轉自 http://blog.csdn.net/alangdangjia/article/details/9065845

1. import java.io.BufferedReader;  
2.  import java.io.ByteArrayInputStream;  
3.  import java.io.DataInputStream;  
4.  import java.io.IOException;  
5.  import java.io.InputStreamReader;  
6.  import java.net.DatagramSocket;  
7.  import java.net.InetSocketAddress;  
8.  import java.nio.ByteBuffer;  
9.  import java.nio.channels.DatagramChannel;  
10.  import java.nio.channels.SelectionKey;  
11.  import java.nio.channels.Selector;  
12.  import java.util.Set;  
13.  publicclass NioUdpServer {  
14.      publicstaticvoid main(String[] args) {  
15.          try {  
16.              Selector selector = Selector.open();  
17.              DatagramChannel channel = DatagramChannel.open();  
18.              channel.configureBlocking(false);  
19.              DatagramSocket socket = channel.socket();  
20.              socket.bind(new InetSocketAddress(1000));  
21.              channel.register(selector, SelectionKey.OP_READ);  
22.             ByteBuffer receiveBuffer = ByteBuffer.allocate(1024
    );  
23.              finalint PACKAGE_SIZE = 10;  
24.              while(true){  
25.                  int n = selector.select();  
26.                  if(n == 0){  
27.                      continue;  
28.                  }  
29.                  Set<SelectionKey> readyKeys = selector.selectedKeys();  
30.                  for(SelectionKey key : readyKeys){  
31.                      readyKeys.remove(key);  
32.                     if(key.isReadable()){  
33.                          DatagramChannel dc = (DatagramChannel)key.channel();  
34.                          InetSocketAddress client = (InetSocketAddress)dc.receive(receiveBuffer); //接收來自任意一個Client的資料報
35.                          key.interestOps(SelectionKey.OP_READ);  
36.                         System.out.println("client ----> IP: " + client.getAddress().getHostAddress() + ", port: " + client.getPort());  
37.                          System.out.println("receiveBuffer.position() = " + receiveBuffer.position());  
38.                          if(receiveBuffer.position() >= PACKAGE_SIZE){  
39.                              receiveBuffer.flip();  
40.                              DataInputStream dis = new DataInputStream(new ByteArrayInputStream(receiveBuffer.array()));  
41.                              System.out.println(dis.readInt());  
42.                              BufferedReader d = new BufferedReader(new InputStreamReader(dis));  
43.                              System.out.println(d.readLine());  
44.                             receiveBuffer.clear();  
45.                          }else{  
46.                              dc.register(selector, SelectionKey.OP_READ);  
47.                          }  
48.                      }//if
49.                  }  
50.              }//while
51.          } catch (IOException e) {  
52.              e.printStackTrace();  
53.          }  
54.      }  
55.  }  

2. 客戶端

1. import java.net.DatagramPacket;  
2. import java.net.DatagramSocket;  
3. import java.net.InetAddress;  
4. import java.net.UnknownHostException;  
5. publicclass NioUdpClient extends Thread {  
6.     privatebyte[] sendData;  
7.     private InetAddress serverAddr;  
8.     privateint port;  
9.     privateint dataLen;  
10.     public NioUdpClient(InetAddress ip, int port, byte[] str,int len) {  
11.         this.serverAddr = ip;  
12.         this.sendData = str;  
13.         this.dataLen = len;  
14.         this.port = port;  
15.     }  
16.     publicstaticvoid main(String[] args) {  
17. //      //測試字串
18.         byte[] bys = newbyte[256];  
19.         for(int i = 0; i < 256; i++){  
20.             bys[i] = (byte) i;  
21.         }  
22.         for(int i = 0; i < bys.length; i++){  
23.             System.out.println(i + "--->" + bys[i]);  
24.         }  
25.         while(true){  
26.             try {  
27.                 new Thread(new NioUdpClient(InetAddress.getLocalHost(), 1000, bys,256)).start();  
28.             } catch (UnknownHostException e) {  
29.                 // TODO Auto-generated catch block
30.                 e.printStackTrace();  
31.             }  
32.             Thread.currentThread();  
33.             try {  
34.                 Thread.sleep(200);  
35.             } catch (InterruptedException e) {  
36.                 // TODO Auto-generated catch block
37.                 e.printStackTrace();  
38.             }  
39.         }  
40.     }  
41.     publicvoid run() {  
42.         try {  
43.             System.out.println("Client: Start connecting\n");  
44.             DatagramSocket socket = new DatagramSocket();  
45.             DatagramPacket packet = new DatagramPacket(sendData, dataLen, serverAddr, port);  
46.             System.out.println("Client: Sending "+dataLen+"bytes'" + new String(sendData) + "'\n");  
47.             socket.send(packet);  
48.             System.out.println("Client: Message sent\n");  
49.             System.out.println("Client: Succeed!\n");  
50.         } catch (Exception e) {  
51.             System.out.println("Client: Error!\n");  
52.         }  
53.     }  
54. }