socket套接字connect的超时处理

totopper

看unix网络编程，大概知道可以通过SIGALARM信号中断connect，实现超时控制，但实际测试时怎么没效果哇，代码如下：
#include "unp.h"
static void connect_alarm( int );
int connect_timeo( int sockfd, const SA* saptr, socklen_t salen, int nsec )
{
        Sigfunc* sigfunc;
        int n;
        sigfunc = signal ( SIGALRM, connect_alarm );
        if ( alarm(nsec) != 0 )
                sock_msg("connnect_timeo: alarm was already set");
        sock_msg("connecting....");
        if (( n = connect( sockfd, saptr, salen))< 0 )
                {
                        close ( sockfd );
                        if (errno == EINTR )
                                errno = ETIMEDOUT;
                }
        sock_msg("connecting finished!");
        alarm ( 0 );
        signal ( SIGALRM, sigfunc );
        return ( n );
}
static void connect_alarm(int signo )
{
        return;
}
int main(int argc, char** argv)
{
        int sockfd = socket (AF_INET ,SOCK_STREAM,0);
        const char*serverAddr = "192.168.0.101";
        sockaddr_in servaddr;
        servaddr.sin_port = htons ( 80 );
        servaddr.sin_family = AF_INET;
        servaddr.sin_addr.s_addr = inet_addr ( serverAddr );
               
        int ret = connect_timeo( sockfd, (SA*)&servaddr, sizeof (sockaddr_in ),5 );
        if ( ret < 0 )
                sock_err("connect error",0);

       
}