自己实现telnet程序

转自：http://blog.csdn.net/gujintong1110/article/details/44278535

#include <stdio.h>  
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>  
#include <sys/socket.h>  
#include <netinet/in.h>  
#include <arpa/inet.h>  
#include <sys/types.h>
#include <sys/wait.h>
#include <pthread.h>

int save_fd;
#define BUFSIZE 1024
/*telnet_cmd:ff fb 01 ff fb 03 ff fc 1f*/
const unsigned char cmd_telnet[9] = {0xff, 0xfb, 0x01, 0xff, 0xfb, 0x03, 0xff, 0xfc, 0x1f};
char cmdLine[1024] = {0};

void task_process(int sockfd);
int telnetd(void);
void *telnetd_pthread(void * arg);
void *task_process_pthread(void *arg) ;

/*启动telnet服务*/
int telnetd_start()
{
#if 1
    pthread_t id;
    int i,ret;

    ret=pthread_create(&id,NULL,(void *) telnetd_pthread,NULL);
    if(ret!=0){
        printf ("Telnet: telnet_starting.......err!\n");
        return -1;
    }

#else 
    int pid;
    int status;

    if(pid=fork()) {
        //exit(0);        //是父进程，结束父进程
        waitpid(-1, &status, WNOHANG | WUNTRACED | WCONTINUED);
        return 0;
    } else if(pid < 0) {
        return -1;//exit(1);        //fork失败，退出
    }
    printf("Telnet: telnet_starting.......\n");
    telnetd();
#endif  
}


/*telnet 主服务任务*/
//int main(int argc, char *argv[])
int telnetd(void)  
{  
    pid_t fpid;
    int status;
    int server_sockfd;//服务器端套接字  
    int client_sockfd;//客户端套接字  
    int len;  
    struct sockaddr_in server_addr;   //服务器网络地址结构体  
    struct sockaddr_in remote_addr; //客户端网络地址结构体  
    int sin_size;  
    memset(&server_addr,0,sizeof(server_addr)); //数据初始化--清零  
    server_addr.sin_family=AF_INET; //设置为IP通信  
    server_addr.sin_addr.s_addr=htonl(INADDR_ANY);//服务器IP地址--允许连接到所有本地地址上  
    server_addr.sin_port=htons(23); //服务器telnet端口号  

    //init_telnetd();

    /*创建服务器端套接字--IPv4协议，面向连接通信，TCP协议*/  
    if((server_sockfd=socket(AF_INET,SOCK_STREAM,0))<0)  
    {    
        perror("socket");  
        return -1;  
    }  

        /*将套接字绑定到服务器的网络地址上*/  
    if (bind(server_sockfd,(struct sockaddr *)&server_addr,sizeof(struct sockaddr))<0)  
    {  
        perror("bind");  
        return -1;  
    }  

    /*监听连接请求*/  
    listen(server_sockfd,1);  

    printf("Telnet: listening for telnet requests....\n");

    sin_size=sizeof(struct sockaddr_in);  
    while(1) {      
        /*等待客户端连接请求到达*/  
        if((client_sockfd=accept(server_sockfd,(struct sockaddr *)&remote_addr,&sin_size))<0)  
        {  
            perror("accept");  
            return 1;  
        }  
        //printf("accept client %s\n",inet_ntoa(remote_addr.sin_addr));  
#if 0       
        fpid = fork();
        if (fpid < 0) {
               perror("call fork() err!\n");
               exit(1);
        } else if (fpid == 0) {
               task_process(client_sockfd);
               close(client_sockfd);
               exit(0);
        } else {
            waitpid(-1, &status, WNOHANG | WUNTRACED | WCONTINUED);
        }
#else 
        pthread_t id;
        int i,ret;

        ret=pthread_create(&id,NULL,(void *) task_process_pthread,(void *)client_sockfd);
        if(ret!=0){
            printf ("Telnet: telnet_starting.......err!\n");
            return -1;
        }
        pthread_join(id,NULL);
#endif      

