用Java清除数据报缓冲区

Question

所以我从互联网上获得了这个简单的udp客户端/服务器代码,它的工作原理.但是,当我输入比我之前输入的东西更短的东西时,我会剩下剩下的字符.例如,如果我先输入:

kitty

然后输入:

cat

第二个印刷品如下:

catty

我一直在寻找其他有类似问题的人,其中大部分似乎都是通过清除字节数组来解决的.但是,如果我尝试实现他们的答案,它不能解决我的问题.我需要做什么,并且(可能更重要的是)代码应该去哪里？这是代码:

客户:

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

class UDPClient
 {
    public static void main(String args[]) throws Exception
    {
       BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
       DatagramSocket clientSocket = new DatagramSocket();
       InetAddress IPAddress = InetAddress.getByName("localhost");
       byte[] sendData = new byte[1024];
       byte[] receiveData = new byte[1024];
       String sentence = inFromUser.readLine();
       sendData = sentence.getBytes();
       DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 20700);
       clientSocket.send(sendPacket);
       DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
       clientSocket.receive(receivePacket);
       String modifiedSentence = new String(receivePacket.getData());
       System.out.println("FROM SERVER:" + modifiedSentence);
       clientSocket.close();
    }
 }

服务器:

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

class UDPServer
 {
    public static void main(String args[]) throws Exception
       {
          DatagramSocket serverSocket = new DatagramSocket(21200);
          byte[] receiveData = new byte[1024];
          byte[] sendData = new byte[1024];
          while(true)
                {
                   DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
                   serverSocket.receive(receivePacket);
                   String sentence = new String( receivePacket.getData(), 0, receivePacket.getLength());
                   System.out.println("RECEIVED: " + sentence);
                   InetAddress IPAddress = receivePacket.getAddress();
                   int port = receivePacket.getPort();
                   String capitalizedSentence = sentence.toUpperCase();
                   sendData = capitalizedSentence.getBytes();
                   DatagramPacket sendPacket =  new DatagramPacket(sendData, sendData.length, IPAddress, port);
                   serverSocket.send(sendPacket);
                }
       }
 }

Answer 1

您不需要清除字节数组,但是您需要通过getLength()方法在接收之后注意DatagramPacket的长度; 例如:

new String(packet.getData(), packet.getOffset(), packet.getLength());

您在服务器中正确地执行了此操作,但在客户端中却没有.

您还需要在呼叫前重置长度receive().否则,DatagramPacket将继续缩小到目前为止收到的最小数据包的长度.