Java客户端/服务器tcp消息不正确

Question

我正在编写一个客户端/服务器应用程序，其中客户端向服务器发送用户名，服务器响应挑战，但我遇到了接收质询的客户端问题。似乎挑战只是被删除或替换为另一个字节数组（每次都恰好相同）。对此的任何建议将不胜感激。

客户代码：

public class ClientOrig {
  public static void main( String[] args ) {
    // Complain if we don't get the right number of arguments. 
    if ( args.length != 1 ) {
      System.out.println( "Usage: Client <host>" );
      System.exit( -1 );
    }

    try {
      // Try to create a socket connection to the server.
      Socket sock = new Socket( args[ 0 ], ServerOriginal.PORT_NUMBER );

      // Get formatted input/output streams for talking with the server.
      DataInputStream input = new DataInputStream( sock.getInputStream() );
      DataOutputStream output = new DataOutputStream( sock.getOutputStream() );

      // Get a username from the user and send it to the server.
      Scanner scanner = new Scanner( System.in );
      System.out.print( "Username: " );
            String name = scanner.nextLine();
      output.writeUTF( name );
      output.flush();

      byte[] challenge = ServerOriginal.getMessage( input );
      System.out.println(challenge);
      String request = "";
      System.out.print( "cmd> " );

      // We are done communicating with the server.
      sock.close();
    } catch( IOException e ){
      System.err.println( "IO Error: " + e );
    }
  }
}

服务器代码：

  public static byte[] getMessage( DataInputStream input ) throws IOException {
    int len = input.readInt();
    byte[] msg = new byte [ len ];
    input.readFully( msg );
    System.out.println("Read: " + msg + " which is " + msg.length);
    System.out.println("Byte to string: " + new String(msg));
    return msg;
  }

  /** Function analogous to the previous one, for sending messages. */
  public static void putMessage( DataOutputStream output, byte[] msg ) throws IOException {
    output.writeInt(msg.length);
    output.write( msg, 0, msg.length );
    System.out.println("Writing: "+ msg + " which is " + msg.length);
    output.flush();

  }

  /** Function to handle interaction with a client.  Really, this should
      be run in a thread. */
  public void handleClient( Socket sock ) {
    try {
      // Get formatted input/output streams for this thread.  These can read and write
      // strings, arrays of bytes, ints, lots of things.
      DataOutputStream output = new DataOutputStream( sock.getOutputStream() );
      DataInputStream input = new DataInputStream( sock.getInputStream() );

      // Get the username.
      String username = input.readUTF();
      System.out.println(username);
      // Make a random sequence of bytes to use as a challenge string.
      Random rand = new Random();
      byte[] challenge = new byte [ 16 ];
      System.out.println(challenge);
      rand.nextBytes( challenge );
      System.out.println(challenge);
      putMessage(output, challenge);
        // Send the client the challenge.
      putMessage( output, challenge );
      getMessage(input);

    } catch ( IOException e ) {
      System.out.println( "IO Error: " + e );
    } finally {
      try {
        // Close the socket on the way out.
        sock.close();
      } catch ( Exception e ) {
      }
    }
  }