一. 背景
最近的一個專案：需要使用 Android App 作為 Socket 的服務端，並且一個埠能夠同時監聽 TCP/Web Socket 協議。
自然而然，專案決定採用 Netty 框架。Netty 服務端在收到客戶端發來的訊息後，能夠做出相應的業務處理。在某些場景下，服務端也需要給客戶端 App/網頁傳送訊息。
二. Netty 的使用
2.1 Netty 服務端
首先，定義好 NettyServer，它使用object宣告表示是一個單例。用於 Netty 服務端的啟動、關閉以及傳送訊息。
object NettyServer {
private val TAG = "NettyServer"
private var channel: Channel?=null
private lateinit var listener: NettyServerListener<String>
private lateinit var bossGroup: EventLoopGroup
private lateinit var workerGroup: EventLoopGroup
var port = 8888
set(value) {
field = value
}
var webSocketPath = "/ws"
set(value) {
field = value
}
var isServerStart: Boolean = false
private set
fun start() {
object : Thread() {
override fun run() {
super.run()
bossGroup = NioEventLoopGroup(1)
workerGroup = NioEventLoopGroup()
try {
val b = ServerBootstrap()
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel::class.java)
.localAddress(InetSocketAddress(port))
.childOption(ChannelOption.SO_KEEPALIVE, true)
.childOption(ChannelOption.SO_REUSEADDR, true)
.childOption(ChannelOption.TCP_NODELAY, true)
.childHandler(NettyServerInitializer(listener,webSocketPath))
// Bind and start to accept incoming connections.
val f = b.bind().sync()
Log.i(TAG, NettyServer::class.java.name + " started and listen on " + f.channel().localAddress())
isServerStart = true
listener.onStartServer()
f.channel().closeFuture().sync()
} catch (e: Exception) {
Log.e(TAG, e.localizedMessage)
e.printStackTrace()
} finally {
isServerStart = false
listener.onStopServer()
disconnect()
}
}
}.start()
}
fun disconnect() {
workerGroup.shutdownGracefully()
bossGroup.shutdownGracefully()
}
fun setListener(listener: NettyServerListener<String>) {
this.listener = listener
}
// 非同步傳送TCP訊息
fun sendMsgToClient(data: String, listener: ChannelFutureListener) = channel?.run {
val flag = this.isActive
if (flag) {
this.writeAndFlush(data + System.getProperty("line.separator")).addListener(listener)
}
flag
} ?: false
// 同步傳送TCP訊息
fun sendMsgToClient(data: String) = channel?.run {
if (this.isActive) {
return this.writeAndFlush(data + System.getProperty("line.separator")).awaitUninterruptibly().isSuccess
}
false
} ?: false
// 非同步傳送WebSocket訊息
fun sendMsgToWS(data: String,listener: ChannelFutureListener) = channel?.run {
val flag = this.isActive
if (flag) {
this.writeAndFlush(TextWebSocketFrame(data)).addListener(listener)
}
flag
} ?: false
// 同步傳送TCP訊息
fun sendMsgToWS(data: String) = channel?.run {
if (this.isActive) {
return this.writeAndFlush(TextWebSocketFrame(data)).awaitUninterruptibly().isSuccess
}
false
} ?: false
/**
* 切換通道
* 設定服務端，與哪個客戶端通訊
* @param channel
*/
fun selectorChannel(channel: Channel?) {
this.channel = channel
}
}
複製程式碼NettyServerInitializer 是服務端跟客戶端連線之後使用的 childHandler：
class NettyServerInitializer(private val mListener: NettyServerListener<String>,private val webSocketPath:String) : ChannelInitializer<SocketChannel>() {
@Throws(Exception::class)
public override fun initChannel(ch: SocketChannel) {
val pipeline = ch.pipeline()
pipeline.addLast("active",ChannelActiveHandler(mListener))
pipeline.addLast("socketChoose", SocketChooseHandler(webSocketPath))
pipeline.addLast("string_encoder",StringEncoder(CharsetUtil.UTF_8))
pipeline.addLast("linebased",LineBasedFrameDecoder(1024))
pipeline.addLast("string_decoder",StringDecoder(CharsetUtil.UTF_8))
pipeline.addLast("commonhandler", CustomerServerHandler(mListener))
}
}
複製程式碼NettyServerInitializer 包含了多個 Handler：連線使用的ChannelActiveHandler，協議選擇使用的 SocketChooseHandler，TCP 訊息使用的 StringEncoder、LineBasedFrameDecoder、StringDecoder，以及最終處理訊息的 CustomerServerHandler。
ChannelActiveHandler:
@ChannelHandler.Sharable
class ChannelActiveHandler(var mListener: NettyServerListener<String>) : ChannelInboundHandlerAdapter() {
