netty传递字符串（Clinet）_netty writeandflush发送字符串-优快云博客

本文链接：https://blog.youkuaiyun.com/erchouchou/article/details/88375890

本文通过实例代码介绍了Netty中如何建立客户端并发送字符串。配置了装配引导类，使用NioSocketChannel连接服务器，并自定义了继承自SimpleChannelInboundHandler的EchoClientHandler来处理接收到的响应。

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装配引导类：

bootstrap.group(eventLoopGroup)
           .channel(NioSocketChannel.class)
           .remoteAddress(new InetSocketAddress(host, port))
           .handler(new ChannelInitializer<SocketChannel>()

连接服务器：

ChannelFuture channelFuture = bootstrap.connect().sync();

Handler类继承：

SimpleChannelInboundHandler<ByteBuf>

EchoClient类：

package client;

import java.net.InetSocketAddress;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class EchoClient{
	private final String host;
	private final int port;
	public EchoClient(String host, int port) {
		this.host = host;
		this.port = port;
	}
	
	public void start() throws Exception{
		EventLoopGroup eventLoopGroup = null;
		try{
			//1.创建引导类
			Bootstrap bootstrap = new Bootstrap();
			//2.实例线程池
			eventLoopGroup = new NioEventLoopGroup();
			//装配引导类
			bootstrap.group(eventLoopGroup)
			.channel(NioSocketChannel.class)
			.remoteAddress(new InetSocketAddress(host, port))
			.handler(new ChannelInitializer<SocketChannel>() {

				@Override
				protected void initChannel(SocketChannel ch) throws Exception {
					ch.pipeline().addLast(new EchoClientHandler());
				}
			});
			ChannelFuture channelFuture = bootstrap.connect().sync();
			channelFuture.channel().closeFuture().sync();
		}finally {
			eventLoopGroup.shutdownGracefully().sync();
		}
	}
	public static void main(String[] args) throws Exception {
		new EchoClient("localhost", 20000).start();
	}
}

EchoClientHandler类：

package client;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
	// 客户端连接服务器后被调用
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		System.out.println("客户端连接服务器，开始发送数据");
		byte[] req = "hello，我是客户端".getBytes();
		ByteBuf firstMessage = Unpooled.buffer(req.length);//发送类
		firstMessage.writeBytes(req);
		ctx.writeAndFlush(firstMessage);
	}
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
    	System.out.println("client 读取server数据..");
		// 服务端返回消息后
		ByteBuf buf = (ByteBuf) msg;
		byte[] req = new byte[buf.readableBytes()];
		buf.readBytes(req);
		String body = new String(req, "UTF-8");
		System.out.println("服务端数据为 :" + body);
    	
    }

	// • 发生异常时被调用
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
			throws Exception {
		System.out.println("client exceptionCaught..");
		// 释放资源
		ctx.close();
	}
}