File transfer over WAN using sockets

[Chris Brat]

Hi all,
Have written a small client app to transfer a text file to a server running on another pc in the LAN...
This works beautifully!! Not that difficult to do over a LAN right ?
So My concerns deal with WAN communication...
- What security issues must i cater for (like firewalls) and how do I do that ?
- If my server app will be running in another building on its own LAN of 5 pcs, how do i differentiate it from the other 4 pcs...
In my LAN all i had to do was specify the IP address and port and didnt have to worry about firewalls, user authentication or subnet-masks... Do I have to now with the WAN?
Thanks
Chris

[Raghav Mathur]

can you please elaborate your query