@Throws(Exception::class)
override fun channelActive(ctx: ChannelHandlerContext) {
val insocket = ctx.channel().remoteAddress() as InetSocketAddress
val clientIP = insocket.address.hostAddress
val clientPort = insocket.port
Log.i("ChannelActiveHandler","新的連線：$clientIP : $clientPort")
mListener.onChannelConnect(ctx.channel())
}
}
複製程式碼SocketChooseHandler 通過讀取訊息來區分是 WebSocket 還是 Socket。如果是 WebSocket 的話，去掉 Socket 使用的相關 Handler。
class SocketChooseHandler(val webSocketPath:String) : ByteToMessageDecoder() {
@Throws(Exception::class)
override fun decode(ctx: ChannelHandlerContext, `in`: ByteBuf, out: List<Any>) {
val protocol = getBufStart(`in`)
if (protocol.startsWith(WEBSOCKET_PREFIX)) {
PipelineAdd.websocketAdd(ctx,webSocketPath)
ctx.pipeline().remove("string_encoder")
ctx.pipeline().remove("linebased")
ctx.pipeline().remove("string_decoder")
}
`in`.resetReaderIndex()
ctx.pipeline().remove(this.javaClass)
}
private fun getBufStart(`in`: ByteBuf): String {
var length = `in`.readableBytes()
if (length > MAX_LENGTH) {
length = MAX_LENGTH
}
// 標記讀位置
`in`.markReaderIndex()
val content = ByteArray(length)
`in`.readBytes(content)
return String(content)
}
companion object {
/** 預設暗號長度為23 */
private val MAX_LENGTH = 23
/** WebSocket握手的協議字首 */
private val WEBSOCKET_PREFIX = "GET /"
}
}
複製程式碼StringEncoder、LineBasedFrameDecoder、StringDecoder 都是 Netty 內建的編、解碼器。其中，LineBasedFrameDecoder 用於解決 TCP粘包/拆包的問題。
CustomerServerHandler:
@ChannelHandler.Sharable
class CustomerServerHandler(private val mListener: NettyServerListener<String>) : SimpleChannelInboundHandler<Any>() {
@Throws(Exception::class)
override fun channelReadComplete(ctx: ChannelHandlerContext) {
}
override fun exceptionCaught(ctx: ChannelHandlerContext,
cause: Throwable) {
cause.printStackTrace()
ctx.close()
}
@Throws(Exception::class)
override fun channelRead0(ctx: ChannelHandlerContext, msg: Any) {
val buff = msg as ByteBuf
val info = buff.toString(CharsetUtil.UTF_8)
Log.d(TAG,"收到訊息內容：$info")
}
@Throws(Exception::class)
override fun channelRead(ctx: ChannelHandlerContext, msg: Any) {
if (msg is WebSocketFrame) { // 處理 WebSocket 訊息
val webSocketInfo = (msg as TextWebSocketFrame).text().trim { it <= ' ' }
Log.d(TAG, "收到WebSocketSocket訊息：$webSocketInfo")
mListener.onMessageResponseServer(webSocketInfo , ctx.channel().id().asShortText())
} else if (msg is String){ // 處理 Socket 訊息
Log.d(TAG, "收到socket訊息：$msg")
mListener.onMessageResponseServer(msg, ctx.channel().id().asShortText())
}
}
// 斷開連線
@Throws(Exception::class)
override fun channelInactive(ctx: ChannelHandlerContext) {
super.channelInactive(ctx)
Log.d(TAG, "channelInactive")
val reAddr = ctx.channel().remoteAddress() as InetSocketAddress
val clientIP = reAddr.address.hostAddress
val clientPort = reAddr.port
Log.d(TAG,"連線斷開：$clientIP : $clientPort")
mListener.onChannelDisConnect(ctx.channel())
}
companion object {
private val TAG = "CustomerServerHandler"
}
}
複製程式碼2.2 Netty 客戶端
客戶端也需要一個啟動、關閉、傳送訊息的 NettyTcpClient，並且 NettyTcpClient 的建立採用 Builder 模式。
class NettyTcpClient private constructor(val host: String, val tcp_port: Int, val index: Int) {
private lateinit var group: EventLoopGroup
private lateinit var listener: NettyClientListener<String>
private var channel: Channel? = null
/**
* 獲取TCP連線狀態
*
* @return 獲取TCP連線狀態
*/
var connectStatus = false
/**
* 最大重連次數
*/
var maxConnectTimes = Integer.MAX_VALUE
private set
private var reconnectNum = maxConnectTimes
private var isNeedReconnect = true
var isConnecting = false
private set
var reconnectIntervalTime: Long = 5000
private set
/**
* 心跳間隔時間
*/
var heartBeatInterval: Long = 5
private set//單位秒
/**
* 是否傳送心跳
*/
var isSendheartBeat = false
private set
/**
* 心跳資料，可以是String型別，也可以是byte[].
