c - How do I change a TCP socket to be non-blocking?

Question

How do you make a socket non-blocking?

I am aware of the fcntl() function, but I've heard it's not always reliable.

Answer 1

fcntl() has always worked reliably for me. In any case, here is the function I use to enable/disable blocking on a socket:

#include <fcntl.h>

/** Returns true on success, or false if there was an error */
bool SetSocketBlockingEnabled(int fd, bool blocking)
{
   if (fd < 0) return false;

#ifdef _WIN32
   unsigned long mode = blocking ? 0 : 1;
   return (ioctlsocket(fd, FIONBIO, &mode) == 0) ? true : false;
#else
   int flags = fcntl(fd, F_GETFL, 0);
   if (flags == -1) return false;
   flags = blocking ? (flags & ~O_NONBLOCK) : (flags | O_NONBLOCK);
   return (fcntl(fd, F_SETFL, flags) == 0) ? true : false;
#endif
}