Socket编程初级问题，关于消息发送

Question

本人刚接触java以及socket编程，入门级水平。
现已知客户端跟服务端java代码如下：

／／服务端
import java.net.*; // for Socket, ServerSocket, and InetAddress
import java.io.*; // for IOException and Input/OutputStream

public class TCP_Server
{

private static final int BUFSIZE = 32; // Size of receive buffer

public static void main(String[] args) throws IOException
{

if (args.length != 1)  // Test for correct # of args
  throw new IllegalArgumentException("Parameter(s): <Port>");

int servPort = Integer.parseInt(args[0]);

// Create a server socket to accept client connection requests
ServerSocket servSock = new ServerSocket(servPort);

int recvMsgSize;   // Size of received message

byte[] byteBuffer = new byte[BUFSIZE];  // Receive buffer

for (;;) { // Run forever, accepting and servicing connections
  Socket clntSock = servSock.accept();     // Get client connection

  System.out.println("Handling client at " +
    clntSock.getInetAddress().getHostAddress() + " on port " +
         clntSock.getPort());

  InputStream in = clntSock.getInputStream();
  OutputStream out = clntSock.getOutputStream();

  // Receive until client closes connection, indicated by -1 return
  while ((recvMsgSize = in.read(byteBuffer)) != -1)

/*
（添加代码，企图改变字符串顺序）

*/

   out.write(byteBuffer, 0, recvMsgSize);




  clntSock.close();  // Close the socket.  We are done with this client!
}
/* NOT REACHED */

}
}

／／客户端
import java.net.*; // for Socket
import java.io.*; // for IOException and Input/OutputStream

public class TCPEchoClient {

public static void main(String[] args) throws IOException {

if ((args.length < 2) || (args.length > 3))  // Test for correct # of args
  throw new IllegalArgumentException("Parameter(s): <Server> <Word> [<Port>]");

String server = args[0];       // Server name or IP address
// Convert input String to bytes using the default character encoding
byte[] byteBuffer = args[1].getBytes();

int servPort = (args.length == 3) ? Integer.parseInt(args[2]) : 7;

// Create socket that is connected to server on specified port
Socket socket = new Socket(server, servPort);
System.out.println("Connected to server...sending echo string");

InputStream in = socket.getInputStream();
OutputStream out = socket.getOutputStream();

out.write(byteBuffer);  // Send the encoded string to the server

// Receive the same string back from the server
int totalBytesRcvd = 0;  // Total bytes received so far
int bytesRcvd;           // Bytes received in last read
while (totalBytesRcvd < byteBuffer.length) {
  if ((bytesRcvd = in.read(byteBuffer, totalBytesRcvd,  
                    byteBuffer.length - totalBytesRcvd)) == -1)
    throw new SocketException("Connection close prematurely");
  totalBytesRcvd += bytesRcvd;
}

System.out.println("Received: " + new String(byteBuffer));

socket.close();  // Close the socket and its streams

}
}

一般情况下，是开两个终端分别运行服务端与客户端，
先执行服务端，显示如下：
g136@ispc29Lx:~$ java TCP_Server 50000

再执行客户端，依次输入IP 字符串 port号，显示如下
g136@ispc29Lx:~$ java TCPEchoClient 150.86.64.169 ab 50000

然后客户端跟服务端都会产生反应，如下：
g136@ispc29Lx:~$ java TCP_Server 50000
Handling client at 150.86.64.169 on port 58002

g136@ispc29Lx:~$ java TCPEchoClient 150.86.64.169 ab 50000
Connected to server...sending echo string
Received: ab

输入的是ab，服务端原封不动的返回的也是ab，我希望能在服务端添加一段代码，使返回的字符顺序改变成ba；或者把ab变成大写，怎么都行，只是希望能对原字符串进行改变。
第一次提问题，还请多多包涵。

Answer 1

直接贴代码吧，修改了服务端的代码，客户端没有修改。主要修改的是服务端增加一个字符串顺序逆序的方法。
你的代码很好了，没有什么问题，很棒的是全部英文，另外粘贴到Eclipse中没有警告和错误，很棒。

package com.test.jvm;

//服务端
import java.net.*; // for Socket, ServerSocket, and InetAddress
import java.io.*; // for IOException and Input/OutputStream

public class TCP_Server {
    private static final int BUFSIZE = 32; // Size of receive buffer

    public static void main(String[] args) throws IOException {
        if (args.length != 1) // Test for correct # of args
            throw new IllegalArgumentException("Parameter(s): <Port>");

        int servPort = Integer.parseInt(args[0]);

        // Create a server socket to accept client connection requests
        ServerSocket servSock = new ServerSocket(servPort);

        int recvMsgSize; // Size of received message

        byte[] byteBuffer = new byte[BUFSIZE]; // Receive buffer

        for (;;) { // Run forever, accepting and servicing connections
            Socket clntSock = servSock.accept(); // Get client connection

            System.out.println("Handling client at "
                    + clntSock.getInetAddress().getHostAddress() + " on port "
                    + clntSock.getPort());

            InputStream in = clntSock.getInputStream();
            OutputStream out = clntSock.getOutputStream();

            // Receive until client closes connection, indicated by -1 return
            while ((recvMsgSize = in.read(byteBuffer)) != -1) {
                /*
                 * （添加代码，企图改变字符串顺序）
                 */
                byte[] changeOrder = changeOrder(byteBuffer, recvMsgSize);
                out.write(changeOrder, 0, recvMsgSize);
            }

            clntSock.close(); // Close the socket. We are done with this client!
        }
        /* NOT REACHED */
    }

    /**
     * change order, for example input <code>abc</code> then output
     * <code>cba</code>
     * 
     * @param byteBuffer
     *            receive bytes
     * @param recvMsgSize
     *            valid length of the receive bytes, cannot larger than
     *            byteBuffer's length.
     * @return
     */
    private static byte[] changeOrder(byte[] byteBuffer, int recvMsgSize) {
        byte[] result = new byte[recvMsgSize];
        for (int i = 0; i < recvMsgSize; i++) {
            result[i] = byteBuffer[recvMsgSize - 1 - i];
        }
        return result;
    }
}