Hi,
i have a question mark in my head about router...

i am planning to build a network in my house. Using a broadband router...to connect to my 2 pc...based on what i know...the ISP will assign the router an IP and the router would run a DHCP to assign my 2 PCs in the LAN...

1. In the case above, is my router in a firewall position?If yes then how how does a hacker hack to my PC behind the router?

2. I have been doing a chatting program for fun using Java, how to i experiment it with my friend in the net with the router?