wifi智慧小車專案，伺服器端主要是基於路由板上跑一個openwrt作業系統。openwrt配置ser2net、mjpg-stream兩個軟體，同時配置json、sqlite3;

ser2net-----通過wifi接受上位機發送的指令，將資料原封不動的網口轉串列埠，發給下位機處理；

mjpg-stream-----通過usb輸入的視訊資料流進行編碼，通過wifi通道給上位機解碼，輸出視屏；

json-----解析上位機發送的json包資訊；

sqlite3----將解析的上位機發送的密碼和賬號插入資料庫，每次遍歷資料庫看是否存在賬號，不存在則註冊；

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這裡就簡單的把程式碼拿出來吧，openwrt的系統裁剪和移植還有交叉編譯工具鏈在沒有文件下，花了很多時間，由於細節太多，有需要的可以私聊；

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <json/json.h>
#include <sqlite3.h>
#include <string.h>
/****************************************************************/
#define REGISER   0
#define LOGIN     1

int buf0[]={0};
int buf1[]={1};

void handler_message(int signum)
{
    waitpid(-1,NULL,WNOHANG);//非阻塞
    return;
}


void do_register(int sockfd,sqlite3 *pdb,char *_username,char *_password,char *filename)
{
        int ret=0;
        char sql[1024]={0};
        int nrow=0,ncolumn=0;
        char *errmsg;
        char **dbresult;

        sprintf(sql,"select *from userinfo where userName='%s';",_username);

        ret=sqlite3_open(filename,&pdb);
        if(ret!=SQLITE_OK)
        {
            fprintf(stderr,"fail to sqlite3_open:%s\n",sqlite3_errmsg(pdb));
            return ;
        }
        

        if(sqlite3_get_table(pdb,sql,&dbresult,&nrow,&ncolumn,&errmsg)!=0)
        {
            fprintf(stderr,"sqlite3 get table error:%s\n",errmsg);
            return ;
        }


        /***********查詢若使用者不存在*****************/
        if(nrow==0)/*******註冊**********/
        {

            bzero(sql,sizeof(sql));
            sprintf(sql,"insert into userinfo values('%s','%s');",_username,_password);
            sqlite3_exec(pdb,sql,NULL,NULL,&errmsg);
          //  printf("ok.....\n");


            if(send(sockfd,buf1,sizeof(buf1),0)<0)
            {
                perror("fail to send");
                return ;
            }

        }
        /************查詢若使用者名稱存在***************/
        else
        {
            if(send(sockfd,buf1,sizeof(buf1),0)<0)
            {
                perror("fail to send");
                return ;
            }
        }

       sqlite3_free_table(dbresult);
}

void do_login(int sockfd,sqlite3 *pdb,char *_username,char *_password,char *filename)
{

    int ret=0;
    char sql[1024]={0};
    int nrow=0,ncolumn=0;
    char *errmsg;
    char **dbresult;


    sprintf(sql,"select *from userinfo where userName='%s';",_username);

    ret=sqlite3_open(filename,&pdb);
    if(ret!=SQLITE_OK)
    {
        fprintf(stderr,"fail to sqlite3_open:%s\n",sqlite3_errmsg(pdb));
        return ;
    }
        
    /************查詢查資料表****************/          
    if(sqlite3_get_table(pdb,sql,&dbresult,&nrow,&ncolumn,&errmsg)!=0)
    {
        fprintf(stderr,"sqlite3 get table error:%s\n",errmsg);
        return ;
    }


    /***********使用者不存在*****************/
    if(nrow==0)
    {
        if(send(sockfd,buf0,sizeof(buf0),0)<0)
        {
            perror("fail to send");
            return ;
        }
    }
    /************使用者名稱存在***************/
    else
    {
        if(send(sockfd,buf1,sizeof(buf1),0)<0)
        {
            perror("fail to send");
            return ;
        }
    }
    sqlite3_free_table(dbresult);
    return;

