socket連接超時判斷

select 方式

判斷m_server的m_port端口是否可以連上，超時限制爲nTimeOut秒

BOOL ConnectTest(char * m_server,int m_port) 
{ 

        struct hostent* host = NULL; 
        struct sockaddr_in saddr; 
        unsigned int s = 0; 
        BOOL  ret; 
        time_t start; 
        int error; 
        host = gethostbyname (m_server); 
        if (host==NULL)return  FALSE; 

        saddr.sin_family = AF_INET; 
        saddr.sin_port = htons(m_port); 
        saddr.sin_addr = *((struct in_addr*)host->h_addr); 


        if( (s=socket(AF_INET, SOCK_STREAM, 0))<0){ 
                return FALSE; 
        } 


        fcntl(s,F_SETFL, O_NONBLOCK); 

        if(connect(s,(struct sockaddr*)&saddr, sizeof(saddr)) == -1) { 
                if (errno == EINPROGRESS){// it is in the connect process 
                        struct timeval tv; 
                        fd_set writefds; 
                        tv.tv_sec = m_nTimeOut; 
                        tv.tv_usec = 0; 
                        FD_ZERO(&writefds); 
                        FD_SET(s, &writefds); 
                        if(select(s+1,NULL,&writefds,NULL,&tv)>0){ 
                                int len=sizeof(int); 
                               //下面的一句一定要，主要針對防火牆 
                                getsockopt(s, SOL_SOCKET, SO_ERROR, &error, &len); 
                                if(error==0) ret=TRUE; 
                                else ret=FALSE; 
                        }else   ret=FALSE;//timeout or error happen 
                }else ret=FALSE; 
        } 
        else    ret=TRUE; 

        close(s); 
        return ret; 
}