网络超时检测3

设置定时器(timer), 捕捉SIGALRM信号

void  handler(int signo){return;}
      struct sigaction  act;
      sigaction(SIGALRM, NULL, &act);
      act.sa_handler = handler;
      act.sa_flags &= ~SA_RESTART;//清除掉SIGALRM信号的SA_RESTART
      sigaction(SIGALRM, &act, NULL);
      alarm(5);
      if (recv(,,,) < 0) ……