使用go，基于martini，和websocket开发简易聊天室

一、首先，需要了解一下websocket基本原理：here

二、go语言的websocket实现：

基于go语言的websocket也有不少，比如github.com/gorilla/websocket。这里选用的应该算是官方的实现code.google.com/p/go.net/websocket

使用go get安装下载即可。（不过，由于周知的原因:(，我是通过golangtc.com的第三方包下载功能才下载来的）

三、server端

第一个遇到的问题，websocket如何和martini集成？

安装websocket的文档，和http服务集成，应该使用如下方式

func ChatService (ws *websocket.Conn) { for{
　　　　io.Copy(ws,ws);       
    }   
}
http.Handle("/echo", websocket.Handler(EchoServer))

但是，如果注册到martini的route，运行时会报错

m.Any("/chat", websocket.Handler(ChatService))

经阅读Server.go代码，发现，需要使用websocket.Handler的方法ServeHTTP来注册（ps：因为websoket.Handler是个函数签名的自定义类型，所以，我们把ChatService转为websocket.Handler之后，就拥有了它的方法）

m.Any("/chat", websocket.Handler(ChatService).ServeHTTP)

服务端代码，基于某些原因，这里贴上部分代码，其余请大家根据框架自己很容易实现：

type chatMsg struct {

    From      string `json:"from"` 
    To        string `json:"to"`   
    At        string `json:"at"`   
    Type      string `json:"type"` 
    Success   bool        `json:"success"` 
    Msg       string      `json:"msg"`     
    Data      interface{} `json:"data"`    
}
var connections map[*websocket.Conn]*chatClient
var msgQueue *list.List
var locker, lockQueue *sync.RWMutex
var activeClient int64 = 0
var chanNewClient chan *websocket.Conn

func init() {
    connections = make(map[*websocket.Conn]*chatClient)
    msgQueue = list.New()
    locker = &sync.RWMutex{}
    lockQueue = &sync.RWMutex{}
    chanNewClient = make(chan *websocket.Conn, 10)
    go msgMonitor()
}
func ChatService(ws *websocket.Conn) {
    var err error
    var user string
    var hasUser bool
    var session *sessions.Session
    var srvMsg *chatMsg
    defer func() {
        if ex := recover(); ex != nil {
            glog.Errorf("[ChatService]get session panic: %v ,
stack trace:%v", err, debug.Stack())
        }
    }()
    defer deleteClient(ws)
    for {
        if session, err = session_store.Get(ws.Request(), SESSION_NAME); err != nil {
            glog.Errorf("[ChatService]get session error: %v", err)
            return
        }
        hasUser = false
        if iuser, has := session.Values["user"]; has {
            user = iuser.(string)
            hasUser = true
        }

        if hasUser {
            registerClient(ws, user)
        }
        if ptMsg, good, err := readClient(ws); err != nil {
            return
        } else if good {
            if !hasUser && ptMsg.Type != "signin" {
                srvMsg = &chatMsg{From: "server", Success: false, Msg: "signin first please!", Type: "needsignin"}
                if err := sendClient(ws, srvMsg); err != nil {
                    return
                }
            }
            switch ptMsg.Type {
            case "":
                fallthrough
            case "msg":
                if ptMsg.Msg != "" {
                    if err := relayMsg(ws, ptMsg); err != nil {
                        return
                    }
                }
            case "listuser":
                users := getUsersList()
                if jsdata, err := json.Marshal(users); err != nil {
                    srvMsg := &chatMsg{From: "server", Type: "listuser", Success: false, Msg: "get users error:" + err.Error()}
                    if err := sendClient(ws, srvMsg); err != nil {
                        return
                    }
                } else {
                    srvMsg := &chatMsg{From: "server", Type: "listuser", Success: true, Data: string(jsdata)}
                    if err := sendClient(ws, srvMsg); err != nil {
                        return
                    }
                }
            }
        }

    } //end for
}

几点说明：

1如果读写数据遇到错误，甭犹豫，关掉连接；
2活动连接自己记录；
3实现多些的功能，必要定个通讯协议；
4websocket的错误只有一个类型，但是我发现有一个错误内容是”not implemented“的错误（好像来自firefox），可以安全的忽略;

