testdatagrampacket.java

本书是一本为Java学习者在基础内容学习结束后进行课程设计时提供参考的指导书

package apibook.c5.s1;

import java.net.*;
import java.io.*;

//测试DatagramPacket类
public class TestDatagramPacket {
  public TestDatagramPacket() {
  }
  public static String dgExchange(String msg, InetAddress dst, int port) {
      byte[] outbuf = msg.getBytes();
      byte[] inbuf = new byte[256];  // default size

      try {
          //发送datagram
          DatagramPacket request =
              new DatagramPacket(outbuf, outbuf.length, dst, port);
          DatagramSocket sock = new DatagramSocket();
          sock.send(request);

          //等待回应
          DatagramPacket reply = new DatagramPacket(inbuf, inbuf.length);
          sock.receive(reply);

          System.out.println(
              "Received packet from:" + reply.getAddress() +
              " port: " + reply.getPort() +
              " length: " + reply.getLength());

          sock.close();
          return (new String(reply.getData()));
      } catch (SocketException e) {
          e.printStackTrace();
      } catch (IOException e) {
          e.printStackTrace();
      }
      return (null);
  }

  public static void main(String[] args) {
    try {
        String msg = "\n";
        int port = 2121;
        InetAddress dst = InetAddress.getLocalHost();

        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
            if (args.length >= 2)
                msg = args[1];
            if (args.length == 3)
                dst = InetAddress.getByName(args[2]);
        }

        System.out.println(dgExchange(msg, dst, port));
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }
  }

}