Where (in what line of business) is network programming used primarily used?

"Open, Web, Embedded" I use it when I use it in any genre, but it's rare not to use it.
Even old games such as PS2 used to be used in some parts, so I think it's more unusual if you don't use them now.If your network programming is limited to using the Internet, I can narrow it down a little bit, but on the contrary, isn't it more difficult to find products that can't connect to the Internet these days?
Even the refrigerator is connected to the Internet...

Few systems are configured with standalone systems.
Assuming a three-tier Web server, the AP and DB servers are typically configured to be separate instances, but the AP and DB servers are meaningless in the first place with standalone.Use with a NETWork connection.
So if you're aware of TCP/IP when you connect, then the application layer protocol hides the communication procedure.You can think of it as "not a network program," but it's hidden after all, and someone is controlling another protocol at the bottom.
Conversely, transport layer protocols are rarely used directly.

It is used where communication takes place.Some of my experiences include:

• Digital cameras and printers communicate with your PC via wifi
• Network Attached Storage (NAS) communicates with other devices in the LAN
• One device with defense equipment communicates with another device (TCP or UDP)

For this stackoverflow, HTTPS is at the top of the network layer, but TCP is used when it goes down to the bottom.

It is used in a variety of industries, regardless of whether it is open, web, or embedded.
Rather, I think there are fewer areas that are not involved in network programs.