上面第四点，应该是websocket服务缺少什么协议的实现，但是我没看出来，下面是调试信息，有知者望不吝赐教：

2015/01/14 13:43:46 glog.go:169 [[info] [[ChatService] *websocket.ProtocolError when read socket. Request:
Head: [map[Sec-Websocket-Key:[GH09xUWLdTOVB0u3RJdOgA==] User-Agent:[Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)] Cache-Control:[no-cache] Cookie:[my_session=MTQyMTIxNDE2MXxRdXBlSjlVeTR4SG9TVTFSYUJkN1FyMW1GU0c2U05XdjBEc0F0NXZSQnZSbE1BaVdKem51aE44TktZdWNaaUtfaVZBVmVONE9JY1JUcFU0MVliVkFxR3BnUi1LQ2F0RV82b1FxUE9jMXlIV3NGdlhfbWZiLTBSLTQySHFKNmJlVVZJSWlScmpGZXZLWmZuXzc4aXM5UEZQY2ZlRzF8CISa785vyuDilrrpQTg4IKLyiH-U12yGai4ah-ixbV8=] Origin:[http://192.168.5.92:8088] Connection:[Upgrade] Upgrade:[Websocket] Sec-Websocket-Version:[13] Dnt:[1]] 
Body:&struct { http.eofReaderWithWriteTo; io.Closer }{eofReaderWithWriteTo:http.eofReaderWithWriteTo{}, Closer:ioutil.nopCloser{Reader:io.Reader(nil)}}]]]

四、基于网页的client端实现：（客户端浏览器当然需要支持websocket协议，当前最新的浏览器基本都支持了，IE需要10以上）

<!doctype html>
<html>
    <head>
    <title>websocket</title>
    <style>
        #log{height: 300px;overflow-y: scroll;border: 1px solid #CCC;padding:0;}
        #signinpad{display:none;background-color:#99F}
        .r-msg{color:#111;}
        .s-msg{color:#090;}
        .msg-from{font-family:fangsong;}
        .chat-msg{padding-left:15px;}
    </style>
    <script type="text/javascript" src="/js/easyui-1.4.1/jquery.min.js" ></script>
      <script type="text/javascript">
         var sock = null;
         var wsuri = "ws://192.168.5.92:8088/chat";
         $(document).on("ready",function() {
            console.log("onload");
            jQuery.fn.flash = function( size, duration )
            {
                try{
                var current = this.css( 'border-width' );
                if(current=="")current="0px"
                current = parseInt(current)
                this.animate( { 'borderWidth': 5 }, duration / 2 );
                this.animate( { 'borderWidth': current }, duration / 2 );
                }catch(ex){
                    console.log(ex)
                }
            }
            $("#message").on("keydown",function(evt){if(evt.keyCode==13){send();}})
            try{
           　　conn();
            }catch(ex){
                console.log(ex);
                alert("连接websocket务器报错："+ex);
                $("#btnsend").attr("disabled","disabled");
                $("#message").attr("disabled","disabled");
                $("#btngetusers").attr("disabled","disabled");
            }
        });
           function conn(){
                
                    sock = new WebSocket(wsuri);
                      regevt(); 
            }
            function regevt(){
                sock.onopen = function() {
                   console.log("connected to " + wsuri);
                    loaduser();
                }                
                sock.onerror = function(e) {
                   console.log(" error from connect " + e);
                }    
                sock.onclose = function(e) {
                   console.log("connection closed (" + e.code + ")");
                console.log("reconnecting....");
                    setTimeout(   conn,1000);
                }    
                sock.onmessage = onMsg; 
            }
            function onMsg(e) {
               console.log("message received: " + e.data);        
               var msg = window.JSON.parse(e.data);    
               if (msg.type=="" ||msg.type=="msg"){
                   appendMsg(msg.from,msg.msg);
                }else if (msg.type=="needsignin"){
                    alert("signin first,please!");
                    $("#signinpad").css("display","block");
                    $('#btnsignin').removeAttr("disabled")
                    $('#user').focus();
                    $('#btnsignin').on("click",function(){
                        var user = $('#user').val();
                        var pass = $('#password').val();
                        if( user==""){
                            alert("user name cannot be blank!")
                            $('#user').focus();return
                        }
                        if( pass==""){
                            alert("password cannot be blank!")
                            $('#password').focus();return;
                        }
                        appendMsg("self","signining");
                        $('#btnsignin').attr("disabled","disabled")
　　　　　　　　　　　　　　// 这里的url需要替换为你自己web应用的地址，服务需要返回json
                        $.ajax({url:"/api/usr/signin",method:"post",data:{name:user,password:pass},dataType:"json"
                            ,success:function(data){
                                console.log("receive data's type=",typeof(data)," data:",data);                                            
                                if (data.success)    {
                                    onSok();                                
                                }else{
                                    onSerr(data.msg)
                                }
                            }
                            ,error:function(R,err){
                                onSerr(err)
                            }
                        })
                    });
                }else if(msg.type=="listuser"){
                    if(msg.success){
                        var list = $("#userlist");
                        var ind=0;
                        var ccc = list[0].length-1;
                        while (ind<ccc){
                            $("#userlist").get(0).remove(1);
                            ind++;
                        }                    
                        var users = window.JSON.parse(msg.data)
                        for (ind=0;ind<users.length;ind++){
                            list.append("<option value=""+users[ind]+"">"+users[ind]+"</option>")
                        }
                    }else{
                        appendMsg(msg.from,msg.msg);
                    }
                }else if(msg.type=="signin"){
                    if(msg.success){
                        onSok()
                    }else{
                        onSerr(msg.msg);
                    }
                }
                