*/
private var heartBeatData: Any? = null
fun connect() {
if (isConnecting) {
return
}
val clientThread = object : Thread("Netty-Client") {
override fun run() {
super.run()
isNeedReconnect = true
reconnectNum = maxConnectTimes
connectServer()
}
}
clientThread.start()
}
private fun connectServer() {
synchronized(this@NettyTcpClient) {
var channelFuture: ChannelFuture?=null
if (!connectStatus) {
isConnecting = true
group = NioEventLoopGroup()
val bootstrap = Bootstrap().group(group)
.option(ChannelOption.TCP_NODELAY, true)//遮蔽Nagle演算法試圖
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000)
.channel(NioSocketChannel::class.java as Class<out Channel>?)
.handler(object : ChannelInitializer<SocketChannel>() {
@Throws(Exception::class)
public override fun initChannel(ch: SocketChannel) {
if (isSendheartBeat) {
ch.pipeline().addLast("ping", IdleStateHandler(0, heartBeatInterval, 0, TimeUnit.SECONDS)) //5s未傳送資料，回撥userEventTriggered
}
ch.pipeline().addLast(StringEncoder(CharsetUtil.UTF_8))
ch.pipeline().addLast(StringDecoder(CharsetUtil.UTF_8))
ch.pipeline().addLast(LineBasedFrameDecoder(1024))//黏包處理,需要客戶端、服務端配合
ch.pipeline().addLast(NettyClientHandler(listener, index, isSendheartBeat, heartBeatData))
}
})
try {
channelFuture = bootstrap.connect(host, tcp_port).addListener {
if (it.isSuccess) {
Log.d(TAG, "連線成功")
reconnectNum = maxConnectTimes
connectStatus = true
channel = channelFuture?.channel()
} else {
Log.d(TAG, "連線失敗")
connectStatus = false
}
isConnecting = false
}.sync()
// Wait until the connection is closed.
channelFuture.channel().closeFuture().sync()
Log.d(TAG, " 斷開連線")
} catch (e: Exception) {
e.printStackTrace()
} finally {
connectStatus = false
listener.onClientStatusConnectChanged(ConnectState.STATUS_CONNECT_CLOSED, index)
if (channelFuture != null) {
if (channelFuture.channel() != null && channelFuture.channel().isOpen) {
channelFuture.channel().close()
}
}
group.shutdownGracefully()
reconnect()
}
}
}
}
fun disconnect() {
Log.d(TAG, "disconnect")
isNeedReconnect = false
group.shutdownGracefully()
}
fun reconnect() {
Log.d(TAG, "reconnect")
if (isNeedReconnect && reconnectNum > 0 && !connectStatus) {
reconnectNum--
SystemClock.sleep(reconnectIntervalTime)
if (isNeedReconnect && reconnectNum > 0 && !connectStatus) {
Log.e(TAG, "重新連線")
connectServer()
}
}
}
/**
* 非同步傳送
*
* @param data 要傳送的資料
* @param listener 傳送結果回撥
* @return 方法執行結果
*/
fun sendMsgToServer(data: String, listener: MessageStateListener) = channel?.run {
val flag = this != null && connectStatus
if (flag) {
this.writeAndFlush(data + System.getProperty("line.separator")).addListener { channelFuture -> listener.isSendSuccss(channelFuture.isSuccess) }
}
flag
} ?: false
/**
* 同步傳送
*
* @param data 要傳送的資料
* @return 方法執行結果
*/
fun sendMsgToServer(data: String) = channel?.run {
val flag = this != null && connectStatus
if (flag) {
val channelFuture = this.writeAndFlush(data + System.getProperty("line.separator")).awaitUninterruptibly()
return channelFuture.isSuccess
}
false
}?:false
fun setListener(listener: NettyClientListener<String>) {
this.listener = listener
}
/**
* Builder 模式建立NettyTcpClient
*/
class Builder {
/**
* 最大重連次數
*/
private var MAX_CONNECT_TIMES = Integer.MAX_VALUE
/**
* 重連間隔
*/
private var reconnectIntervalTime: Long = 5000
/**
* 伺服器地址
*/
private var host: String? = null
/**
* 伺服器埠
*/
private var tcp_port: Int = 0
/**
* 客戶端標識，(因為可能存在多個連線)
*/
private var mIndex: Int = 0
/**
* 是否傳送心跳
*/
private var isSendheartBeat: Boolean = false
/**
* 心跳時間間隔
*/
private var heartBeatInterval: Long = 5
/**
* 心跳資料，可以是String型別，也可以是byte[].
