Ping your own gateway? Which? A server system could easily have more than one network card and complex network routing. Pinging some other site lets the system handle the choice of routes for you. Some will block it, yes, so just pick one that does not!

Try system() instead of popen(). The return value will be zero if connected to the net, nonzero if not. Also investigate the options for ping to limit the number of pings to one, and change the timeout to your preference:

Code:

if(system("ping -c 1 -w 1 yahoo.com > /dev/null 2> /dev/null") != 0)
  fprintf(stderr,"Net is down!\n");
else
  fprintf(stderr,"Net is up\n");

The file redirection just prevents ping from polluting the output with unnecessary stuff.

You could also open a network socket to, say, yahoo.com port 80. If you can do that, the net is up. Not as easy to configure timeouts for that though.