I'm trying to use libmicrohttpd on a platform where fcntl(fd, O_NONBLOCK)

doesn't work for sockets. This shouldn't be a problem, as far as I understand,
except in epoll mode, which I'm not using, because epoll() isn't available either.

However, there is a check in daemon.c:internal_add_connection(),
the purpose of which seems to be to prevent using a blocking socket
in epoll mode. At least that's what the debug message says. The code
however does the opposite, it prevents the use of a blocking socket
if epoll mode is *not* used. This was probably never noticed because
platforms without non-blocking sockets are rare.

Please consider applying the following simple fix:

src/microhttpd/daemon.c

@@ -2985,7 +2985,7 @@ internal_add_connection (struct MHD_Daemon *daemon,
     return MHD_NO;
   }
 
-  if ( (0 == (daemon->options & MHD_USE_EPOLL)) &&
+  if ( (0 != (daemon->options & MHD_USE_EPOLL)) &&
        (! non_blck) )
   {
 #ifdef HAVE_MESSAGES