定时connect

转载的，原文http://my.oschina.net/u/2408078/blog/481199

//这个方法的原理就是，利用系统信号的异步处理打断connect这种阻塞型的系统调用

#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>
#include <netdb.h> //for gethostnyname
#include <sys/signal.h> //for sigaction(int,...,...)
#include <sys/wait.h>// for wait()
#include <sys/types.h>//for pid_t


typedef void Sigfunc(int);


Sigfunc* signal(int signo,Sigfunc* func)
{
struct sigaction act,oact;

act.sa_handler = func;//signal handler
sigemptyset(&act.sa_mask);//undef signal mask
act.sa_flags = 0;//signal handle method

if(SIGALRM == signo){
#ifdef SA_INTERRUPT
act.sa_flags |= SA_INTERRUPT;/* SunOS 4.x*/
#endif
}else{
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART;/*SVR4, 4.4BSD*/
#endif
}
if(sigaction(signo,&act,&oact) < 0)
return (SIG_ERR);
return oact.sa_handler;
}


void SigHandler(int signo)
{
printf("connect timeout\n");
return;
}


int main(void)
{
int sock;
int ret;
struct sockaddr_in host;

host.sin_family = AF_INET;
host.sin_addr.s_addr = inet_addr("216.58.221.228");
host.sin_port = htons(80);

sock = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(sock < 0)
{
printf("socket failed\n");
return -1;
}

signal(SIGALRM,SigHandler);//注册个信号处理函数
alarm(5);//定时5秒，若connect5秒后还未返回，则会被打断

if(connect(sock,(struct sockaddr*)&host,sizeof(host)) < 0)
{

//失败，或者被打断
alarm(0);
perror("connect failed");
close(sock);
return -1;
}
alarm(0);
close(sock);
printf("connect success\n");
return 0;
}