java netty 伺服器簡單例子
例子實現的功能是客戶端連線伺服器，伺服器返回當前時間的例子，使用maven匯入netty的包，其pom依賴為：

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.17.Final</version>
</dependency>

處理網路資料的程式如下：

import io.netty.buffer.ByteBuf;
import
 
 io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.io.UnsupportedEncodingException;

public class TimeServerHandler extends ChannelInboundHandlerAdapter {

    //有連線可以讀取
    @Override
    public void channelRead(ChannelHandlerContext ctx,Object msg){
        ByteBuf buf = (ByteBuf)msg;
        byte
 
[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        try {
            String body = new String(req,"UTF-8");
            System.out.println("The time server receive order :" + body);
            String currentTime = System.currentTimeMillis()+"";
            ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
            ctx.write(resp);
        } catch
 
 (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }

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

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx,Throwable cause){
        System.out.println(cause.toString());
        ctx.close();
    }
}

伺服器初始化的程式如下：

import io.netty.bootstrap.ServerBootstrap;
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.NioServerSocketChannel;

public class TimeServer {
    public void bind(int port) throws Exception {

        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workGroup = new NioEventLoopGroup();
        try{
        ServerBootstrap b = new ServerBootstrap();
        /*最大連線數量設定 BACKLOG用於構造服務端套接字ServerSocket物件，標識當伺服器請求處理執行緒全滿時，用於臨時存放已完成三次握手的請求的佇列的最大長度。如果未設定或所設定的值小於1，Java將使用預設值50。*/
        b.group(bossGroup,workGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG,1024).childHandler(new ChildChannelHandler());
        //繫結埠，等待同步成功
        ChannelFuture f = b.bind(port).sync();
        f.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }

    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {

        protected void initChannel(SocketChannel socketChannel) throws Exception {
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }
    }

    public static void main(String[] args){
        int port = 9000;
        try {
            new TimeServer().bind(port);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

使用網路助手進行除錯，結果如下：