Is there a network ID for host among LAN?

Question

A router exposes itself to outside by IP like 66.249.89.104 and many hosts can connect to it to form a Local Area Network.

My question :

Is there a way to identify a specific host in that LAN?

All I tried is some guessing work which fails with no doubt:

ping [email protected]
Ping request could not find host [email protected]. Please check the name and try again.

I think since each host in LAN can get their packets from outside the router,there MUST be a way to identify each host,but what's that?

UPDATE How to achieve Port forwarding except configuring it in the router?

UPDATE

Now I think UPnP is the way to go,but is there a working sample for this?