自己写了一个telnet命令

大家都知道，linux中有telnet命令，用于探测tcp连接，功能强大。

最近，我写了一个这个命令，试了一下，靠谱：

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <malloc.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <stdarg.h>
#include <fcntl.h>
#include <time.h>
 
 
int telnetCheckTcp(const char *ip, int port, int tSecond)
{
	int sockClient = socket(AF_INET, SOCK_STREAM, 0);
	int iFinal = 0;
 
	struct sockaddr_in addrSrv;
	addrSrv.sin_addr.s_addr = inet_addr(ip);
	addrSrv.sin_family = AF_INET;
	addrSrv.sin_port = htons(port);
 
	fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0)|O_NONBLOCK);  
	
	int iRet = connect(sockClient, ( const struct sockaddr *)&addrSrv, sizeof(struct sockaddr_in));  // 返回-1不一定是异常
	if (iRet != 0)	
	{  
		if(errno != EINPROGRESS)
		{
			iFinal = -1;	
		}
		else  
		{
			struct timeval tm = {tSecond, 0}; 
			fd_set wset, rset;	
			FD_ZERO(&wset); 
			FD_ZERO(&rset); 
			FD_SET(sockClient, &wset);	
			FD_SET(sockClient, &rset); 
			int time1 = time(NULL);
			int n = select(sockClient + 1, &rset, &wset, NULL, &tm);  
			int time2 = time(NULL);
 
			if(n < 0)	
			{  
			    iFinal = -2;	  
			}  
			else if(n == 0)  
			{  
			    iFinal = -3;	  
			}  
			else if (n == 1)  
			{
			   if(FD_ISSET(sockClient, &wset))	
			   {  
				   iFinal = 0;	 
				   fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0) & ~O_NONBLOCK);  
			   }  
			   else  
			   {  
				   iFinal = -4;	
			   }  
			}
			else
			{
				iFinal = -5;	
			}
		}  
	}  
 
	close(sockClient);
	return iFinal;
}
 
 
int main(int argc, char *argv[])
{
	if(argc != 4)
	{
		printf("error\n");
		return -1;
	}
 
	int iFinal = telnetCheckTcp(argv[1], atoi(argv[2]), atoi(argv[3]));
	printf("iFinal is %d\n", iFinal);
 
	return 0;
}

经调试，OK.