Accessing a test client/server application through the internet

I'm testing my UWP application in C# using Visual Studio that sends images from a client app to the server app. I've set up the client and server on the local network on respective machines with IP's and ports and it works fine. I'm trying to test it now through the internet without the use of domain registering and web hosting etc. Is this possible? If so:

• What steps should I take to test this type of application (client/server model) through the internet?
• Could Windows Server be a solution? I have minimal experience with the OS.
• Can Apache handle this?