Java java.nio.channels.Selector用法及代碼示例

//Java Program to test  
//echo server using NIO Selector 
  
import java.io.IOException; 
import java.net.InetSocketAddress; 
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; 
import java.util.Set; 
  
//Driver class for NIOServer 
public class NIOServer {     
    
  //Main method 
  public static void main(String[] args) throws IOException { 
      
    // Create a new Selector         
    Selector selector = Selector.open();   
      
    // Create a ServerSocketChannel, bind it, and configure it as non-blocking         
    ServerSocketChannel serverChannel = ServerSocketChannel.open();         
    serverChannel.bind(new InetSocketAddress("localhost", 5454));         
    serverChannel.configureBlocking(false);         
      
    // Register the server socket channel with the Selector for accepting connections         
    serverChannel.register(selector, SelectionKey.OP_ACCEPT);         
    ByteBuffer buffer = ByteBuffer.allocate(256);         
    System.out.println("Server started and listening on port 5454...");         
    while (true) {             
        
      // Select ready channels using the Selector             
      selector.select();             
        
      // Get the set of selected keys             
      Set<SelectionKey> selectedKeys = selector.selectedKeys();             
      Iterator<SelectionKey> keyIterator = selectedKeys.iterator();   
        
      while (keyIterator.hasNext()) {  
          
        SelectionKey key = keyIterator.next();                 
        if (key.isAcceptable()) { 
            
          // Accept a new client connection                     
          ServerSocketChannel server = (ServerSocketChannel) key.channel();  
          SocketChannel clientChannel = server.accept();                 
          clientChannel.configureBlocking(false);                    
            
          // Register the client channel with the Selector for reading   
          clientChannel.register(selector, SelectionKey.OP_READ);                 
        }                 
        if (key.isReadable()) {                    
            
          // Read data from the client                     
          SocketChannel client = (SocketChannel) key.channel();                     
          buffer.clear();                     
          int bytesRead = client.read(buffer);                     
          if (bytesRead == -1) {                         
              
            // Client closed the connection                         
            key.cancel();                         
            client.close();                         
            continue;                     
          }                     
            
          buffer.flip();                     
          String receivedMessage = new String(buffer.array(), 0, bytesRead);  
            
          // Process the received message (e.g., echo it back to the client)  
          System.out.println("Received: " + receivedMessage);               
            
          // Prepare the buffer for writing and echo the received message back to the client  
          buffer.rewind();                     
          client.write(buffer);                 
        }                 
          
        // Remove the processed key from the set         
        keyIterator.remove();      
      }         
    }     
  } 
}

//Java Program to create a  
//echo client using NIO Selector 
  
import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.nio.ByteBuffer; 
import java.nio.channels.SocketChannel; 
  
  
//Driver class for NIOClient 
public class NIOClient {     
    
  //Main method 
  public static void main(String[] args) throws IOException {   
      
    // Create a socket channel and connect to the server      
    SocketChannel clientChannel = SocketChannel.open();      
    clientChannel.connect(new InetSocketAddress("localhost", 5454));   
    ByteBuffer buffer = ByteBuffer.allocate(256);      
    String message = "Hello, NIO Server!";  
      
    // Message to send to the server        
    buffer.clear();        
    buffer.put(message.getBytes());        
    buffer.flip();        
      
    // Send the message to the server        
    while (buffer.hasRemaining()) {            
      clientChannel.write(buffer);         
    }         
    buffer.clear();        
      
    // Read the server's response        
    clientChannel.read(buffer);         
    buffer.flip();         
      
    // Convert the response to a String and print it         
    String response = new String(buffer.array(), 0, buffer.limit());         
    System.out.println("Server Response: " + response);         
    clientChannel.close();     
  } 
}