Question

我正在使用UDP编写客户端 - 服务器聊天程序。如果客户端或服务器发送消息，并且它们发送的下一条消息比它们发送的上一条消息短，则较长消息的一部分将放在较短消息的末尾。这是我第一次使用UDP而且我不知道是什么导致这种情况，我使用TCP制作了一个类似的程序并且没有这个问题。

客户看到的内容：

客户：你好，你好吗？

服务器：我很好，谢谢，你呢？

客户：很好

服务器看到了什么：

客户：你好，你好吗？

服务器：我很好，谢谢，你呢？

客户：太好了，你好吗？

我的服务器代码：

public class ChatServer implements Runnable
{  
        public static void main(String[] args) throws Exception
        {
            new Thread(new ChatServer()).start();
        }

        @Override
        public void run()
        {
            try 
            {
                    BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));    

                    DatagramSocket serverSocket = new DatagramSocket(9876);

                    byte[] receiveData = new byte[65508];
                    byte[] sendData = new byte[65508];

                    System.out.println("Enter a username: ");
                    String serverUsername = inFromUser.readLine();

                    System.out.println("Send message...");

                    while(true)
                    { 
                            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);                   
                            serverSocket.receive(receivePacket);       

                            String clientSentence = new String(receivePacket.getData());
                            System.out.println(clientSentence);

                            InetAddress IPAddress = receivePacket.getAddress();

                            int port = receivePacket.getPort(); 

                            System.out.print("Me: ");
                            String serverSentence = serverUsername + ": " + inFromUser.readLine();

                            sendData = serverSentence.getBytes(); 

                            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);                   
                            serverSocket.send(sendPacket); 
                    }
              } 

              catch (IOException ex) 
              {
                      Logger.getLogger(ChatServer.class.getName()).log(Level.SEVERE, null, ex);
              }
       }
}

我的客户代码：

public class ChatClient 
{
        public static void main(String[] args) throws Exception
        {
                BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));       
                try (DatagramSocket clientSocket = new DatagramSocket()) 
                {
                        InetAddress IPAddress = InetAddress.getByName("localhost");       
                        byte[] sendData = new byte[65508];       
                        byte[] receiveData = new byte[65508];

                        System.out.println("Enter a username: ");
                        String clientUsername = inFromUser.readLine();

                        System.out.println("Send message...");

                        while(true)
                        {      
                                System.out.print("Me: ");
                                String clientSentence = clientUsername + ": " + inFromUser.readLine();
                                sendData = clientSentence.getBytes();
                                DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);       
                                clientSocket.send(sendPacket);                                                         

                                DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);       
                                clientSocket.receive(receivePacket);       
                                String serverSentence = new String(receivePacket.getData()); 
                                System.out.println(serverSentence);
                        }
                }

                catch(Exception e)
                {
                        e.getMessage();
                }
        }
}

Answer 1

接收数据包最初为空终止。它充满了网络数据。在每次构造clientSentence之后，您需要告诉字符串要读取多少字节或将receiveData清零。使用数据包的长度是解决此问题的正确方法。

变化：

   String clientSentence = new String(receivePacket.getData());

要：

  String clientSentence = new String(receivePacket.getData() ,0 , receivePacket.getLength());

Java UDP聊天程序：第一个消息的一部分被附加到第二个消息

1 个答案: