UPnP #114

Finally a seemingly proper patch for UPnP Port Mapping. Note that this one still does not have proper support in the makefiles for anything but UNIX.

Cool! Thanks for being persistent.

Two comments:

The appropriate copyright notice should be added to uiproject.fbp and uibase.cpp; I think building the next release with UpNP support compiled in would be a good idea.

Having both -noupnp and -upnp options (and tri-state USE_UPNP) is confusing and will cause problems if bitcoin.conf files are copied around. I'd suggest something like (assuming we want upnp on by default for Windows):

bool fUseUpnp = GetBoolArg("-upnp");
#ifdef _WINDOWS
if (mapArgs.count("-upnp") == 0)
    fUseUpnp = true;  // upnp on if not explicitly turned off
#endif

Didn't realize Luke added -upnp in his commit, sorry. The original intention was to have USE_UPNP as a compile option as to whether or not one would compile with UPnP or not and a single -noupnp where UPnP defaults to on.
Currently the Windows makefile doesn't support any UPnP (some have suggested using Window's native UPnP library instead on Windows). I think it should be always on by default. In the end that can only be better for the network as it creates more peer diversity (and maybe eventually increasing MAX_OUTBOUND_CONNECTIONS). I will do that unless you disagree.

Please start a discussion on the forums about whether or not UpNP should be on or off by default; I think you will find strong feelings that it should be off by default among Linux folks.

Forum thread here: http://www.bitcoin.org/smf/index.php?topic=4392.0

Consensus seems to be "off by default"

That's the interesting thing about UPnP, for an individual, having UPnP on by default is bad - potential security problems down the line, increased traffic, etc. For the network as a whole, having UPnP on by default is good as it creates more nodes which accept incoming connections ie good for network diversity in the long run. (maybe even increased MAX_OUTBOUND_CONNECTIONS in the future)