1、前端界面代码

　　前端不是重点，够用就行，下面是前端界面，具体代码可到github下载。

2、服务器端搭建

　　本服务器需要提供两个功能：http服务和websocket服务，由于node的事件驱动机制，可将两种服务搭建在同一个端口下。

　　1、包描述文件：package.json,这里用到了两个依赖项，mime：确定静态文件mime类型，socket.io:搭建websocket服务，然后使用npm install  安装依赖

{
 "name": "chat_room",
 "version": "1.0.0",
 "description": "this is a room where you can chat with your friends",
 "main": "index.js",
 "scripts": {
  "test": "echo \"Error: no test specified\" && exit 1"
 },
 "author": "sfs",
 "license": "ISC",
 "dependencies": {
  "socket.io":"2.0.3",
  "mime":"1.3.6"
 }
}

　　2、http服务器

　　http服务主要是给web浏览器提供静态文件，既浏览器发来一个请求，服务器返回一个响应。

const 
  http=require('http'),
  fs=require('fs'),
  path=require('path'),
  mime=require('mime'),
  chatServer=require('./lib/chat_server');

var cache={};//缓存静态文件内容
//发送错误响应
function send404(response){
  response.writeHead(404,{'Content-Type':'text/plain'});
  response.write('Error 4.4:文件未找到。');
  response.end();
}
//发送文件内容
function sendFile(response,filePath,fileContents){
  response.writeHead(
    200,
    {"content-Type":mime.lookup(path.basename(filePath))}
  );
  response.end(fileContents);
}
//查找文件
function serveStatic(response,cache,absPath){
  if(cache[absPath]){
    sendFile(response,absPath,cache[absPath]);
  }else{
    fs.exists(absPath,function(exists){
      if(exists){
        fs.readFile(absPath,function(err,data){
          if(err){
            send404(response);
          }else{
            cache[absPath]=data;
            sendFile(response,absPath,data);
          }
        });
      }else{
        send404(response);
      }
    });
  }
}
//入口
var server=http.createServer(function(request,response){
  var filePath=false;
  console.log(`new request for ${request.url}`);
  if(request.url==='/'){
    filePath='public/index.html';
  }else{
    filePath='public'+request.url;
  }

  var absPath='./'+filePath;
  serveStatic(response,cache,absPath);
});
server.listen(3000,function(){
  console.log("the server is listening on prot 3000.");
});
chatServer.listen(server); //websocket服务也绑定到该端口上

　　3、socket服务

　　socket.io提供了开箱既用的虚拟通道，所以不需要任务手动转发消息到已连接的的用户，可以使用 socket.broadcast.to(room).emit('message','hello'); room为某个聊天室id

const 
  socketio=require('socket.io');
var io,
  guestNumber=1, //用户编号
  nickNames={},  //socket id对应的nickname
  namesUsed={},  //所有已使用的nickname
  allRooms={},  //聊天室--人数
  currentRoom={}; //sockid--聊天室
module.exports.listen=function(server){
  io=socketio.listen(server);
  io.serveClient('log level',1);
  io.sockets.on('connection',function(socket){
    guestNumber=assignGuestName(socket,guestNumber,nickNames);
    joinRoom(socket,'Lobby');
    handleMessageBroadcasting(socket,nickNames);
    handleNameChangeAttempts(socket,nickNames,namesUsed);
    handleRoomJoining(socket);
    socket.on('rooms',function(){
      socket.emit('rooms',JSON.stringify(allRooms));
    });
    handleClientDisconnection(socket,nickNames,namesUsed);
  });
};
//新socket连入，自动分配一个昵称
function assignGuestName(socket,guesetNumber,nickNames){
  var name='Guest'+guestNumber;
  nickNames[socket.id]=name;
  socket.emit('nameResult',{
    success:true,
    name:name
  });
  namesUsed[name]=1;
  return guestNumber+1;
}
//加入某个聊天室
function joinRoom(socket,room){
  socket.join(room);
  var num=allRooms[room];
  if(num===undefined){
    allRooms[room]=1;
  }else{
    allRooms[room]=num+1;
  }
  currentRoom[socket.id]=room;
  socket.emit('joinResult',{room:room});
  socket.broadcast.to(room).emit('message',{
    text:nickNames[socket.id]+' has join '+room+'.'
  });
  var usersinRoom=io.sockets.adapter.rooms[room];
  if(usersinRoom.length>1){
    var usersInRoomSummary='Users currently in '+room+' : ';
    for(var index in usersinRoom.sockets){
      if(index!=socket.id){
        usersInRoomSummary+=nickNames[index]+',';
      }
    }
    socket.emit('message',{text:usersInRoomSummary}); 
  }
}
//修改昵称
function handleNameChangeAttempts(socket,nickNames,namesUsed){
  socket.on('nameAttempt',function(name){
    if(name.indexOf('Guest')==0){
      socket.emit('nameResult',{
        success:false,
        message:'Names cannot begin with "Guest".'
      });
    }else{
      if(namesUsed[name]==undefined){
        var previousName=nickNames[socket.id];
        delete namesUsed[previousName];
        namesUsed[name]=1;
        nickNames[socket.id]=name;
        socket.emit('nameResult',{
          success:true,
          name:name
        });
        socket.broadcast.to(currentRoom[socket.id]).emit('message',{
          text:previousName+' is now known as '+name+'.'
        });
      }else{
        socket.emit('nameResult',{
          success:false,
          message:'That name is already in use.' 
        });
      }
    }
  });                                    
}
//将某个用户的消息广播到同聊天室下的其他用户
function handleMessageBroadcasting(socket){
  socket.on('message',function(message){
    console.log('message:---'+JSON.stringify(message));
    socket.broadcast.to(message.room).emit('message',{
      text:nickNames[socket.id]+ ': '+message.text
    });
  });
}
//加入/创建某个聊天室
function handleRoomJoining(socket){
  socket.on('join',function(room){
    var temp=currentRoom[socket.id];
    delete currentRoom[socket.id];
    socket.leave(temp);
    var num=--allRooms[temp];
    if(num==0)
      delete allRooms[temp];
    joinRoom(socket,room.newRoom);
  });
}
//socket断线处理
function handleClientDisconnection(socket){
  socket.on('disconnect',function(){
    console.log("xxxx disconnect");
    allRooms[currentRoom[socket.id]]--;
    delete namesUsed[nickNames[socket.id]];
    delete nickNames[socket.id];
    delete currentRoom[socket.id];
  })
}

