how can an application use port 80/HTTP without conflicting with browsers?

Question

If I understand right, applications sometimes use HTTP to send messages, since using other ports is liable to cause firewall problems. But how does that work without conflic

Answer 1

Outgoing HTTP requests don't happen on port 80. When an application requests a socket, it usually receives one at random. This is the Source port.

Port 80 is for serving HTTP content (by the server, not the client). This is the Destination port.

Each browser uses a different Source to generate requests. That way, the packets make it back to the correct application.