Java Ping Client

PingClient.java

/**
 * Ping Client
 * @author nieyong
 */
package com.learn;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
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 java.util.concurrent.TimeUnit;

class PingClientHandler extends ChannelInboundHandlerAdapter {
	private final ByteBuf firstMessage;

	public PingClientHandler() {
		firstMessage = PooledByteBufAllocator.DEFAULT.buffer(22);

		// weixin 16 byte's header
		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(16);

		firstMessage.writeByte(0);
		firstMessage.writeByte(16);

		firstMessage.writeByte(0);
		firstMessage.writeByte(1);

		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(6);

		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(0);
		firstMessage.writeByte(1);

		// just for /n
		firstMessage.writeByte('\n'); // 1 byte

		// footer 16 byte
		String welcome = "hello"; // 5 byte
		firstMessage.writeBytes(welcome.getBytes());
	}

	@Override
	public void channelActive(ChannelHandlerContext ctx) {
		ctx.writeAndFlush(firstMessage);
	}

	@Override
	public void channelRead(final ChannelHandlerContext ctx, final Object msg)
			throws Exception {
		ctx.executor().schedule(new Runnable() {
			@Override
			public void run() {
				ctx.channel().writeAndFlush(msg);
			}
		}, 1, TimeUnit.SECONDS);
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		ctx.flush();
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
		System.err.println("Unexpected exception from downstream :"
				+ cause.getMessage());
		ctx.close();
	}
}

public class PingClient {

	private final String host;
	private final int port;

	public PingClient(String host, int port) {
		this.host = host;
		this.port = port;
	}

	public void run() throws Exception {
		EventLoopGroup group = new NioEventLoopGroup();
		try {
			Bootstrap b = new Bootstrap();
			b.group(group).channel(NioSocketChannel.class)
					.option(ChannelOption.TCP_NODELAY, true)
					.handler(new ChannelInitializer<SocketChannel>() {
						@Override
						public void initChannel(SocketChannel ch)
								throws Exception {
							ch.pipeline().addLast(new PingClientHandler());
						}
					});

			ChannelFuture f = b.connect(host, port).sync();

			f.channel().closeFuture().sync();
		} finally {
			// Shut down the event loop to terminate all threads.
			group.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws Exception {
		String host = "127.0.0.1";
		int port = 8080;

		if (args.length == 3) {
			host = args[0];
			port = Integer.parseInt(args[1]);
		}

		new PingClient(host, port).run();
	}
}