Callback to client behind a NAT / Firewall

Hi
how to Callback to client behind a NAT / Firewall?
like messangers and other programs that call client behind NAT
any example?

by the way messangers works fine without opening ports on te router.

thanks in advance.

Most programs don't "call back" to the client. Instead the client maintains a connection to the server as long as it is running/logged on.

There are exceptions using various techniques but they don't always work.

http://en.wikipedia.org/wiki/NAT_traversal

This is a NAT issue, with little to do with firewalls. If a firewall is going to block traffic you'll never get around it unless the firewall is faulty.

To enable NAT-T for systems behind NATs to communicate with other systems behind NATs, the following registry key needs to be added and set to a value of 2: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\IPsec\AssumeUDPEncapsulationContextOnSendRule

if i make this key and set it to 2 i will be ablle to connect with machines behind LAN?

thanks in advance.