Netty中客户端如何连接服务端

<dependency>
  <groupId>io.netty</groupId>
  <artifactId>netty-all</artifactId>
  <version>4.1.43.Final</version>
</dependency>

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.net.InetSocketAddress;

public class Client {

    public static void main(String[] args) {
        EventLoopGroup group = new NioEventLoopGroup();
        EventLoopGroup businessGroup = new NioEventLoopGroup(8);
        Bootstrap bootstrap = new Bootstrap();

        bootstrap.group(group)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) {
                        ChannelPipeline channelPipeline = ch.pipeline();
                        channelPipeline.addLast(new StringDecoder());
                        channelPipeline.addLast(new StringEncoder());
                        channelPipeline.addLast(businessGroup, new ClientHandler());
                    }
                });

        bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
        bootstrap.option(ChannelOption.TCP_NODELAY, true);
        // 连接服务端
        bootstrap.connect(new InetSocketAddress("127.0.0.1", 8080));

    }
}

服务端主线流程: 1.创建Channel   2.初始化Channel   3.注册Channel    4.绑定端口

public ChannelFuture connect(SocketAddress remoteAddress) {
  return doResolveAndConnect(remoteAddress, config.localAddress());
}

private ChannelFuture doResolveAndConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
  // 创建 初始化 注册
  final ChannelFuture regFuture = initAndRegister();
  final Channel channel = regFuture.channel();

  if (regFuture.isDone()) {
    if (!regFuture.isSuccess()) {
      return regFuture;
    }
    return doResolveAndConnect0(channel, remoteAddress, localAddress, channel.newPromise());
  } else {
    final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
    regFuture.addListener(new ChannelFutureListener() {
      @Override
      public void operationComplete(ChannelFuture future) throws Exception {
        Throwable cause = future.cause();
        if (cause != null) {
          promise.setFailure(cause);
        } else {
          promise.registered();
          // 连接
          doResolveAndConnect0(channel, remoteAddress, localAddress, promise);
        }
      }
    });
    return promise;
  }
}

final ChannelFuture initAndRegister() {
  Channel channel = null;
  try {
    // 创建
    channel = channelFactory.newChannel();
    // 初始化
    init(channel);
  } catch (Throwable t) {
    if (channel != null) {
      channel.unsafe().closeForcibly();
      return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
    }
    return new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE).setFailure(t);
  }

  // 注册
  ChannelFuture regFuture = config().group().register(channel);
  if (regFuture.cause() != null) {
    if (channel.isRegistered()) {
      channel.close();
    } else {
      channel.unsafe().closeForcibly();
    }
  }

  return regFuture;
}

// 代码位置
io.netty.bootstrap.ServerBootstrap.ServerBootstrapAcceptor#channelRead