What are ports used for? For example, shop.r2.ru:8773 and shop.r2.ru:80 — can you access the same domain through different ports?

A port is a numerical identifier that allows the operating system to direct network traffic to the appropriate application or service on a single IP address.

For example, shop.r2.ru:80 refers to the domain on the standard HTTP port 80, while shop.r2.ru:8773 refers to the same domain but on a non-standard port, where another service might be running.

You can access the same domain through different ports, which means connecting to different services or applications running on those ports. This is often used to separate services (for example, a web server on 80, an API on 8080).

Thus, ports allow a single server to host multiple applications simultaneously, distinguishing them by port numbers.