packet
   deb