编写异步客户端（基于CompletionHandler）

import java.io.IOException;/**时代Java公众号**/

import java.net.InetSocketAddress;

import java.net.StandardSocketOptions;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.channels.AsynchronousSocketChannel;

import java.nio.channels.CompletionHandler;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.util.Random;

import java.util.concurrent.ExecutionException;


public class Main {

  public static void main(String[] args) {

    try (AsynchronousSocketChannel asyncChannel = AsynchronousSocketChannel

        .open()) {

      if (asyncChannel.isOpen()) {

        asyncChannel.setOption(StandardSocketOptions.SO_RCVBUF, 128 * 1024);

        asyncChannel.setOption(StandardSocketOptions.SO_SNDBUF, 128 * 1024);

        asyncChannel.setOption(StandardSocketOptions.SO_KEEPALIVE, true);

        asyncChannel.connect(new InetSocketAddress("127.0.0.1", 5555), null,
        /*
         from nowjava 
        */

            new CompletionHandler<Void, Void>() {


              ByteBuffer helloBuffer = ByteBuffer.wrap("Hello !"

                  .getBytes());

              ByteBuffer buffer = ByteBuffer.allocateDirect(1024);

              ByteBuffer randomBuffer;

              Charset charset = Charset.defaultCharset();

              CharsetDecoder decoder = charset.newDecoder();


              @Override

              public void completed(Void result, Void attachment) {

                try {

                  System.out.println("Successfully connected at: "

                      + asyncChannel.getRemoteAddress());

                  asyncChannel.write(helloBuffer).get();

                  while (asyncChannel.read(buffer).get() != -1) {

                    buffer.flip();

                    CharBuffer charBuffer = decoder.decode(buffer);

                    System.out.println(charBuffer.toString());

                    if (buffer.hasRemaining()) {

                      buffer.compact();

                    } else {

                      buffer.clear();

                    }

                    asyncChannel.write(ByteBuffer.wrap("test".getBytes())).get();

                  }

                } catch (IOException | InterruptedException

                    | ExecutionException ex) {

                  System.err.println(ex);

                } finally {

                  try {

                    asyncChannel.close();

                  } catch (IOException ex) {

                    System.err.println(ex);

                  }

                }

              }


              @Override