WebSocket
WebSocket协议是一种双向通信协议，它建立在TCP之上，同http一样通过TCP来传输数据，但是它和http最大的不同有两点：
- WebSocket是一种双向通信协议，在建立连接后，WebSocket服务器和Browser/UA都能主动的向对方发送或接收数据，就像Socket一样，不同的是WebSocket是一种建立在Web基础上的一种简单模拟Socket的协议；
- WebSocket需要通过握手连接，类似于TCP它也需要客户端和服务器端进行握手连接，连接成功后才能相互通信。
当Web应用程序调用new WebSocket(url)接口时，Browser就开始了与地址为url的WebServer建立握手连接的过程。
客户端向服务器发送请求：
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key:dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat,superchat
Sec-WebSocket-Version: 13
服务器端返回内容:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: xsOSgr30aKL2GNZKNHKmeT1qYjA=
请求中的【Sec-WebSocket-Key】是随机发送的。而服务器返回的【Sec-WebSocket-Accept】是将【Sec-WebSocket-Key】加上一个固定字符串【258EAFA5-E914-47DA-95CA-C5AB0DC85B11】，并使用SHA-1加密后，再进行BASE-64编码生成的。
服务端简单实例
新建一个Web MVC项目：
.net4.5中实现了对websocket的支持，所以直接在一个项目中新建一个一般处理程序 Handler1 ：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.WebSockets;
namespace WebApplicationWebsocketHandler
{
/// <summary>
/// 离线消息
/// </summary>
public class MessageInfo
{
public MessageInfo(DateTime _MsgTime, ArraySegment<byte> _MsgContent)
{
MsgTime = _MsgTime;
MsgContent = _MsgContent;
}
public DateTime MsgTime { get; set; }
public ArraySegment<byte> MsgContent { get; set; }
}
/// <summary>
/// Handler1 的摘要说明
/// </summary>
public class Handler1 : IHttpHandler
{
private static Dictionary<string, WebSocket> CONNECT_POOL = new Dictionary<string, WebSocket>();//用户连接池
private static Dictionary<string, List<MessageInfo>> MESSAGE_POOL = new Dictionary<string, List<MessageInfo>>();//离线消息池
public void ProcessRequest(HttpContext context)
{
//context.Response.ContentType = "text/plain";
//context.Response.Write("Hello World");
if (context.IsWebSocketRequest)
{
context.AcceptWebSocketRequest(ProcessChat);
}
}
private async Task ProcessChat(AspNetWebSocketContext context)
{
WebSocket socket = context.WebSocket;
string user = context.QueryString["user"].ToString();
try
{
#region 用户添加连接池
//第一次open时，添加到连接池中
if (!CONNECT_POOL.ContainsKey(user))
CONNECT_POOL.Add(user, socket);//不存在，添加
else
if (socket != CONNECT_POOL[user])//当前对象不一致，更新
CONNECT_POOL[user] = socket;
#endregion
#region 离线消息处理
if (MESSAGE_POOL.ContainsKey(user))
{
List<MessageInfo> msgs = MESSAGE_POOL[user];
foreach (MessageInfo item in msgs)
{
await socket.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes(item.MsgTime + ":" + item.MsgContent)), WebSocketMessageType.Text, true, CancellationToken.None);
}
MESSAGE_POOL.Remove(user);//移除离线消息
}
#endregion
string descUser = string.Empty;//目的用户
while (true)
{
if (socket.State == WebSocketState.Open)
{
ArraySegment<byte> buffer = new ArraySegment<byte>(new byte[2048]);
WebSocketReceiveResult result = await socket.ReceiveAsync(buffer, CancellationToken.None);
#region 消息处理（字符截取、消息转发）
try
{
#region 关闭Socket处理，删除连接池
if (socket.State != WebSocketState.Open)//连接关闭
{
if (CONNECT_POOL.ContainsKey(user)) CONNECT_POOL.Remove(user);//删除连接池
break;
}
#endregion
string userMsg = Encoding.UTF8.GetString(buffer.Array, 0, result.Count);//发送过来的消息
string[] msgList = userMsg.Split('|');
if (msgList.Length == 2)
{
if (msgList[0].Trim().Length > 0)
descUser = msgList[0].Trim();//记录消息目的用户
buffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(msgList[1]));
if (CONNECT_POOL.ContainsKey(descUser))//判断客户端是否在线
{
WebSocket destSocket = CONNECT_POOL[descUser];//目的客户端
if (destSocket != null && destSocket.State == WebSocketState.Open)
await destSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
else
{
Task.Run(() =>
{
if (!MESSAGE_POOL.ContainsKey(descUser))//将用户添加至离线消息池中
MESSAGE_POOL.Add(descUser, new List<MessageInfo>());
MESSAGE_POOL[descUser].Add(new MessageInfo(DateTime.Now, buffer));//添加离线消息
});
}
}
else
{
buffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(userMsg));
foreach (KeyValuePair<string, WebSocket> item in CONNECT_POOL)
{
await item.Value.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
}
}
catch (Exception exs)
{
//消息转发异常处理，本次消息忽略 继续监听接下来的消息
}
#endregion
}
else
{
break;
}
}//while end
}
catch (Exception ex)
{
//整体异常处理
if (CONNECT_POOL.ContainsKey(user)) CONNECT_POOL.Remove(user);
}
}
public bool IsReusable
{
get
{
return false;
}
}
}
}
客户端测试代码如下：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0"/>
<title></title>
<script src="http://code.jquery.com/jquery-1.4.1.min.js"></script>
<script>
var ws;
$().ready(function () {
$('#conn').click(function () {
//ws = new WebSocket('ws://' + window.location.hostname + ':' + window.location.port + '/Handler1.ashx?user=' + $("#user").val());
ws = new WebSocket('ws://127.0.0.1:80/Handler1.ashx?user=' + $("#user").val());
//var host = 'ws://192.168.85.128:8085/api/WSChat?user='+$("#user").val();
//var host = "ws://192.168.85.128:8085/api/WSChat";
//webSocket = new WebSocket(host);
$('#msg').append('<p>正在连接</p>');
ws.onopen = function () {
$('#msg').append('<p>已经连接</p>');
}
ws.onmessage = function (evt) {
$('#msg').append('<p>' + evt.data + '</p>');
}
ws.onerror = function (evt) {
$('#msg').append('<p>' + JSON.stringify(evt) + '</p>');
}
ws.onclose = function () {
$('#msg').append('<p>已经关闭</p>');
}
});
$('#close').click(function () {
ws.close();
});
$('#send').click(function () {
if (ws.readyState == WebSocket.OPEN) {
ws.send($("#to").val() + "|" + $('#content').val());
}
else {
$('#tips').text('连接已经关闭');
}
});
});
</script>
</head>
<body>
<div>
<input id="user" type="text" />
<input id="conn" type="button" value="连接" />
<input id="close" type="button" value="关闭"/><br />
<span id="tips"></span>
<input id="content" type="text" />
<input id="send" type="button" value="发送"/><br />
<input id="to" type="text" />目的用户
<div id="msg">
</div>
</div>
</body>
</html>测试需要iis配置支持WebSocket协议，win7暂不支持。。。