WebRTC：搭建Socket.Io信令服务器（实现简单的聊天室）

效果展示

实现步骤

1.搭建服务端

这里我们用的是nodejs搭建的，由于我们用的不是最新标准的socket.io因此我们需要下载指定版本的socket.io

npm install socket.io@2.0.4

代码如下：

'use strict'
var http = require('http');
var socketio = require('socket.io');
var server = http.createServer(function(req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
});
server.listen(3000, '0.0.0.0');
var io = socketio.listen(server);
io.on('connection', (sokcetClient) => {
    console.log(sokcetClient.id);
    sokcetClient.on('join', (roomId) => {
        //加入房间
        sokcetClient.join(roomId);
        //通知某设备加入房间
        sokcetClient.in(roomId).emit('joined', roomId, sokcetClient.id);
    });
    sokcetClient.on('leave', (roomId) => {
        //离开房间
        sokcetClient.leave(roomId);
        //通知某设备离开房间
        sokcetClient.in(roomId).emit('leaved', roomId, sokcetClient.id);
    });
    sokcetClient.on('sendRoomMsg',(roomId,msg)=>{
        //向房间内推送消息
        sokcetClient.in(roomId).emit('receiveRoomMsg', msg);
    })
});

其中socket.io中部分常用的函数及左右如下：
on：用于监听对应的事件，接收的参数取决于emit发送的数据
emit：用于发送相应的事件
in(roomId).emit：用于在相应的房间内发送事件
join(roomId)：加入相应的房间
leave(roomId)：离开相应的房间

2.客户端实现

1.引入依赖

https://socketio.github.io/socket.io-client-java/installation.html

这里由于服务器不是使用的最新的socketio，因此我们客户端也引入1.0.0版本的库

implementation ('io.socket:socket.io-client:1.0.0') {
        // excluding org.json which is provided by Android
        exclude group: 'org.json', module: 'json'
    }

2.代码实现

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

    </data>

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/white"
        android:padding="10dp"
        tools:context=".MainActivity">
        <Button
            android:id="@+id/bt_connect"
            android:text="连接"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/bt_joinroom"
            android:text="加入房间"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/bt_disConnect"
            android:text="断开连接"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
        <EditText
            android:id="@+id/et_sendmsg"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/bt_sendmsg"
            android:text="发送消息"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
        <TextView
            android:id="@+id/tv_chat"
            android:layout_marginTop="10dp"
            android:padding="10dp"
            android:background="@drawable/shape_chat"
            android:textColor="@color/black"
            android:textSize="15sp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>
</layout>

class MainActivity : AppCompatActivity() {
    private lateinit var mainBinding: ActivityMainBinding
    private var socket: Socket? = null
    private var roomId = "111" //房间号
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mainBinding = DataBindingUtil.setContentView<ActivityMainBinding>(this,R.layout.activity_main)
        mainBinding.lifecycleOwner = this
        initListener()
    }

    private fun initListener() {
        mainBinding.btConnect.setOnClickListener {
            connectSocketIo()
        }
        mainBinding.btDisConnect.setOnClickListener {
            socket?.let {
                //发送离开事件
                it.emit("leave",roomId)
                it.disconnect()
                it.close()
            }
        }
        mainBinding.btJoinroom.setOnClickListener {
            socket?.let {
                //发送加入事件
                it.emit("join",roomId)
            }
        }
        mainBinding.btSendmsg.setOnClickListener {
            var msg = mainBinding.etSendmsg.text.toString()
            //发送消息就是发送sendRoomMsg事件，然后服务器会进行转发
            socket?.let {
                it.emit("sendRoomMsg",roomId,msg)
                addMsg2View(msg)
            }
        }
    }

    private fun connectSocketIo(){
        socket = IO.socket("http://192.168.16.52:3000/").apply {
            connect()
            //接收joined事件，用于提醒有人加入房间了
            on("joined") {
                var roomId = it[0]
                var clientId = it[1]
                Log.e("加入","房间id：$roomId 客户端id：$clientId")
                runOnUiThread {
                    Toast.makeText(this@MainActivity,"客户端：$clientId 加入房间",Toast.LENGTH_SHORT).show()
                }
            }
            //接收receiveRoomMsg事件用于对房间消息的显示
            on("receiveRoomMsg") {
                var roomMsg = it[0]
                runOnUiThread {
                    addMsg2View(roomMsg as String)
                }
            }
        }

    }

    /**
     * 添加消息到控件
     */
    private fun addMsg2View(roomMsg: String) {
        var currentMsg = mainBinding.tvChat.text.toString()
        if(TextUtils.isEmpty(currentMsg)){
            mainBinding.tvChat.text = "$roomMsg"
        }else{
            mainBinding.tvChat.text = "$currentMsg \n $roomMsg"
        }
    }
}