*/
private var heartBeatData: Any? = null
fun setMaxReconnectTimes(reConnectTimes: Int): Builder {
this.MAX_CONNECT_TIMES = reConnectTimes
return this
}
fun setReconnectIntervalTime(reconnectIntervalTime: Long): Builder {
this.reconnectIntervalTime = reconnectIntervalTime
return this
}
fun setHost(host: String): Builder {
this.host = host
return this
}
fun setTcpPort(tcp_port: Int): Builder {
this.tcp_port = tcp_port
return this
}
fun setIndex(mIndex: Int): Builder {
this.mIndex = mIndex
return this
}
fun setHeartBeatInterval(intervalTime: Long): Builder {
this.heartBeatInterval = intervalTime
return this
}
fun setSendheartBeat(isSendheartBeat: Boolean): Builder {
this.isSendheartBeat = isSendheartBeat
return this
}
fun setHeartBeatData(heartBeatData: Any): Builder {
this.heartBeatData = heartBeatData
return this
}
fun build(): NettyTcpClient {
val nettyTcpClient = NettyTcpClient(host!!, tcp_port, mIndex)
nettyTcpClient.maxConnectTimes = this.MAX_CONNECT_TIMES
nettyTcpClient.reconnectIntervalTime = this.reconnectIntervalTime
nettyTcpClient.heartBeatInterval = this.heartBeatInterval
nettyTcpClient.isSendheartBeat = this.isSendheartBeat
nettyTcpClient.heartBeatData = this.heartBeatData
return nettyTcpClient
}
}
companion object {
private val TAG = "NettyTcpClient"
private val CONNECT_TIMEOUT_MILLIS = 5000
}
}
複製程式碼Android 的客戶端相對而言比較簡單，需要的 Handler 包括：支援心跳的 IdleStateHandler， TCP 訊息需要使用的 Handler (跟服務端一樣分別是StringEncoder、StringDecoder、LineBasedFrameDecoder)，以及對收到 TCP 訊息進行處理的 NettyClientHandler。
NettyClientHandler：
class NettyClientHandler(private val listener: NettyClientListener<String>, private val index: Int, private val isSendheartBeat: Boolean, private val heartBeatData: Any?) : SimpleChannelInboundHandler<String>() {
/**
*
* 設定IdleStateHandler心跳檢測每x秒進行一次讀檢測，
* 如果x秒內ChannelRead()方法未被呼叫則觸發一次userEventTrigger()方法
*
* @param ctx ChannelHandlerContext
* @param evt IdleStateEvent
*/
override fun userEventTriggered(ctx: ChannelHandlerContext, evt: Any) {
if (evt is IdleStateEvent) {
if (evt.state() == IdleState.WRITER_IDLE) { //傳送心跳
if (isSendheartBeat) {
if (heartBeatData == null) {
ctx.channel().writeAndFlush("Heartbeat" + System.getProperty("line.separator")!!)
} else {
if (heartBeatData is String) {
Log.d(TAG, "userEventTriggered: String")
ctx.channel().writeAndFlush(heartBeatData + System.getProperty("line.separator")!!)
