java netty 实现 websocket 服务端和客户端双向通信 实现心跳和断线重连 完整示例
maven依赖
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.97.Final</version>
</dependency>服务端
服务端心跳事件处理 ServerHeartbeatHandler
package com.sux.demo.websocket2;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
public class ServerHeartbeatHandler extends ChannelInboundHandlerAdapter {
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
if (evt instanceof IdleStateEvent) {
IdleStateEvent event = (IdleStateEvent) evt;
if (event.state() == IdleState.READER_IDLE) { // 读空闲
System.out.println("断开与客户端的连接, channel id=" + ctx.channel().id());
ctx.channel().close();
} else if (event.state() == IdleState.WRITER_IDLE) { // 写空闲
} else if (event.state() == IdleState.ALL_IDLE) { // 读写空闲
}
}
}
}定时发送心跳的类 HeartbeatThread
package com.sux.demo.websocket2;
import io.netty.channel.Channel;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.util.concurrent.GlobalEventExecutor;
public class HeartbeatThread extends Thread {
private ChannelGroup channelGroup;
private boolean running = true;
public HeartbeatThread(Channel channel) {
channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
channelGroup.add(channel);
}
public HeartbeatThread(ChannelGroup channelGroup) {
this.channelGroup = channelGroup;
}
@Override
public void run() {
while (running) {
try {
if (channelGroup.size() > 0) {
System.out.println("发送心跳");
for (Channel channel : channelGroup) {
channel.writeAndFlush(new PingWebSocketFrame());
}
}
Thread.sleep(2000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void close() {
running = false;
}
}服务端封装 WebSocketServer
package com.sux.demo.websocket2;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.timeout.IdleStateHandler;
import io.netty.util.CharsetUtil;
import java.util.concurrent.TimeUnit;
public class WebSocketServer {
private EventLoopGroup bossGroup;
private EventLoopGroup workerGroup;
private WebSocketServerHandler webSocketServerHandler;
public WebSocketServer() {
//创建两个线程组 boosGroup、workerGroup
bossGroup = new NioEventLoopGroup();
workerGroup = new NioEventLoopGroup();
webSocketServerHandler = new WebSocketServerHandler();
}
public void start(int port, String name) {
try {
//创建服务端的启动对象，设置参数
ServerBootstrap bootstrap = new ServerBootstrap();
//设置两个线程组boosGroup和workerGroup
bootstrap.group(bossGroup, workerGroup)
//设置服务端通道实现类型
.channel(NioServerSocketChannel.class)
//设置线程队列得到连接个数
.option(ChannelOption.SO_BACKLOG, 128)
//设置保持活动连接状态
.childOption(ChannelOption.SO_KEEPALIVE, true)
//使用匿名内部类的形式初始化通道对象
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
//给pipeline管道设置处理器
socketChannel.pipeline().addLast(new HttpServerCodec());
socketChannel.pipeline().addLast(new HttpObjectAggregator(65536));
socketChannel.pipeline().addLast(new WebSocketServerProtocolHandler("/websocket", null, false, 65536, false, false, false, 10000));
socketChannel.pipeline().addLast(new IdleStateHandler(5, 2, 0, TimeUnit.SECONDS));
socketChannel.pipeline().addLast(new ServerHeartbeatHandler());
socketChannel.pipeline().addLast(webSocketServerHandler);
}
});//给workerGroup的EventLoop对应的管道设置处理器
//绑定端口号，启动服务端
ChannelFuture channelFuture = bootstrap.bind(port).sync();
System.out.println(name + " 已启动");
// 定时发送心跳
startHeartbeat();
//对通道关闭进行监听
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
}
}
public void startHeartbeat() {
HeartbeatThread thread = new HeartbeatThread(webSocketServerHandler.getChannelGroup());
thread.start();
}
public void send(String text) {
for (Channel channel : webSocketServerHandler.getChannelGroup()) {
channel.writeAndFlush(new TextWebSocketFrame(Unpooled.copiedBuffer(text, CharsetUtil.UTF_8)));
}
}
public boolean hasClient() {
return webSocketServerHandler.getChannelGroup().size() > 0;
}
}说明：new IdleStateHandler(5, 2, 0, TimeUnit.SECONDS)第一个参数5表示读空闲时间间隔是5秒，第二个参数2表示写空闲的时间间隔是2秒，第3个参数0表示不检测读写空闲。在ServerHeartbeatHandler代码中，读写空闲时断开与客户端的连接。
服务端消息处理 WebSocketServerHandler
package com.sux.demo.websocket2;
import io.netty.channel.*;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.util.concurrent.GlobalEventExecutor;
@ChannelHandler.Sharable
public class WebSocketServerHandler extends SimpleChannelInboundHandler<Object> {
private ChannelGroup channelGroup;
public WebSocketServerHandler() {
channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
