package datagrams;import java.io.*;import java.net.*;public class DatagramsServerString {  public static void main(String[] args) throws IOException {    //應(yīng)用5556端口創(chuàng)建DatagramSocket類    DatagramSocket datagramSocket = new DatagramSocket(5556);    try {      byte[] buf = new byte[20];      //使用byte數(shù)組創(chuàng)建數(shù)據(jù)包      DatagramPacket packet = new DatagramPacket(buf, buf.length);      System.out.println("等待接收數(shù)據(jù).");      //使用DatagramSocket接口接收客戶端的數(shù)據(jù)包,進(jìn)入等待狀態(tài)      datagramSocket.receive(packet);      String string = "1";      //將字符串轉(zhuǎn)為Bytes()數(shù)組      buf = string.getBytes();      //根據(jù)接收的數(shù)據(jù)包獲取網(wǎng)絡(luò)地址與端口      InetAddress address = packet.getAddress();      int port = packet.getPort();      //重新創(chuàng)建帶有網(wǎng)絡(luò)地址與端口的數(shù)據(jù)包      packet = new DatagramPacket(buf, buf.length, address, port);      //根據(jù)數(shù)據(jù)包的地址與端口發(fā)送數(shù)據(jù)包      datagramSocket.send(packet);      System.out.println("完成數(shù)據(jù)發(fā)送.");    }    catch (IOException e) {      e.printStackTrace();    }  }}