NIO学习笔记(4)-简单echo实例

echo小例子 

服务端

 

import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.net.ServerSocket; 
import java.nio.ByteBuffer; 
import java.nio.channels.SelectionKey; 
import java.nio.channels.Selector; 
import java.nio.channels.ServerSocketChannel; 
import java.nio.channels.SocketChannel; 
import java.util.Iterator; 
 
 
public class Ex2Server { 
 
    /** 
     * @param args 
     * @throws IOException  
     */ 
    public static void main(String[] args) throws IOException { 
        //第一件事是创建一个 Selector 
        Selector selector = Selector.open(); 
         
        //要监听的每一个端口都需要有一个 ServerSocketChannel  
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); 
        serverSocketChannel.configureBlocking(false); 
 
        ServerSocket serverSocket = serverSocketChannel.socket(); 
        serverSocket.bind(new InetSocketAddress(12345));//绑定一个端口 
         
        //SelectionKey 代表这个通道在此 Selector 上的这个注册。 
        //当某个 Selector 通知您某个传入事件时，它是通过提供对应于该事件的 SelectionKey 来进行的。 
        //SelectionKey 还可以用于取消通道的注册。 
        SelectionKey selectionKey = serverSocketChannel.register( 
                selector, SelectionKey.OP_ACCEPT);//注册accept事件 
         
        int num = 0; 
        ByteBuffer buffer = ByteBuffer.allocate(1024); 
        while(true){ 
            //select方法会阻塞，直到至少有一个已注册的事件发生 
            num = selector.select(); 
             
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator(); 
            SelectionKey key = null; 
            while(iterator.hasNext()){ 
                 key = iterator.next(); 
                 if(key.isAcceptable()){//accept 
                     ServerSocketChannel channel = (ServerSocketChannel)key.channel(); 
                     //相当于从ServerSocket中accept一个socket 
                     SocketChannel socketChannel = channel.accept(); 
                     socketChannel.configureBlocking(false);//设为非阻塞 
                     socketChannel.register(selector, SelectionKey.OP_READ); 
                      
                 }else if(key.isReadable()){ 
                     SocketChannel channel = (SocketChannel)key.channel(); 
                     int readNum = 0; 
                     while(readNum != -1){ 
                         buffer.clear(); 
                         channel.read(buffer);//读出 
                          
                         buffer.flip(); 
                         channel.write(buffer); 
                     } 
                     //channel.close(); 
                      
                 }else if(key.isWritable()){ 
                      
                 } 
                 iterator.remove(); 
            } 
        } 
         
    } 
 
} 

客户端

 

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.OutputStreamWriter; 
import java.io.PrintWriter; 
import java.net.InetSocketAddress; 
import java.net.Socket; 
import java.net.SocketAddress; 
 
 
public class Ex2Client { 
 
    /** 
     * @param args 
     * @throws IOException  
     */ 
    public static void main(String[] args) throws IOException { 
        SocketAddress address = new InetSocketAddress("localhost", 12345); 
        Socket s = new Socket(); 
        s.connect(address); 
        PrintWriter writer = new PrintWriter( new OutputStreamWriter(s.getOutputStream())); 
        writer.println("abc"); 
        writer.flush(); 
         
        BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream())); 
        System.out.println(reader.readLine()); 
         
        writer.close(); 
        reader.close(); 
        s.close(); 
    } 
 
} 

   如果写入的内容比较多，可以把读跟写分开

 

import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.net.ServerSocket; 
import java.nio.ByteBuffer; 
import java.nio.channels.SelectionKey; 
import java.nio.channels.Selector; 
import java.nio.channels.ServerSocketChannel; 
import java.nio.channels.SocketChannel; 
import java.util.Iterator; 
 
 
public class Ex2Server2 { 
 
    /** 
     * @param args 
     * @throws IOException  
     */ 
    public static void main(String[] args) throws IOException { 
        //第一件事是创建一个 Selector 
        Selector selector = Selector.open(); 
         
        //要监听的每一个端口都需要有一个 ServerSocketChannel  
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); 
        serverSocketChannel.configureBlocking(false); 
 
        ServerSocket serverSocket = serverSocketChannel.socket(); 
        serverSocket.bind(new InetSocketAddress(12345));//绑定一个端口 
         
        //SelectionKey 代表这个通道在此 Selector 上的这个注册。 
        //当某个 Selector 通知您某个传入事件时，它是通过提供对应于该事件的 SelectionKey 来进行的。 
        //SelectionKey 还可以用于取消通道的注册。 
        SelectionKey selectionKey = serverSocketChannel.register( 
                selector, SelectionKey.OP_ACCEPT);//注册accept事件 
         
        int num = 0; 
        ByteBuffer buffer = ByteBuffer.allocate(1024); 
        while(true){ 
            //select方法会阻塞，直到至少有一个已注册的事件发生 
            num = selector.select(); 
             
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator(); 
            SelectionKey key = null; 
            while(iterator.hasNext()){ 
                 key = iterator.next(); 
                 if(key.isAcceptable()){//accept 
                     ServerSocketChannel channel = (ServerSocketChannel)key.channel(); 
                     //相当于从ServerSocket中accept一个socket 
                     SocketChannel socketChannel = channel.accept(); 
                     socketChannel.configureBlocking(false);//设为非阻塞 
                     socketChannel.register(selector, SelectionKey.OP_READ); 
                      
                 }else if(key.isReadable()){ 
                     SocketChannel channel = (SocketChannel)key.channel(); 
                     int readNum = 1; 
                     while(readNum > 0){ 
                         buffer.clear(); 
                         readNum = channel.read(buffer);//读出 
                          
                         buffer.flip(); 
                         //channel.write(buffer); 
                     } 
                     channel.register(selector, SelectionKey.OP_WRITE); 
                     //channel.close(); 
                      
                 }else if(key.isWritable()){ 
                     SocketChannel channel = (SocketChannel)key.channel(); 
                     buffer.clear(); 
                     buffer.put("测试\r\n".getBytes()); 
                     buffer.flip(); 
                     channel.write(buffer);
 
                    //取消写入key的注册，不然一直可写 
                     key.cancel(); 
//改正：key.cancel会把channel也关闭，这里设置OPS为读，也就把写给反注册掉了
key.interestOps(SelectionKey.OP_READ);
                 } 
                 iterator.remove(); 
            } 
        } 
 
    } 
 
}