Here's some documentation example code of how to create a TCP client in C# if you decide to go the TCP/Sockets route over WCF: http://www.winsocketdotnetworkprogramming.com/clientserversocketnetworkcommunication8q.html
And here's the MSDN page on WCF: https://msdn.microsoft.com/en-us/library/ms731082(v=vs.110).aspx
This is the MSDN page on creating a service application: https://msdn.microsoft.com/en-us/library/zt39148a(v=vs.110).aspx
Do note: "The Windows Services project template that is required for this walkthrough is not available in the Express edition of Visual Studio."
But don't let that concern you. All this means is that your program would not be able to register as a windows service, and therefore could not truly operate like a service which can start on boot, pause, stop restart, etc. Howerver, this doesn't stop you from creating a program that automatically starts. You could simply place a shortcut to your program in your startup folder:
C:\Users\Username\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
Hopefully that helps get you started in the right direction!