[Help] Does foreign IP matter when connecting to your server?

So, i have a friend from singapore whos trying to connect to my server, but after he enters his PIC he gets disconnected to login screen saying "unable to connect to server".

However, everyone else is able to connect just fine.

So i guess my question is, would there be some kind of "range IP" block that is somewhere compiled in the source im using that i need to change? or how would can this be fixed?

Thanks in advanced.

Your friend is probably connecting wrongly like his firewall deleted one of his files or the IP he enter-ed is invalid.

It's happening to me. I can't seems to pass thru' character place. Not only for foxtrot's server. I tried other server too, I Can't pass thru.