通信框架netty5.0教程二：netty超时心跳机制

上一章已经讲了如何搭建一个简单的netty server，这一章讲一下netty超时心跳机制。

一般应用场景是client在一定时间未收到server端数据时给server端发送心跳请求，server收到心跳请求后发送一个心跳包给client端，以此维持通信。

发送心跳由client执行，server端反馈心跳就可以了，好了不多说了，上代码：

netty server代码：

import java.util.concurrent.TimeUnit;

import org.apache.log4j.Logger;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.timeout.IdleStateHandler;

public class NettyServerBootstrap {

	private static Logger logger = Logger.getLogger(NettyServerBootstrap.class);

	private int port;

	public NettyServerBootstrap(int port) {
		this.port = port;
		bind();
	}

	private void bind() {

		EventLoopGroup boss = new NioEventLoopGroup();
		EventLoopGroup worker = new NioEventLoopGroup();

		try {

			ServerBootstrap bootstrap = new ServerBootstrap();

			bootstrap.group(boss, worker);
			bootstrap.channel(NioServerSocketChannel.class);
			bootstrap.option(ChannelOption.SO_BACKLOG, 1024);
			bootstrap.option(ChannelOption.TCP_NODELAY, true);
			bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);
			bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
				@Override
				protected void initChannel(SocketChannel socketChannel)
						throws Exception {
					ChannelPipeline p = socketChannel.pipeline();

					// 超时处理：参数分别为读超时时间、写超时时间、读和写都超时时间、时间单位
					p.addLast(new IdleStateHandler(15, 30, 30, TimeUnit.SECONDS));
					p.addLast(new NettyIdleStateHandler());

					p.addLast(new NettyServerHandler());
				}
			});
			ChannelFuture f = bootstrap.bind(port).sync();
			if (f.isSuccess()) {
				logger.debug("启动Netty服务成功，端口号：" + this.port);
			}
			// 关闭连接
			f.channel().closeFuture().sync();

		} catch (Exception e) {
			logger.error("启动Netty服务异常，异常信息：" + e.getMessage());
			e.printStackTrace();
		} finally {
			boss.shutdownGracefully();
			worker.shutdownGracefully();
		}
	}

}

server端NettyIdleStateHandler：

import org.apache.log4j.Logger;

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;

/**
 * 处理超时连接handler
 * 
 * @author Guo Kaixuan
 *
 */
public class NettyIdleStateHandler extends ChannelHandlerAdapter {

	private static Logger logger = Logger
			.getLogger(NettyIdleStateHandler.class);
	
	@Override
	public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
			throws Exception {

		if (evt instanceof IdleStateEvent) {

			IdleStateEvent event = (IdleStateEvent) evt;

			if (event.state().equals(IdleState.READER_IDLE)) {

				logger.warn("Netty服务器在通道" + ctx.channel().id() + "上读超时，已将该通道关闭");

			} else if (event.state().equals(IdleState.WRITER_IDLE)) {
				
				logger.warn("Netty服务器在通道" + ctx.channel().id() + "上写超时，已将该通道关闭");
				
			} else if (event.state().equals(IdleState.ALL_IDLE)) {

				logger.warn("Netty服务器在通道" + ctx.channel().id()
						+ "上读&写超时，已将该通道关闭");
			}

			super.userEventTriggered(ctx, evt);
		}
	}

}

server端NettyServerHandler

import java.io.UnsupportedEncodingException;

import org.apache.log4j.Logger;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.socket.SocketChannel;

public class NettyServerHandler extends ChannelHandlerAdapter {

	private static Logger logger = Logger.getLogger(NettyServerHandler.class);
	
	@Override
	public void channelInactive(ChannelHandlerContext ctx) throws Exception {
		super.channelInactive(ctx);
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) {
		
		ByteBuf buf = (ByteBuf) msg;

		String recieved = getMessage(buf);  
		System.out.println("服务器接收到消息：" + recieved);

		try {		
			ctx.writeAndFlush(newPing("服务器已收到心跳包"));	
			
