JAVA基础知识之网络编程——-基于AIO的异步Socket通信

异步IO

下面摘子李刚的《疯狂JAVA讲义》

按照POSIX标准来划分IO，分为同步IO和异步IO。对于IO操作分为两步，1）程序发出IO请求。 2）完成实际的IO操作。

阻塞IO和非阻塞IO都是针对第一步来划分的，如果发出IO请求会阻塞线程，就是阻塞IO，否则就是非阻塞IO。

同步IO和非同步IO是针对第二步来说的，如果实际IO操作是由操作系统完成，再返回给程序，就是异步IO。

如果实际的IO需要程序本身去执行，会阻塞线程，就是同步IO。

JAVA7的NIO.2提供了异步的channel，从而使网络Socket的异步通信成为可能。

使用异步IO通信只需要三步，

调用open静态方法创建AsynchronousServerSocketChannel
调用AsynchronousServerSocketChannel的bind方法监听指定IP和端口
调用AsynchronousServerSocketChannel的accept方法接受连接请求

下面是一个简单例子，

服务器端

 1 package aio;
 2 
 3 import java.io.IOException;
 4 import java.net.InetSocketAddress;
 5 import java.nio.ByteBuffer;
 6 import java.nio.channels.AsynchronousServerSocketChannel;
 7 import java.nio.channels.AsynchronousSocketChannel;
 8 import java.util.concurrent.ExecutionException;
 9 import java.util.concurrent.Future;
10 
11 public class Server {
12     private static final int PORT = 3002;
13     public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
14         try {
15             AsynchronousServerSocketChannel serverChannel =  AsynchronousServerSocketChannel.open();
16             serverChannel.bind(new InetSocketAddress(PORT));
17             while (true) {
18                 Future<AsynchronousSocketChannel> future = serverChannel.accept();
19                 //获取连接成功之后的AsynchronousSocketChannel
20                 AsynchronousSocketChannel socketChannel = future.get();
21                 socketChannel.write(ByteBuffer.wrap("你好，这是AIO世界".getBytes("utf-8"))).get();
22             }
23         } catch(IOException e) {
24             e.printStackTrace();
25         }
26     }
27 }

客户端

 1 package aio;
 2 
 3 import java.io.IOException;
 4 import java.net.InetSocketAddress;
 5 import java.nio.ByteBuffer;
 6 import java.nio.channels.AsynchronousSocketChannel;
 7 import java.nio.charset.Charset;
 8 import java.util.concurrent.ExecutionException;
 9 
10 public class Client {
11     private static final int PORT = 3002;
12     public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
13         ByteBuffer buff = ByteBuffer.allocate(1024);
14         Charset utf = Charset.forName("utf-8");
15         try {
16             AsynchronousSocketChannel clientChannel = AsynchronousSocketChannel.open();
17             clientChannel.connect(new InetSocketAddress("127.0.0.1",PORT)).get();
18             buff.clear();
19             clientChannel.read(buff).get();
20             buff.flip();
21             String content = utf.decode(buff).toString();
22             System.out.println("服务器信息："+content);
23         } catch (IOException ex) {
24             ex.printStackTrace();
25         }
26     }
27 }