Java与c++之socket通信并c++串口输出

很奇怪Java怎么都遍历不到输出方向的串口，如下图所示

然后

用Java就无法成功发出数据，想了半天没想到解决方法，索性就用c++传，c++很给力，能成功连接串口，于是就用c++作为服务端，Java作为客户端，这里只需要自己编写自己对应部分的代码就ok，

麻烦的是Java向c++传指令时要注意在数据后面加一个，因为c中数据是以这个结尾的，另外char型数组要用num【number】形式来比较。

c++代码如下

#include <WINSOCK2.H>   
#include <stdio.h>    
#include<iostream>
#include<windows.h>
                    
#define PORT           5150    
#define MSGSIZE        1024    
                   
#pragma comment(lib, "ws2_32.lib")   
using namespace std;   
                   
int main()      
{           
    HANDLE hcom;
    hcom = CreateFile("COM2",GENERIC_READ | GENERIC_WRITE,0,NULL,OPEN_EXISTING 
                       ,FILE_ATTRIBUTE_NORMAL,NULL);
    SetupComm(hcom,4096,4096);
    DCB dcb;
    GetCommState(hcom,&dcb);
    dcb.BaudRate = 9600;
    dcb.ByteSize = 8;
    dcb.Parity = 0;
    dcb.StopBits = 1;
    SetCommState(hcom,&dcb);
    char stop[]="$0,0,0#";
    char forward[]="$1,0,0#";
    char backoff[]="$2,0,0#";
    char left_turn[]="$3,0,0#";
    char right_turn[]="$4,0,0#";
    DWORD dwWrittenLen = 0;
    //int k=0;
    WSADATA wsaData;      
    SOCKET sListen;      
    SOCKET sClient;      
    SOCKADDR_IN local;      
    SOCKADDR_IN client;      
    char szMessage[MSGSIZE];
    //char szMessage;
    int a;
    int ret;      
    int iaddrSize = sizeof(SOCKADDR_IN);      
    WSAStartup(0x0202, &wsaData);      
                   
    sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);      
                   
    local.sin_family = AF_INET;      
    local.sin_port = htons(5150);      
    local.sin_addr.s_addr = htonl(INADDR_ANY);      
    bind(sListen, (struct sockaddr *) &local, sizeof(SOCKADDR_IN));      
                   
    listen(sListen, 1);      
                   
    sClient = accept(sListen, (struct sockaddr *) &client, &iaddrSize);      
    printf("Accepted client:%s:%d
", inet_ntoa(client.sin_addr),    
            ntohs(client.sin_port));      
                   
    while (TRUE) {   
    if(ret = recv(sClient, szMessage, MSGSIZE, 0))
    {
        ret = recv(sClient, szMessage, MSGSIZE, 0);    
                    szMessage[ret] = '';  
            
    /*
    if(!WriteFile(hcom,data,8,&dwWrittenLen,NULL))
    {
           fprintf(stderr, "发送数据失败！
");
    }
    k++; 
    */ 
                    if (szMessage[0]==1){
                        a=2;
                    }
                    else if(szMessage[0]==2){
                        a=3;
                    }
                    else if(szMessage[0]==3){
                        a=1;
                    }
                    else if(szMessage[0]==4){
                        a=4;
                    }
                    else if(szMessage[0]==5){
                        a=5;
                    }
                    
                    
                        switch(a){
                        case 1:    
                            WriteFile(hcom,left_turn,8,&dwWrittenLen,NULL);
                            printf("Received [%d bytes]: '%s'
", ret, szMessage); 
                            break;
                        case 2:
                            WriteFile(hcom,forward,8,&dwWrittenLen,NULL);
                            printf("Received [%d bytes]: '%s'
", ret, szMessage); 
                            break;
                        case 3:
                            WriteFile(hcom,backoff,8,&dwWrittenLen,NULL);
                            printf("Received [%d bytes]: '%s'
", ret, szMessage); 
                            break;
                        case 4:
                            WriteFile(hcom,right_turn,8,&dwWrittenLen,NULL);
                            printf("Received [%d bytes]: '%s'
", ret, szMessage);     
                            break;
                        case 5:
                            WriteFile(hcom,stop,8,&dwWrittenLen,NULL);
                            printf("Received [%d bytes]: '%s'
", ret, szMessage);     
                            break;
                        }
                
/*    if(ret==0x00){
    
    }
     if(ret==1){
        
    }    
     if(ret==11){
        WriteFile(hcom,backoff,8,&dwWrittenLen,NULL);
        printf("Received [%d bytes]: '%s'
", ret, szMessage); 
    }
     if(ret==3){
        WriteFile(hcom,left_turn,8,&dwWrittenLen,NULL);
        printf("Received [%d bytes]: '%s'
", ret, szMessage); 
    }
     if(ret==4){
        WriteFile(hcom,right_turn,8,&dwWrittenLen,NULL);
        printf("Received [%d bytes]: '%s'
", ret, szMessage); 
    }
    */
    /*     
    printf("往串口发送数据成功！第%d次
" ,k);
    Sleep(1*1000);  //10s发送一次
    printf("Received [%d bytes]: '%s'
", ret, szMessage);    
    */
                                    
    }
    }
         return 0;      
  }  

Java如下 其中监听key 创建一个面板是必要的，只有这样才能一直监听。

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.Socket;

/**
 * @Author:Tianye Long
 * @Description:
 * @Date:2020/1/2 10:38
 * @Version:1.8
 */
public class ARCar extends JFrame  {
    Socket socket=new Socket("127.0.0.1",5150);
    public static PrintWriter printWriter;
    MyPanel myPanel=null;
    public static void main(String[] args) throws IOException {
        ARCar arCar=new ARCar();
    }
    public ARCar() throws IOException {
        printWriter=new PrintWriter(socket.getOutputStream(), true);
        myPanel=new MyPanel();
        this.add(myPanel);
        this.addKeyListener(myPanel);
        this.setSize(400,200);
        this.setLocation(100,100);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }


}
class MyPanel extends JPanel implements KeyListener{
    char a=1;
    char b=2;
    char c=3;
    char d=4;
    char f=5;
    @Override
    public void paint(Graphics g) {
        super.paint(g);
    }
    @Override
    public void keyTyped(KeyEvent e) {

    }
    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_W) {
            for (int i = 0; i <2 ; i++) {
                ARCar.printWriter.println(a);
            }

        } else if (e.getKeyCode() == KeyEvent.VK_S) {
            for (int i = 0; i < 2; i++) {
                ARCar.printWriter.println(b+"");
            }

        } else if (e.getKeyCode() == KeyEvent.VK_A) {
            for (int i = 0; i < 2; i++) {
                ARCar.printWriter.println(c+"");
            }

        } else if (e.getKeyCode() == KeyEvent.VK_D) {
            for (int i = 0; i < 2; i++) {
                ARCar.printWriter.println(d+"");
            }

        }else if (e.getKeyCode() == KeyEvent.VK_F) {
            for (int i = 0; i < 2; i++) {
                ARCar.printWriter.println(f+"");
            }

        }
    }

    @Override
    public void keyReleased(KeyEvent e) {

    }
}