}
public ChannelGroup getChannelGroup() {
return channelGroup;
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) {
if (msg instanceof PongWebSocketFrame) {
System.out.println("收到客户端" + ctx.channel().remoteAddress() + "发来的心跳：PONG");
}
if (msg instanceof TextWebSocketFrame) {
TextWebSocketFrame frame = (TextWebSocketFrame) msg;
System.out.println("收到客户端" + ctx.channel().remoteAddress() + "发来的消息：" + frame.text());
/* // 测试转发消息
for (Channel channel : channelGroup) {
if (!ctx.channel().id().toString().equals(channel.id().toString())) {
channel.writeAndFlush(new TextWebSocketFrame(Unpooled.copiedBuffer(frame.text(), CharsetUtil.UTF_8)));
System.out.println("服务端向客户端 " + channel.id().toString() + " 转发消息：" + frame.text());
}
} */
}
}
@Override
public void channelActive(ChannelHandlerContext ctx) {
channelGroup.add(ctx.channel());
System.out.println("客户端" + ctx.channel().id().toString() + "已连接");
}
@Override
public void channelInactive(ChannelHandlerContext ctx) {
channelGroup.remove(ctx.channel());
System.out.println("客户端" + ctx.channel().id() + "已断开");
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) {
ctx.flush();
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
ctx.close();
}
}服务端测试主机 WebSocketServerHost
package com.sux.demo.websocket2;
public class WebSocketServerHost {
public static void main(String[] args) {
WebSocketServer webSocketServer = new WebSocketServer();
SendDataToClientThread thread = new SendDataToClientThread(webSocketServer);
thread.start();
webSocketServer.start(40005, "WebSocket服务端");
}
}
class SendDataToClientThread extends Thread {
private WebSocketServer webSocketServer;
private int index = 1;
public SendDataToClientThread(WebSocketServer webSocketServer) {
this.webSocketServer = webSocketServer;
}
@Override
public void run() {
try {
while (index <= 5) {
if (webSocketServer.hasClient()) {
String msg = "服务端发送的测试消息, index = " + index;
webSocketServer.send(msg);
index++;
}
Thread.sleep(1000);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}客户端
客户端心跳事件处理 ClientHeartbeatHandler
package com.sux.demo.websocket2;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
public class ClientHeartbeatHandler extends ChannelInboundHandlerAdapter {
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
if (evt instanceof IdleStateEvent) {
IdleStateEvent event = (IdleStateEvent) evt;
if (event.state() == IdleState.READER_IDLE) { // 读空闲
System.out.println("断开与服务端的连接");
ctx.channel().close();
} else if (event.state() == IdleState.WRITER_IDLE) { // 写空闲
} else if (event.state() == IdleState.ALL_IDLE) { // 读写空闲
}
}
}
}客户端封装 WebSocketClient
package com.sux.demo.websocket2;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshakerFactory;
import io.netty.handler.codec.http.websocketx.WebSocketClientProtocolHandler;
import io.netty.handler.codec.http.websocketx.WebSocketVersion;
import io.netty.handler.timeout.IdleStateHandler;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.concurrent.TimeUnit;
public class WebSocketClient {
private NioEventLoopGroup eventExecutors;
private Channel channel;
private HeartbeatThread heartbeatThread;
public WebSocketClient() {
eventExecutors = new NioEventLoopGroup();
}
public Channel getChannel() {
return channel;
}
public void connect(String ip, int port, String name) {
try {
WebSocketClientHandshaker handshaker = WebSocketClientHandshakerFactory.newHandshaker(
new URI("ws://" + ip + ":" + port + "/websocket"), WebSocketVersion.V13, null, false, new DefaultHttpHeaders());
WebSocketClientHandler handler = new WebSocketClientHandler(handshaker);
ClientHeartbeatHandler heartbeatHandler = new ClientHeartbeatHandler();
//创建bootstrap对象，配置参数
Bootstrap bootstrap = new Bootstrap();
//设置线程组
bootstrap.group(eventExecutors)
//设置客户端的通道实现类型
.channel(NioSocketChannel.class)
//使用匿名内部类初始化通道
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
//添加客户端通道的处理器
ch.pipeline().addLast(new HttpClientCodec());
ch.pipeline().addLast(new HttpObjectAggregator(65536));
ch.pipeline().addLast(new WebSocketClientProtocolHandler(handshaker, true, false));
ch.pipeline().addLast(new IdleStateHandler(5, 2, 0, TimeUnit.SECONDS));
ch.pipeline().addLast(heartbeatHandler);
ch.pipeline().addLast(handler);
}
});
// 连接服务端
ChannelFuture channelFuture = bootstrap.connect(ip, port);
