Your confusion lies in thinking that a socket is identified by Server IP : Server Port. When in actuality, sockets are uniquely identified by a quartet of information:
Client IP : Client Port and Server IP : Server Port
So while the Server IP and Server Port are constant in all accepted connections, the client side information is what allows it to keep track of where everything is going.
Example to clarify things:
Say we have a server at 192.168.1.1:80 and two clients, 10.0.0.1 and 10.0.0.2.
10.0.0.1 opens a connection on local port 1234 and connects to the server. Now the server has one socket identified as follows:
10.0.0.1:1234 - 192.168.1.1:80
Now 10.0.0.2 opens a connection on local port 5678 and connects to the server. Now the server has two sockets identified as follows:
10.0.0.1:1234 - 192.168.1.1:80
10.0.0.2:5678 - 192.168.1.1:80
The key decision is whether or not to make the WCF service conform to the socket client or whether to make the socket client conform to the WCF service.
It will be simplest to attempt to conform to the WCF service, rather than trying to implement something custom within WCF, which is never easy. At the bottom of the Other Resources section below you will see a link that describes the message inspection that is necessary in order to attempt to conform to a WCF service.
Having said that, .NET sockets do not natively communicate with WCF.
Any attempt to do so will require custom programming on the WCF side of things.
Whether you are using TcpClient or raw sockets in .NET to connect to and communicate with WCF does not matter. Any such interoperability must be handled with custom logic within WCF. Note that Net.Tcp is a custom transport protocol. It is not technically using TCP in the same way that the TcpClient is.
For example, UDP is very commonly used by socket servers in the Linux world. WCF does not provide a built-in UDP transport. However, there is a UDP sample for WCF that implements UDP for WCF. Unfortunately, that sample does not illustrate communicating to and from a non-WCF UPD socket server.
I have an outstanding question that is rather detailed where I explain my effort to get sample code to generically be testable for using UDP...
Is it possible to make the WcfTestClient work for custom transport channels?
Nobody has answered my question yet. So, if you succeed in making this work, I am very interested. My case was driven by a desire for the WCF Service to be able to call out to a UDP socket server running on Linux without having to clutter my service with non-WCF coding. I don't want to mix approaches.
Other Resources...
Best Solution
I think you are looking for this - How to use socket based client with WCF (net.tcp) service?
The way I see it you want to feed from wcf service with a socket object (correct me if I got it wrong)... I haven't done it (just read it)