Netty的简单使用，实现socket通讯

import android.util.Log;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
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.NioSocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;

/**
 * @author 海晨忆
 * @date 2018/2/6
 * @desc
 */
public class SocketTcp {
  private static SocketTcp socketTcp = new SocketTcp();
  private Channel channel = null;
  private EventLoopGroup group;
  private int port;
  private String host;

  public static SocketTcp getInstance() {
    return socketTcp;
  }

  public SocketTcp setPort(int port) {
    this.port = port;
    return this;
  }

  public SocketTcp setHost(String host) {
    this.host = host;
    return this;
  }

  public void connect() {
    if (channel != null) return;
    if (group == null) {
      //NIO线程组
      group = new NioEventLoopGroup();
    }
    try {//配置Bootstrap
      Bootstrap bootstrap = new Bootstrap();
      bootstrap.group(group)
          .channel(NioSocketChannel.class)
          .option(ChannelOption.TCP_NODELAY, true)
          .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
              //以换行符为结束标记
              ChannelPipeline pipeline = ch.pipeline();
              pipeline.addLast("encoder", new StringEncoder(CharsetUtil.UTF_8));
              pipeline.addLast(new LineBasedFrameDecoder(Integer.MAX_VALUE));
              pipeline.addLast(new StringDecoder());
              pipeline.addLast(new MyHeartSocket());

              //以"$_"作为分隔符
              /*ChannelPipeline pipeline = ch.pipeline();
              pipeline.addLast("encoder", new StringEncoder(CharsetUtil.UTF_8));
              String s = "$_";
              ByteBuf byteBuf = Unpooled.copiedBuffer(s.getBytes());
              pipeline.addLast(new DelimiterBasedFrameDecoder(Integer.MAX_VALUE,byteBuf));
              pipeline.addLast(new StringDecoder());
              pipeline.addLast(new MyHeartSocket());*/

            }
          });
      //发起异步连接操作
      ChannelFuture channelFuture = bootstrap.connect(host, port).sync();
      channel = channelFuture.channel();
      //等待服务端监听端口关闭
      channel.closeFuture().sync();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      disConnect();
    }
  }

  /**
   * 断开tcp连接.
   */
  private void disConnect() {
    if (null != group) {
      group.shutdownGracefully();
    }
    group = null;
    channel = null;
  }

  public void sendMessage(String msg) {//连接成功后，通过Channel提供的接口进行IO操作
    try {
      if (channel != null && channel.isOpen()) {
        channel.writeAndFlush(msg).sync();
        Log.d("wz", "send succeed " + msg);
      } else {
        reConnect();
        throw new Exception("channel is null | closed");
      }
    } catch (Exception e) {
      reConnect();
      e.printStackTrace();
    }
  }

  /**
   * 重连.
   */
  private void reConnect() {
    new Thread(this::connect);
  }
}

package com.example.zwang.myapplication.socket;

import android.os.SystemClock;
import android.util.Log;

import java.util.concurrent.TimeUnit;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.EventLoop;
import io.netty.channel.SimpleChannelInboundHandler;


public class MyHeartSocket extends SimpleChannelInboundHandler<Object> {
  private ChannelHandlerContext ctx;
  private boolean isConnect = false;

  @Override
  protected void messageReceived(ChannelHandlerContext ctx, Object msg) throws Exception {
    Log.v("WZ", "连接正常messageReceived");
    ByteBuf msg1 = (ByteBuf) msg;
    byte[] bytes = new byte[msg1.readableBytes()];
    msg1.readBytes(bytes);
    String s = new String(bytes, "UTF-8");
    Log.v("WZ", "接收到的消息:" + s);
  }

  @Override
  public void channelActive(ChannelHandlerContext ctx) throws Exception {
    super.channelActive(ctx);
    Log.v("WZ", "连接正常channelActive");
    isConnect = true;
    if (this.ctx == null) {
      synchronized (MyHeartSocket.class) {
        if (this.ctx == null) {
          this.ctx = ctx;
          MyAppHeart();
        }
      }
    }
  }

  private void MyAppHeart() {
    new Thread(() -> {
      while (ctx != null && isConnect) {
        String data = "123";
        byte[] bytes = data.getBytes();
        if (isConnect) {
          ctx.writeAndFlush(Unpooled.buffer(bytes.length).writeBytes(bytes));
          SystemClock.sleep(3000);
        }
      }
    }).start();
  }

  @Override
  public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    EventLoop loop = ctx.channel().eventLoop();
    loop.schedule(() -> SocketTcp.getInstance().connect(), 5, TimeUnit.SECONDS);
    super.channelInactive(ctx);
    Log.v("WZ", "重新连接socket服务器");
    isConnect = false;
  }

  @Override
  public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
    super.userEventTriggered(ctx, evt);
    Log.v("WZ", "发送数据包");
  }

  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    super.exceptionCaught(ctx, cause);
    Log.v("WZ", "连接出现异常");
    this.ctx.close();
    this.ctx = null;
  }
}