            }            
         function onSok(){
            $("#signinpad").css("display","none");
            appendMsg("self","signin ok,ready to send message");
            $("#message").focus();
            document.location.href = document.location.href
            sock.send('{"type":"listuser","msg":""}')
            return;
        }
        function onSerr(err){
            appendMsg("self",err)
                appendMsg("self","signin again,please!")
                $('#btnsignin').removeAttr("disabled")
                $('#user').focus();
                return;
        }
        function loaduser(){
            sock.send('{"type":"listuser","msg":""}')
        }
         function send() {
            var msg = $('#message').val();
            if (msg.length==0){
                $("#error").text("enter somthing first!")
                $("#error").flash(5,1000)
                $('#message').on("keydown",function(){$("#error").text("");$('#message').off("keydown");})
                return;
            }else{
                $("#error").text("")
            }
            $('#message').val('');
            var to = $("#userlist").val();
            appendMsg("myself",msg)            
            msgObj={"msg":msg,"type":"msg","to":to};
            jss=window.JSON.stringify(msgObj);
            sock.send(jss);
            console.log("I sent:",jss)
         }

        var lastMsg=""
        function  appendMsg(from,msg){
            msgPad = $('#log');
            if (msg==lastMsg && from=="myself"){
                p=msgPad.find("p:last-child")
                //alert(p[0].outerHTML);
                p.flash(5,500)
                return;
            }
            lastMsg = msg;
            str="";
            if (from=="myself" || from=="self" || from=="me" ||from=="I"){
                from="self"
                str ='<p class="s-msg"><i class="msg-from"> self ';
            }else{
                str ='<p class="r-msg"><i class="msg-from">'+from+' ';
            }            
            str = str+ '('+new Date().toLocaleString()+') :</i> <br/><span class="chat-msg">'+msg+'</span></p>'
            msgPad.append(str);
            msgPad.get(0).scrollTop = $('#log').get(0).scrollHeight;
        }
        function cls(){
            msgPad = $('#log');
            msgPad.empty();
        }
      </script>
    </head>
    <body>
      <h1> 即时网上聊天WebSocket </h1>
          <div id="log">
          </div>
          <div>
            <table >
                <tr id="signinpad" ><td><label for="user">user:</label></td>
                    <td><input id="user" name="user" type="text""></input></td>
                    <td><label for="password">pass:</label></td>
                    <td><input id="password" name="password" type="password"></input></td>
                    <td><input id="btnsignin" name="btnsignin" type="button" value="登录"></input></td>
                </tr>
            <tr><td><label from="userlist">to who:</label></td>
                <td>
                <select id="userlist" style="length:200px;">
                    <option value="all">所有人</option>
                </select>
                </td>
                <td><button id="btngetusers" onclick="loaduser()">rload users</button>
                <td><button id="btncls" onclick="cls()">clear</button>
            </tr>
            
            </table>
                <p>
                    Message: <input id="message" type="text" value="Hello, world!" ><button id="btnsend" onclick="send();">Send Message</button>
                </p>
                <div id="error" style="color:red;"></div>      
          </div>
</body>
</html>

说明：其中，用户登录需要通过form提交到web后台的登录服务，我试着通过websocket自身服务实现登录，没有搞定保存session，不过如果聊天功能绑定在web网站上的话，应该也不需要单独登录功能。