unfortunately a great number of domestic grade routers don't have properly working automatic port forwarding, and a large number of mobile providers don't give you an IP address, and even more of them don't give you IPv6 i have been saying this for years, the gigacorps don't want us to have p2p because we would discover that we don't need them. it would be one of the biggest industry shakeouts of history. they are shitscared