网络Socket编程UDP协议例子

服务端代码

 public class UDPChatServer {
     //通讯端口
     private Integer port=8000;
     //数据报文的通讯通道对象
     private DatagramChannel channel;
     //发送数据的最大大小
     private final Integer MAX_SIZE=1024;

     private Charset charset=Charset.forName("UTF-8");

     public UDPChatServer() throws IOException {
         //DatagramChannel本身的open方法返回一个DatagramChannel对象
         channel=DatagramChannel.open();
         //获取数据报的socket对象UDP 的socket
         DatagramSocket socket=channel.socket();
         //将socket对象绑定上本地的端口
         SocketAddress address=new InetSocketAddress(port);
         socket.bind(address);
         System.out.println("server started!");
     }
     private void service(){
         //初始化一个新的字节缓存对象容量为MAX_SIZE=1024 个字节。
         ByteBuffer receiveBuffer=ByteBuffer.allocate(MAX_SIZE);
         while (true){
               //将缓存中的数据清空
             receiveBuffer.clear();
             try {
                 //从渠道中获取固定大小的数据，获取client连接
                InetSocketAddress client= (InetSocketAddress) channel.receive(receiveBuffer);
                //客户端每次请求到receiveBuffer里
                 //设置buffer指针的下标0。这样就可以从buffer开头，对该buffer进行遍历（读取）了
                 receiveBuffer.flip();
                 //将字节数据转为字符串
                 String msg= charset.decode(receiveBuffer).toString();
                 System.out.println(String.format("new data :%s %s %s ",client.getAddress(),client.getPort(),msg));
                 //应答client 发送数据到通道中的客户端
                 channel.send(ByteBuffer.wrap(reply(msg).getBytes(charset)),client);
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
     }
     private String reply(String word){
         return "you said :"+word;
     }
     public static void main(String[] args) throws IOException {
             new UDPChatServer().service();
     }
 }

客户端代码:

 public class UDPChatClient {
     private Integer port=8000;
     private String host="localhost";
     //UDP socket
     private DatagramSocket socket;
     private InetAddress address;
     private Charset charset=Charset.forName("UTF-8");

     public UDPChatClient() throws IOException {
         socket=new DatagramSocket();
         //设置服务器的地址
         address=InetAddress.getByName(host);
         System.out.println("connection ok");
     }
     public static void main(String[] args) throws IOException {
         new UDPChatClient().say();
     }
     private void say() throws IOException {
         BufferedReader localreader=new BufferedReader(new InputStreamReader(System.in));

         String word;
         while ((word=localreader.readLine())!=null){
             // 将string转为byte数组 发送udp包
             byte[] data=word.getBytes(charset);
             //组装包指定ip和端口的数据包
             DatagramPacket outputPacket=new DatagramPacket(data,data.length,address,port);
             //发送
             socket.send(outputPacket);
             //接收udp包放到byte数组中
             DatagramPacket inputPacket=new DatagramPacket(new byte[1024],1024);
             socket.receive(inputPacket);
             //打印获取的数据
             System.out.println(new String(inputPacket.getData(),0,inputPacket.getLength(),charset));

             //客户端主动关闭
             if (word.equals("bye")){
                 socket.close();
                 break;
             }

         }
     }
 }