Hello World

This is a very common problem faced by users all over when they have
their home pc which has an IP not accessible from the Internet.
Similarly there is another computer eg. a friends or even the company
computer that is not accessible from the Internet.

In short, both computers even though having Internet access (can access
websites/ftp/public ip addresses) but cannot directly talk to each
other as they have private IP addresses on their own local networks.

How can these two computers talk to each other over the Internet. eg..
if the home computer wants to access the VNC server running on the
friends/company's computer, how could this work assuming we don''t want
to involve any changes to the routers/firewalls by allowing port

Tricky?? I'm stumped.