TCP File Transfer behind NAT

Dear All,

Can anyone tell me, how to write such a program that can transfer
files (either binary or text) behind NAT devices( such as for
computers behind firewalls and routers and other NAT devices) using
TCP socket programming.

I have a mechanism through which the public IP of the router and Port
number will be forwarded to me. But after that I am not sure that
simple TCP/IP socket programming will suffice or I need to do
something more for that.

If you have any article link or article or any example that shows how
the File Transfer can be done for such a case then please help me
regarding this.

Any sought of help or idea will be appreciated from you all.

from-
Saurabh Srivastava