code to solve "SOCK_NONBLOCK" and "O_NONBLOCK" undefined problem in linux

#if defined(SOCK_NONBLOCK)

return ::socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);

/* If they have O_NONBLOCK, use the Posix way to do it */

#elif defined(O_NONBLOCK)

/* Fixme: O_NONBLOCK is defined but broken on SunOS 4.1.x and AIX 3.2.5. */

int sock = socket(PF_INET, SOCK_STREAM, 0);

int flags;

if (-1 == (flags = fcntl(sock, F_GETFL, 0)))

flags = 0;

fcntl(sock, F_SETFL, flags | O_NONBLOCK);

return sock;

#else

int sock = socket(PF_INET, SOCK_STREAM, 0);

/* Otherwise, use the old way of doing it */

int flags = 1;

ioctl(sock, FIOBIO, &flags);

return sock;

#endif