People can connect to bnet in the first place because....you have to do nothing to get on battlenet. You don't have to forward any ports at all unless you want to host a game. So it doesn't have the inherant problems that DG has. Also the host/client network doesn't have the problems of p2p with some ISPs limiting it and whatnot.
List checker doesn't do any pairing. It's a program you run instead of using WC3 to connect to battlenet. It puts your game on battlenets list of games. People join the game. The same as anyone hosting it through other methods. LC doesn't do anything ouside of placing your game on battle net for people to join then running the game as if it were on your LAN (EG: With less lag than battlenet adds to the game)
Again, this is all moot if you take the time to use banlist and look at peoples country of origin as well as their ping. In my games anyone outside of the US/CA or with pings over 150 are kicked.
From List Checker's site
this will allow you to host a game in LAN mode (with low latency) and to have it in battlenet's games list
From WinPCap's site (needed to run List checker)
WinPcap is the industry-standard tool for link-layer network access in Windows environments: it allows applications to capture and transmit network packets bypassing the protocol stack, and has additional useful features, including kernel-level packet filtering, a network statistics engine and support for remote packet capture.
WinPcap consists of a driver, that extends the operating system to provide low-level network access, and a library that is used to easily access the low-level network layers. This library also contains the Windows version of the well known libpcap Unix API.
