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

Port 80 you're talking about here is the remote port on the server, locally browser opens high port for each connection established.

Each connection has port numbers on both ends, one is called local port, other remote port.

Firewall will allow traffic to high port for browser, because it knows that connection has been established from you computer.