} else if (heartBeatData is ByteArray) {
Log.d(TAG, "userEventTriggered: byte")
val buf = Unpooled.copiedBuffer((heartBeatData as ByteArray?)!!)
ctx.channel().writeAndFlush(buf)
} else {
Log.d(TAG, "userEventTriggered: heartBeatData type error")
}
}
} else {
Log.d(TAG, "不傳送心跳")
}
}
}
}
/**
*
* 客戶端上線
*
* @param ctx ChannelHandlerContext
*/
override fun channelActive(ctx: ChannelHandlerContext) {
Log.d(TAG, "channelActive")
listener.onClientStatusConnectChanged(ConnectState.STATUS_CONNECT_SUCCESS, index)
}
/**
*
* 客戶端下線
*
* @param ctx ChannelHandlerContext
*/
override fun channelInactive(ctx: ChannelHandlerContext) {
Log.d(TAG, "channelInactive")
}
/**
* 客戶端收到訊息
*
* @param channelHandlerContext ChannelHandlerContext
* @param msg 訊息
*/
override fun channelRead0(channelHandlerContext: ChannelHandlerContext, msg: String) {
Log.d(TAG, "channelRead0:")
listener.onMessageResponseClient(msg, index)
}
/**
* @param ctx ChannelHandlerContext
* @param cause 異常
*/
override fun exceptionCaught(ctx: ChannelHandlerContext, cause: Throwable) {
Log.e(TAG, "exceptionCaught")
listener.onClientStatusConnectChanged(ConnectState.STATUS_CONNECT_ERROR, index)
cause.printStackTrace()
ctx.close()
}
companion object {
private val TAG = "NettyClientHandler"
}
}
複製程式碼三. Demo 的實現
3.1 Socket 服務端
啟動 NettyServer：
private fun startServer() {
if (!NettyServer.isServerStart) {
NettyServer.setListener(this@MainActivity)
NettyServer.port = port
NettyServer.webSocketPath = webSocketPath
NettyServer.start()
} else {
NettyServer.disconnect()
}
}
複製程式碼NettyServer 非同步傳送 TCP 訊息：
NettyServer.sendMsgToClient(msg, ChannelFutureListener { channelFuture ->
if (channelFuture.isSuccess) {
msgSend(msg)
}
})
複製程式碼NettyServer 非同步傳送 WebSocket 訊息：
NettyServer.sendMsgToWS(msg, ChannelFutureListener { channelFuture ->
if (channelFuture.isSuccess) {
msgSend(msg)
}
})
複製程式碼Demo 可以通過 startServer 來啟動 Socket 服務端，也可以在啟動之前點選 configServer 來修改服務端的埠以及 WebSocket 的 Endpoint。
3.2 Socket 客戶端
NettyTcpClient 通過 Builder 模式建立：
mNettyTcpClient = NettyTcpClient.Builder()
.setHost(ip) //設定服務端地址
.setTcpPort(port) //設定服務端埠號
.setMaxReconnectTimes(5) //設定最大重連次數
.setReconnectIntervalTime(5) //設定重連間隔時間。單位：秒
.setSendheartBeat(false) //設定傳送心跳
.setHeartBeatInterval(5) //設定心跳間隔時間。單位：秒
.setHeartBeatData("I'm is HeartBeatData") //設定心跳資料，可以是String型別，也可以是byte[]，以後設定的為準
.setIndex(0) //設定客戶端標識.(因為可能存在多個tcp連線)
.build()
mNettyTcpClient.setListener(this@MainActivity) //設定TCP監聽
複製程式碼啟動、關閉客戶端連線：
private fun connect() {
Log.d(TAG, "connect")
if (!mNettyTcpClient.connectStatus) {
mNettyTcpClient.connect()//連線伺服器
} else {
mNettyTcpClient.disconnect()
}
}
複製程式碼NettyTcpClient 非同步傳送 TCP 訊息到服務端：
mNettyTcpClient.sendMsgToServer(msg, object : MessageStateListener {
override fun isSendSuccss(isSuccess: Boolean) {
if (isSuccess) {
msgSend(msg)
}
}
})
複製程式碼Demo 的客戶端 App 也可以在啟動之前點選 configClient 來修改要連線的服務端 IP 、埠。
WebSocket 的測試可以通過：www.websocket-test.com/
Netty Server 端跟網頁通訊：
WebSocket線上測試：
四. 總結
藉助 Kotlin 的特性以及 Netty 框架，我們在 Android 上也實現了一個 Socket 服務端。
本文 demo github 地址：github.com/fengzhizi71…
本文的例子很簡單，只是傳送簡單的訊息。在實際生產環境中，我們採用的訊息格式可能是 json ，因為 json 更加靈活，通過解析 json 獲取訊息的內容。
參考資料：
Java與Android技術棧：每週更新推送原創技術文章，歡迎掃描下方的公眾號二維碼並關注，期待與您的共同成長和進步。
