winsock transfer file through nat

I am using vb6 and winsock to transfer files , Some of our customers use it to send files to us and we send a file back automaticaly.


Some of the customers have a internet router which uses nat then it does not work. You have to add a static route from internet to the ip address of the pc on the network for it to work.


i have added a static route for us but cannot expect all our customers to do this.

Can this be overcome with programing. are there any code samples ,web pages ?

thankls for any help Nicholas

I think the router which use nat technology can transfer the data package from internal ip address to external ip address automatically.If your software use the fixed ip in the communication period,u must change the ip which at the internal to external!..But it need add static route??

If my pc is on a modem and the remote one is on a network which has a broadband router giving there network internet access.


if i use

frmchat.tcpsocket.Connect remoteipaddress, 21

it cannot connect to it as they have a internet IP address and then local ip addresses on there lan.

if you connect to someone with only a modem connection then there internet ip is on there pc so it will connect.

How do you connect in this situation. FTP programs,msn messenger , icq gets over this. ???

Nick

I think the NAT function of the broadband router is transparent to internal users.If u can access internet web site and the network manager permit u to access internet ip ftp,u must can do it!U can try to input these command in the console windows:
ftp xxx.xxx.xxx.xxx
note:xxx.xxx.xxx.xxx is the internet ip,as ftp.microsoft.com...Good luck!

Usually there is a way to set up the NAT router to forward ports. For example, in a low-end Linksys DSL router there is a Forwarding page in the setup where can identify the port number you want to allow, and designate an internal IP as the desired destination.