}



void do_client(int sockfd)
{
    int n = 0;
    unsigned char buf[1024]={0};
    json_object *obj;//定義json物件 
    char _username[25];
    char _password[25];     
    int ret=0;
    char sql[1024]={0};
    char *errmsg;
    char **dbresult;
    sqlite3 *pdb=NULL;
    char* filename = "/home/ubuntu/project/carinfo.db";
    

    while(1)
    {
        bzero(buf,sizeof(buf));
        n = recv(sockfd,buf,sizeof(buf),0);
        if(n <= 0)
        {
            perror("fail to recv");
            exit(EXIT_FAILURE);
        }        
/***json解析***/
        printf("recv_buf= %s\n",buf);//接受對方發來的JSON物件
        printf("buf[0]=%d\n",buf[0]);


        obj=json_tokener_parse(buf+1);//解析json物件
        json_object *new_object=json_object_object_get(obj,"userName");//根據鍵名獲取小物件
        printf("%s\n",json_object_get_string(new_object));//獲取json物件裡的字串
        strcpy(_username,json_object_get_string(new_object));

        new_object=json_object_object_get(obj,"passWord");//根據鍵名獲取小物件
        printf("%s\n",json_object_get_string(new_object));//獲取json物件裡的字串
        strcpy(_password,json_object_get_string(new_object));

/***SQL*******/
        sprintf(sql,"select *from userinfo where userName='%s';",_username);

        ret=sqlite3_open(filename,&pdb);
        if(ret!=SQLITE_OK)
        {
            fprintf(stderr,"fail to sqlite3_open:%s\n",sqlite3_errmsg(pdb));
            return ;
        }
/***登入******/
        if(buf[0]=='1')
        {
              do_login(sockfd,pdb,_username,_password,filename);
        }
/***註冊*****/
        else if(buf[0]=='2')
        {
            do_register(sockfd,pdb,_username,_password,filename);
        }
        exit(EXIT_SUCCESS);
}


//./a.out ip port
int main(int argc, const char *argv[])
{
    int listen_fd;
    int connect_fd;
    struct sockaddr_in ser_addr;
    struct sockaddr_in client_addr;
    socklen_t len = sizeof(struct sockaddr);
    int n = 0;
    char buf[1024] = {0};
    pid_t pid;


    if(argc != 3)
    {
        fprintf(stderr,"Uage: %s ip port ",argv[0]);
        exit(EXIT_FAILURE);
    }
    
    if(signal(SIGCHLD,handler_message) == SIG_ERR)
    {
        perror("fail to signal");
        exit(EXIT_FAILURE);
    }
    //1.建立一個監聽套接字
    listen_fd = socket(AF_INET,SOCK_STREAM,0);
    if(listen_fd < 0)
    {
        perror("fail to socket");
        exit(EXIT_FAILURE);
    }

    //2.伺服器地址賦值
    bzero(&ser_addr,len);
    ser_addr.sin_family = AF_INET;
    ser_addr.sin_port = htons(atoi(argv[2]));
    ser_addr.sin_addr.s_addr = inet_addr(argv[1]);

    //3.繫結套接字
    if(bind(listen_fd,(struct sockaddr *)&ser_addr,len) < 0)
    {
        perror("fail to bind");
        exit(EXIT_FAILURE);
    }

    //4.開啟監聽，設定監聽佇列的長度10
    listen(listen_fd,10);
    printf("listen ......I\n");
    while(1)
    {

        connect_fd = accept(listen_fd,(struct sockaddr *)&client_addr,&len);
        if(connect_fd < 0)
        {
            perror("fail to accept");
            exit(EXIT_FAILURE);
        }

        printf("----------------------------------------------------");
        printf("connect_fd = %d\n",connect_fd);
        printf("client_addr.sin_port = %d\n",ntohs(client_addr.sin_port));
        printf("client_addr.sin_addr = %s\n",inet_ntoa(client_addr.sin_addr));

        //
        pid = fork();

        if(pid < 0)
        {
            perror("fail to fork");
            exit(EXIT_FAILURE);
        }else if(pid == 0)    //子程序負責資料的接收
        {
            do_client(connect_fd);
            close(listen_fd);

        }else{
            close(connect_fd);
        }

    }
    
    return 0;
  }
}