    }   
    close(client_sockfd);  
    close(server_sockfd);  
    return 0;   
} 
void * telnetd_pthread(void *arg)
{
    telnetd();  
}
/*发送telnet协议命令*/
int send_telnet_cmd(int fd)
{
    return write(fd, cmd_telnet, sizeof(cmd_telnet));
}
/*读取命令字符串*/
int read_cmdline(int sockfd, char *cmdLine, int size)
{
    int ret, rev_count = 0;
    char *buf = NULL;
    buf = cmdLine;
    while(1 == (ret = read(sockfd, buf, 1))) {
        rev_count++;
        if(rev_count > BUFSIZE - 2) {
            return rev_count;
        }
        if(*buf == '\n') {
            return rev_count;
        }
        buf++;
    }
    return ret;
} 
/*输出重定向*/
int ioStdSet(int src_fd, int dest_fd, int *save_fd) 
{
    *save_fd = dup(dest_fd);
    dup2(src_fd, dest_fd);
    //close(src_fd);
    return *save_fd;
}
/*恢复输出重定向*/
void recoverIoStdSet(int src_fd, int dest_fd) 
{
    dup2(src_fd, dest_fd);
    close(src_fd);
}
/*解析字符串*/
int cmd_analyze(char *cmd)
{
    unsigned char *ptr = NULL;
    unsigned char *ptr_tmp;

    if(strlen(cmd) < 12 || strlen(cmd) > 48) {
        return -1;
    }
    /*去除多余的换行符及其他多余字符*/
    while((ptr = strstr(cmd, "\r")) != 0 ) {
        while(*ptr != 0) {
            *ptr = *(ptr+1);
            ptr++;
        }
    }

    while((ptr = strstr(cmd, "\n")) != 0 ) {
        while(*ptr != 0) {
            *ptr = *(ptr+1);
            ptr++;
        }
    }

#if 1
    ptr = cmd;
    while((!((*ptr > 'a' && *ptr < 'z') || (*ptr > 'A' && *ptr < 'Z') || (*ptr > '0' && *ptr < '9'))) && (*ptr != 0)) {
        ptr_tmp = ptr;
        while(*ptr_tmp != 0) {
            *ptr_tmp = *(ptr_tmp+1);
            ptr_tmp++;
        }
    }

#endif  
    if(strlen(cmd) < 12 || strlen(cmd) > 48) {
        return -1;
    }
    return 0;
}
/*执行命令并回显到telnet终端*/
int cmd_process(int fd, char *cmdLine)
{
    ioStdSet(fd, 1, &save_fd); /*标准输出重定向*/

    /*这里添加命令处理函数*/
    /*示例*/
    printf("Welcome to Telnet server.[%s]\n",cmdLine);

    recoverIoStdSet(save_fd, 1); /*恢复输出重定向*/
    return 0;
}
/*telnet交互处理函数*/
void task_process(int sockfd)
{
    char cmdLine[BUFSIZE]={0};
    int count = 0;
    int i=0,tmp = 0;
    int ret;

    while(1) {

        send_telnet_cmd(sockfd);

        ioStdSet(sockfd, 1, &save_fd);
        printf("\r\r\nlinux>");
        recoverIoStdSet(save_fd, 1);

        memset(cmdLine, 0, sizeof(cmdLine));

        count = read_cmdline(sockfd, cmdLine, BUFSIZE);
        if(count <= 0) {
            //perror("read err");
            //exit(1);对方断开连接，返回
            return ;
        }
        ret = cmd_analyze(cmdLine);
        //printf("[%s,%d]rev count:%d,buf:%s\n",__FUNCTION__,__LINE__,count, cmdLine);
        if(ret == 0) {
            cmd_process(sockfd, cmdLine);
        }

    }
}
void *task_process_pthread(void *arg) 
{
    int sockfd;
    sockfd = (int) arg;
    task_process(sockfd);

     pthread_exit((void *)1);
}