Basic concept in the following WCF article

Question

I am a bit confused with this paticular blog post here... http://bartdesmet.net/blogs/bart/archive/2006/09/13/4417.aspx

What is his concept of tunelling? I mean how is he able to access port 110 on WCF client through HTTP from the WCF server?

I don't get that part.

Thanks.

Edit : I understand the fact that he's creating a pop3 client on the WCF server and pop3 server on the WCF client. But,how is he accomplishing the VPN part? 110 without NAT? How?

Answer 1

What he has done is created a WCF client that implements the pop3 protocol and a WCF server that also implements the pop3 protocol. The WCF client can communicate to the server using plain old HTTP which is allowed by most firewals. So now the way it works is his mail client talks to the WCF client using pop3 both on localhost so that it can access port110 regardless of the firewall settings of the network he is on. The WCF client talks to the WCF server using HTTP. The WCF server (which is on a network that allows accessing port 110) talks to the original pop3 server he is trying to get mail from using POP3. There is no NAT or VPN involved. If it's not clear add a comment and I will try to expand.