解决方案思想：    通过把socket设置为非阻塞模式，然后通过select函数自己设置定时，检测套接字描述符是否可用。

windows端实现上代码： 过于粗略，仅呈思想

#include <winsock2.h>
#include <Windows.h>
#include <conio.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 main(int argc, char *argv[]) 
{
    printf("==main===\n");fflush(stdout);
    //Winsows下启用socket
    WSADATA wsadata;
    if (WSAStartup(MAKEWORD(1, 1), &wsadata) == SOCKET_ERROR) {
        printf("WSAStartup() fail\n");fflush(stdout);
        exit(0);
    }
    printf("==WSAStartup ok ===\n");fflush(stdout);
      int sockClient = socket(AF_INET, SOCK_STREAM, 0);
      struct sockaddr_in addrSrv;
      addrSrv.sin_addr.s_addr = inet_addr(argv[1]);
      addrSrv.sin_family = AF_INET;
      addrSrv.sin_port = htons(atoi(argv[2]));
 //fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0)|O_NONBLOCK); 
    printf("==goto  ioctlsocket ok ===\n");fflush(stdout);
    unsigned long ul=1;
     int ret=ioctlsocket(sockClient,FIONBIO,(unsigned long *)&ul);    //设置成非阻塞模式
    if(ret==SOCKET_ERROR)   //设置失败
    {
        printf("socket ioctl error%d\n", WSAGetLastError());fflush(stdout);
        return -10;
    }
    printf("==set sucess to connect===\n");fflush(stdout);
  int iRet = connect(sockClient, ( const struct sockaddr *)&addrSrv, sizeof(struct sockaddr_in));
 printf("connect iRet is %d, errmsg:%s\n", iRet, strerror(errno));
 fflush(stdout); // 返回-1不一定是异常
 if (iRet != 0) 
 {
/*     
   if(errno != EINPROGRESS)
 {
  printf("connect error:%s\n", strerror(errno)); fflush(stdout);
 }
 else
     */
 {
  printf("socket ===========\n");
  struct timeval tm = {5, 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);
  printf("time gap is %d\n", time2 - time1);fflush(stdout);
  if(n < 0) 
  { 
   printf("select error, n is %d\n", n); fflush(stdout);
  } 
  else if(n == 0) 
  { 
   printf("connect time out\n"); fflush(stdout);
  } 
  else if (n == 1) 
  {
   if(FD_ISSET(sockClient, &wset)) 
   { 
    printf("connect ok!\n"); fflush(stdout);
    //fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0) & ~O_NONBLOCK); 
   } 
   else
   { 
    printf("unknow error:%s\n", strerror(errno)); fflush(stdout);
   } 
  }
  else
  {
  printf("oh, not care now, n is %d\n", n);fflush(stdout);
  }
 } 
 } 
  printf("I am here!\n");fflush(stdout);
  //ioctlsocket(sockClient, FIONBIO, &ul); //设置为阻塞模式 阻塞时间为timeout时间
  getchar();
  closesocket(sockClient);
   
    WSACleanup();
    return 0;

}

linux端实现：

#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 main(int argc, char *argv[]) 
{
  int sockClient = socket(AF_INET, SOCK_STREAM, 0);
  struct sockaddr_in addrSrv;
  addrSrv.sin_addr.s_addr = inet_addr(argv[1]);
  addrSrv.sin_family = AF_INET;
  addrSrv.sin_port = htons(atoi(argv[2]));
  fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0)|O_NONBLOCK); 
  int iRet = connect(sockClient, ( const struct sockaddr *)&addrSrv, sizeof(struct sockaddr_in));
  printf("connect iRet is %d, errmsg:%s\n", iRet, strerror(errno)); // 返回-1不一定是异常

 if (iRet != 0) 
 { 
   if(errno != EINPROGRESS)
   {
        printf("connect error:%s\n", strerror(errno)); 
   }
   else
   {
          struct timeval tm = {5, 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);
      printf("time gap is %d\n", time2 - time1);
      if(n < 0) 
      { 
           printf("select error, n is %d\n", n); 
      } 
      else if(n == 0) 
      { 
           printf("connect time out\n"); 
      } 
      else if (n == 1) 
        {
         if(FD_ISSET(sockClient, &wset)) 
            { 
            printf("connect ok!\n"); 
            fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0) & ~O_NONBLOCK); 
         } 
         else
         { 
            printf("unknow error:%s\n", strerror(errno)); 
          } 
      }
       else
         {
           printf("oh, not care now, n is %d\n", n);
      }
    } 
  } 
  printf("I am here!\n");
  getchar();
  close(sockClient);
  return 0;
}
 

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