java和c使用socket通信时，发送报文的问题

Question

问题详细描述：java是客户端，c语言是服务端。程序的目的是java发送报文过去 ，服务器能够识别。但是c语言写的服务端是很多年前的，目前已经无法对服务端作任何修改，c接收报文是用char定义的，报文是定长报文，不够的用空格补全，格式为包头+报文长度+报文内容(1字节+4字节+300字节)，包头是6，报文长度是0300，报文内容由下图的结构体定义。java使用getBytes()方法，获取了字节数组，发送过去后服务端报错，报错信息为包头错误，后来发现那边接收的是6对应ASCII码，请问这应该如何解决呢？java测试代码如下

package Demo01;

import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class send {
    public static void main(String[] args) {
        try {
            iSend("172.33.xx.xx",10000);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void iSend(String IP,int PORT) throws IOException{
         String baotou = "6";
         String blen= "0300";
         String id = "0001";
         String sysid = "1111";
         String sysname = "disk";
         String type = "11";
         String level = "1";
         String content = "sendcontent";

            Socket socket = null;
            BufferedOutputStream bos = null;
            String message = "" ;

        List <Object> messList = new ArrayList();
        messList.add(baotou);       
        messList.add(blen); 
        messList.add(id);       
        messList.add(sysid);        
        messList.add(sysname);  
        messList.add(type);     
        messList.add(level);        
        messList.add(content);

        List <Object> messList2 = new ArrayList();
        messList2.add(changeString(messList.get(0).toString(),1));
        messList2.add(changeString(messList.get(1).toString(),4));
        messList2.add(changeString(messList.get(2).toString(),4));
        messList2.add(changeString(messList.get(3).toString(),8));
        messList2.add(changeString(messList.get(4).toString(),16));
        messList2.add(changeString(messList.get(5).toString(),16));
        messList2.add(changeString(messList.get(6).toString(),16));
        messList2.add(changeString(messList.get(7).toString(),240));
        for(Iterator<Object> it = messList2.iterator();it.hasNext();){
            message += it.next();
        }
        System.out.println("报文为："+message);
            try {
                 socket = new Socket(IP,PORT);
                 bos = new BufferedOutputStream(socket.getOutputStream());
                  byte [] buf = message.getBytes();
                    bos.write(buf,0,buf.length);
                    bos.flush();
            } catch (UnknownHostException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally{
                if(socket != null){
                    socket.close();
                }

            }
    }
/**
     * 
     *设置定长报文，用空格补齐
     * @param object 报文集合
     * @param len 报文的规定长度
     * @return 
     */
    public static  String  changeString(String list,int len){
        for(int ListLen = list.length();ListLen < len;ListLen++){
            list +=" ";
        }
        return list;
    }
}

Answer 1

https://blog.csdn.net/yutianzuijin/article/details/24807417