   detecting if a set of ports are open
  Any easy way to detect if a specific port can be opened by an application? In other words, what would be the best way to detect if the ports / application are blocked by firewalls? (Windows XP / Vista / Win 7).The obvious answer is that if you can communicate to your server, then it's opened! Then the easy solution is to provide a troubleshooting guide on making the game work over the internet, but for convenience, it would be interesting if the potential problems can be detected at the source reliably. Cheers.   
  Can't you just bind the port in question and connect/send a datagram to it? If it works the port is open.   ;  was thinking of sending and receiving to loopback address, but dunno how the routing to loopback is actually handled by routers and firewalls.   ;Quote:Original post by oliiiwas thinking of sending and receiving to loopback address, but dunno how the routing to loopback is actually handled by routers and firewalls.I would avoid the loopback interface; it probably won't even pass through the NIC, let alone a firewall. Get the local (as in LAN) IP address of the computer and connect/send to it instead.   ;  There's an IFwAdmin interface where you can specifically check this (and change it, if needed). Unfortunately you'll need administrator privileges to use it. Hence, most Windows applications will open the ports they need in the installer, which is generally run with administrator privileges.