方案1：
int connect_socket_timeout(int sockfd,char *dest_host, int port, int timeout)
{
struct sockaddr_in address;
struct in_addr inaddr;
struct hostent *host;
int err, noblock=1 , connect_ok=0, begin_time=time(NULL);
log_debug("connect_socket to %s:%d\n",dest_host,port);
if (inet_aton(dest_host, &inaddr))
{
// log_debug("inet_aton ok now gethostbyaddr %s\n",dest_host);
memcpy(&address.sin_addr, &inaddr, sizeof(address.sin_addr));
}
else
{
log_debug("inet_aton fail now gethostbyname %s \n",dest_host);
host = gethostbyname(dest_host);
if (!host) {
/* We can't find an IP number */
log_error("error looking up host %s : %d\n",dest_host,errno);
return -1;
}
memcpy(&address.sin_addr, host->h_addr_list[0], sizeof(address.sin_addr));
}
address.sin_family = AF_INET;
address.sin_port = htons(port);
/* Take the first IP address associated with this hostname */
ioctl(sockfd,FIONBIO,&noblock);
/** connect until timeout */
/*
EINPROGRESS A nonblocking socket connection cannot be completed immediately.
EALREADY The socket is nonblocking and a previous connection attempt has not been completed.
EISCONN The socket is already connected.
*/
if (connect(sockfd, (struct sockaddr *) &address, sizeof(address)) < 0)
{
err = errno;
if (err != EINPROGRESS)
{
log_error("connect = %d connecting to host %s\n", err,dest_host);
}
else
{
// log_notice("connect pending, return %d \n", err);
while (1) /* is noblocking connect, check it until ok or timeout */
{
connect(sockfd, (struct sockaddr *) &address, sizeof(address));
err = errno;
switch (err)
{
case EISCONN: /* connect ok */
connect_ok = 1;
break;
case EALREADY: /* is connecting, need to check again */
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