3、客户端实现socket.io

　　1、chat.js处理发送消息，变更房间，聊天命令。

var Chat=function(socket){
  this.socket=socket;//绑定socket
}
//发送消息
Chat.prototype.sendMessage=function(room,text){
  var message={
    room:room,
    text:text
  };
  this.socket.emit('message',message);
};
//变更房间
Chat.prototype.changeRoom=function(room){
  this.socket.emit('join',{
    newRoom:room
  });
};
//处理聊天命令
Chat.prototype.processCommand=function(command){
  var words=command.split(' ');
  var command=words[0].substring(1,words[0].length).toLowerCase();
  var message=false;
  switch(command){
    case 'join':
      words.shift();
      var room=words.join(' ');
      this.changeRoom(room);
      break;
    case 'nick':
      words.shift();
      var name=words.join(' ');
      this.socket.emit('nameAttempt',name);
      break;
    default:
      message='Unrecognized command.';
      break;
  }
  return message;
};

　　2、chat_ui.js 处理用户输入，根据输入调用chat.js的不同方法发送消息给服务器

function divEscapedContentElement(message){
  return $('<div></div>').text(message);
}
function divSystemContentElement(message){
  return $('<div></div>').html('<i>'+message+'</i>');
}
function processUserInput(chatApp,socket){
  var message=$('#send-message').val();
  var systemMessage;
  if(message.charAt(0)=='/'){
    systemMessage=chatApp.processCommand(message);
    if(systemMessage){
      $('#messages').append(divSystemContentElement(systemMessage));
    }
  }else{
    chatApp.sendMessage($('#room').text(),message);
    $('#messages').append(divSystemContentElement(message));
    $('#messages').scrollTop($('#messages').prop('scrollHeight'));
  }
  $('#send-message').val('');
}

　　3、init.js客户端程序初始化   创建一个websocket连接，绑定事件。

if(window.WebSocket){
  console.log('This browser supports WebSocket');
}else{
  console.log('This browser does not supports WebSocket');
}
var socket=io.connect();
$(document).ready(function(){
  var chatApp=new Chat(socket);
  socket.on('nameResult',function(result){
    var message;
    if(result.success){
      message='You are known as '+result.name+'.';
    }else{
      message=result.message;
    }
    console.log("nameResult:---"+message);
    $('#messages').append(divSystemContentElement(message));
    $('#nickName').text(result.name);
  });
  socket.on('joinResult',function(result){
    console.log('joinResult:---'+result);
    $('#room').text(result.room);
    $('#messages').append(divSystemContentElement('Room changed.'));
  });
  socket.on('message',function(message){
    console.log('message:---'+message);
    var newElement=$('<div></div>').text(message.text);
    $('#messages').append(newElement);
    $('#messages').scrollTop($('#messages').prop('scrollHeight'));
  });
  socket.on('rooms',function(rooms){
    console.log('rooms:---'+rooms);
    rooms=JSON.parse(rooms);
    $('#room-list').empty();
    for(var room in rooms){
      $('#room-list').append(divEscapedContentElement(room+':'+rooms[room]));
    }
    $('#room-list div').click(function(){
      chatApp.processCommand('/join '+$(this).text().split(':')[0]);
      $('#send-message').focus();
    });
  });
  setInterval(function(){
    socket.emit('rooms');
  },1000);
  $('#send-message').focus();
  $('#send-button').click(function(){
    processUserInput(chatApp,socket);
  });
});

完整代码，可到https://github.com/FleyX/ChatRoom 下载。