		} catch (Exception e) {
			ServiceLoggerUtils.error("通信异常");
			return;
		}
	}

	/*
	 * 从ByteBuf中获取信息 使用UTF-8编码返回
	 */
	private String getMessage(ByteBuf buf) {

		byte[] con = new byte[buf.readableBytes()];
		buf.readBytes(con);
		try {
			return new String(con, Constant.UTF8);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}
	}

	public static ByteBuf newPing(String message) {

		byte[] mes = message.getBytes();
		ByteBuf pingMessage = Unpooled.buffer();
		pingMessage.writeBytes(mes);

		return pingMessage;
	}
	
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
			throws Exception {
	}
}

client端代码：

import java.util.concurrent.TimeUnit;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.timeout.IdleStateHandler;

public class NettyClientBootstrap {

	/*
	 * 服务器端口号
	 */
	private int port;

	/*
	 * 服务器IP
	 */
	private String host;

	@SuppressWarnings("unused")
	private SocketChannel socketChannel;
	
	public NettyClientBootstrap(int port, String host)
			throws InterruptedException {
		this.port = port;
		this.host = host;
		start();
	}

	private void start() throws InterruptedException {
		
		EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
		
		try {
			
			Bootstrap bootstrap = new Bootstrap();
			bootstrap.channel(NioSocketChannel.class);
			bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
			bootstrap.group(eventLoopGroup);
			bootstrap.remoteAddress(host, port);
			bootstrap.handler(new ChannelInitializer<SocketChannel>() {
				@Override
				protected void initChannel(SocketChannel socketChannel)
						throws Exception {
					
					//超时处理：参数分别为读超时时间、写超时时间、读和写都超时时间、时间单位
					socketChannel.pipeline().addLast(new IdleStateHandler(3, 8, 0, TimeUnit.SECONDS));
					socketChannel.pipeline().addLast(new NettyIdleStateHandler());
					
					socketChannel.pipeline().addLast(new NettyClientHandler());
				}
			});
			ChannelFuture future = bootstrap.connect(host, port).sync();
			if (future.isSuccess()) {
				socketChannel = (SocketChannel) future.channel();
				System.out.println("----------------connect server success----------------");
			}
			future.channel().closeFuture().sync();
		} finally {
			eventLoopGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws InterruptedException {
		
		NettyClientBootstrap bootstrap = new NettyClientBootstrap(9999,
				"localhost");

	}
}

client端NettyIdleStateHandler：

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;

/**
 * 处理超时连接handler
 * 
 * @author
 *
 */
public class NettyIdleStateHandler extends ChannelHandlerAdapter {

	@Override
	public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
			throws Exception {

		if (evt instanceof IdleStateEvent) {

			IdleStateEvent event = (IdleStateEvent) evt;

			if (event.state().equals(IdleState.READER_IDLE)) {

				String message = "心跳包";

				byte[] req = message.getBytes();
				ByteBuf pingMessage = Unpooled.buffer();
				pingMessage.writeBytes(req);
				
				ctx.writeAndFlush(pingMessage);
				System.out.println("客户端读超时，已发送心跳");

			} else if (event.state().equals(IdleState.WRITER_IDLE)) {
				System.out.println("客户端写超时");
			} else if (event.state().equals(IdleState.ALL_IDLE)) {
				System.out.println("客户端读&写超时");
			}

			super.userEventTriggered(ctx, evt);
		}
	}
}

client端NettyClientHandler：

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class NettyClientHandler extends ChannelHandlerAdapter  {
    
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
	
	String result = getMessage((ByteBuf) msg);
	System.out.print("客户端收到服务器响应数据:" + result);
         
    }

    private String getMessage(ByteBuf buf) {

		byte[] con = new byte[buf.readableBytes()];
		buf.readBytes(con);
		try {
			return new String(con, Constant.UTF8);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}
	}
}

以上代码需要引入netty5包和log4j包，netty包上一张有将如何加入，log4j请自行下载或者maven添加。如有问题欢迎留言。