Linux下Socket连接超时的一种实现方法

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <time.h>

int main(int argc, char *argv[])
{
int fd, retval;
struct sockaddr_in addr;
struct timeval timeo = {3, 0};
socklen_t len = sizeof(timeo);
fd_set set;

fd = socket(AF_INET, SOCK_STREAM, 0);
if (argc == 4)
timeo.tv_sec = atoi(argv[3]);
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(argv[1]);
addr.sin_port = htons(atoi(argv[2]));
printf("%d/n", time(NULL));
if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == 0) {
printf("connected/n");
return 0;
}
if (errno != EINPROGRESS) {
perror("connect");
return -1;
}
FD_ZERO(&set);
FD_SET(fd, &set);
retval = select(fd + 1, NULL, &set, NULL, &timeo);
if (retval == -1) {
perror("select");
return -1;
} else if(retval == 0) {
fprintf(stderr, "timeout/n");
printf("%d/n", time(NULL));
return 0;
}
printf("connected/n");

return 0;
}