// 在连接关闭后尝试重连
channelFuture.channel().closeFuture().addListener(future -> {
try {
if (heartbeatThread != null && heartbeatThread.isAlive()) {
System.out.println("停止发送心跳线程");
heartbeatThread.close();
}
Thread.sleep(2000);
System.out.println("重新连接服务端");
connect(ip, port, name); // 重新连接服务端
} catch (Exception e) {
e.printStackTrace();
}
});
channelFuture.sync();
channel = channelFuture.channel();
System.out.println(name + " 已启动");
// 定时发送心跳
heartbeatThread = new HeartbeatThread(channel);
heartbeatThread.start();
//对通道关闭进行监听
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
}
}
}说明：new IdleStateHandler(5, 2, 0, TimeUnit.SECONDS)第一个参数5表示读空闲时间间隔是5秒，第二个参数2表示写空闲的时间间隔是2秒，第3个参数0表示不检测读写空闲。在ClientHeartbeatHandler代码中，读写空闲时断开与服务端的连接。
客户端消息处理 WebSocketClientHandler
package com.sux.demo.websocket2;
import io.netty.channel.*;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.websocketx.*;
@ChannelHandler.Sharable
public class WebSocketClientHandler extends SimpleChannelInboundHandler<Object> {
private WebSocketClientHandshaker handshaker;
private ChannelPromise handshakeFuture;
public WebSocketClientHandler(WebSocketClientHandshaker handshaker) {
this.handshaker = handshaker;
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) {
if (!handshaker.isHandshakeComplete()) {
try {
handshaker.finishHandshake(ctx.channel(), (FullHttpResponse) msg);
handshakeFuture.setSuccess();
} catch (WebSocketHandshakeException e) {
handshakeFuture.setFailure(e);
}
return;
}
if (msg instanceof PongWebSocketFrame) {
System.out.println("收到服务端" + ctx.channel().remoteAddress() + "发来的心跳：PONG");
}
if (msg instanceof TextWebSocketFrame) {
TextWebSocketFrame frame = (TextWebSocketFrame) msg;
System.out.println("收到服务端" + ctx.channel().remoteAddress() + "发来的消息：" + frame.text()); // 接收服务端发送过来的消息
}
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) {
handshakeFuture = ctx.newPromise();
}
@Override
public void channelActive(ChannelHandlerContext ctx) {
}
@Override
public void channelInactive(ChannelHandlerContext ctx) {
System.out.println("客户端下线");
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) {
ctx.flush();
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
ctx.close();
}
}客户端测试主机 WebSocketClientHost
package com.sux.demo.websocket2;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.CharsetUtil;
public class WebSocketClientHost {
public static void main(String[] args) {
WebSocketClient webSocketClient = new WebSocketClient();
SendDataToServerThread thread = new SendDataToServerThread(webSocketClient);
thread.start();
webSocketClient.connect("127.0.0.1", 40005, "WebSocket客户端");
}
}
class SendDataToServerThread extends Thread {
private WebSocketClient webSocketClient;
private int index = 1;
public SendDataToServerThread(WebSocketClient webSocketClient) {
this.webSocketClient = webSocketClient;
}
@Override
public void run() {
try {
while (index <= 5) {
Channel channel = webSocketClient.getChannel();
if (channel != null && channel.isActive()) {
String msg = "客户端发送的测试消息, index = " + index;
channel.writeAndFlush(new TextWebSocketFrame(Unpooled.copiedBuffer(msg, CharsetUtil.UTF_8)));
index++;
}
Thread.sleep(1000);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}测试
测试一
步骤：先启动服务端，再启动客户端
现象：客户端与服务端互发消息，消息发完后，互发心跳
测试二
步骤：先启动服务端，再启动客户端，然后关闭服务端，过一会再启动服务端
现象：客户端断线重连，通信恢复，正常发消息和心跳
测试三
步骤：先启动客户端，过一会再启动服务端
现象：服务端启动后，客户端连上服务端，正常通信，互发消息，消息发完互发心跳
遇到的问题
1. 心跳问题
如果客户端想确认服务端是否在线，就向服务端发PING，如果服务端在线，服务端就会回一个PONG，客户端就能收到PONG，如果客户端长时间收不到服务端的消息，就会触发读空闲，然后断开与服务端的连接，触发断线重连。
如果服务端想确认客户端是否在线，就向客户端发PING，如果客户端在线，客户端就会回一个PONG，服务端就能收到PONG，如果服务端长时间收不到客户端的消息，就会触发读空闲，然后断开与客户端的连接。
WebSocketClientProtocolHandler和WebSocketServerProtocolHandler类都有一个dropPongFrames参数，默认为true，如果你在读空闲时写了断开连接的操作，要把dropPongFrames设置为false，这样才可以在消息处理handler中接收到PONG，否则即使对方回应了PONG，也会被丢弃掉，导致触发读空闲，导致连接被断开。
2. 如何发心跳
我在网上看到两种方式
方式一：
channel.writeAndFlush(new PingWebSocketFrame());方式二：
channel.writeAndFlush(new TextWebSocketFrame("PING"));方式一，对方收到心跳，会自动回一个PONG，需要把dropPongFrames设置为false才能收到对方回应的PONG。
方式二，对方收到心跳，需要手动回一个PONG，用TextWebSocketFrame包装，我方可以像收普通消息那样收到这个文本PONG。
3. 在写空闲时发心跳需要注意
如果我方一直向对方发业务数据，就不会触发写空闲，就不会发心跳，就收不到对方的回应PONG，如果对方又没有向我方发业务数据，就会触发我方的读空闲，如果在我方读空闲中写了断开逻辑，连接就会被主动断开，这种情况是错误的。所以本文的代码中，是在一个线程中一直定时发送PING，这样如果对方在线，也会一直定时回应PONG，只要对方在线就不会触发我方的读空闲，如果对方不在线，才会触发我方的读空闲。
