TCP File Transfer behind NAT

[Saurabh]

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

 

[Kenneth P. Turvey]

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.

[Snip]

The only real issue here is that the computer behind the firewall must
open all the TCP connections. Now if both computers are behind their own
firewalls, then you may have a problem. You will have to look at using
something like a SIP server in that case.

 

[Roedy Green]

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

If you are allowed to program the router to let the traffic through,
your code is unaware there ever was a firewall blocking it. There is
nothing to do. All the tricky stuff is in the firewall, perhaps
remapping ports from public to private.