Netty框架学习(三) - 应答服务器与客户端

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前言

挺长的一段时间没写博客了，自己也是有点偷懒了，现在将之前所学的慢慢再记录下来也不迟。上一篇关于Netty的文章里面所写的只是最简单的Netty服务器与客户端，做的只是启动连接，并打印消息而已，服务器与客户端之间并没有进行相互的通信。而这一篇文章则要演示的是服务器与客户端相互通信的例子。

EchoServer服务器

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/**
 * 响应服务器
 */
public class EchoServer {
	private int port;

	public EchoServer(int port) {
		this.port = port;
	}

	public void start() throws Exception {
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();

		try {
			ServerBootstrap b = new ServerBootstrap();
			b.group(bossGroup, workerGroup)
					.channel(NioServerSocketChannel.class)
					.childHandler(new ChannelInitializer<SocketChannel>() {
						@Override
						protected void initChannel(SocketChannel ch)
								throws Exception {
							ch.pipeline().addLast(new EchoServerHandler());
						}
					});
			ChannelFuture f = b.bind(port).sync();
			System.out.println(EchoServer.class + " started and listen on " + f.channel().localAddress());
			f.channel().closeFuture().sync();
		} finally {
			workerGroup.shutdownGracefully();
			bossGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws Exception {
		new EchoServer(5000).start();
	}
}
``` 

**EchoServer服务器处理程序**
```java
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg)
			throws Exception {
		ByteBuf buff = (ByteBuf) msg;
		System.out.println("server received: " + buff.toString(CharsetUtil.UTF_8));
		ctx.write(Unpooled.copiedBuffer("Hi, EchoClient!", CharsetUtil.UTF_8));
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		// 给ChannelFuture加上关闭的监听器
		ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
			throws Exception {
		cause.printStackTrace();
		ctx.close();
	}
}
``` 

**EchoClient客户端**
```java
/**
 * 响应客户端
 */
public class EchoClient {
	private String host;
	private int port;
	
	public EchoClient(String host, int port) {
		this.host = host;
		this.port = port;
	}

	public void start() throws Exception {
		EventLoopGroup group = new NioEventLoopGroup();

		try {
			Bootstrap b = new Bootstrap();
			b.group(group).channel(NioSocketChannel.class)
					.handler(new ChannelInitializer<SocketChannel>() {
						@Override
						protected void initChannel(SocketChannel ch)
								throws Exception {
							ch.pipeline().addLast(new EchoClientHandler());
						}
					});
			ChannelFuture f = b.connect(host, port).sync();
			f.channel().closeFuture().sync();
		} finally {
			group.shutdownGracefully();
		}
	}
	
	public static void main(String[] args) throws Exception {
		new EchoClient("127.0.0.1", 5000).start();
	}
}
``` 

**EchoClient客户端处理程序**
```java
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		ctx.writeAndFlush(Unpooled.copiedBuffer("Hello, EchoServer~!", CharsetUtil.UTF_8));
	}

	@Override
	protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg)
			throws Exception {
		System.out.println("client received: " + msg.toString(CharsetUtil.UTF_8));
	}
	
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
			throws Exception {
		cause.printStackTrace();
		ctx.close();
	}
}