Ports and Services

Transport protocols use port numbers to distinguish applications on the same host.

A listening port means a process is waiting for connections on an interface. Firewalls, routing and access-control rules still determine whether other systems can reach it.

Defensive checks

In Termux, inspect local listeners with:

ss -lntup

A service should listen only where needed, run with minimal privileges and receive security updates. Port scanning is performed only against systems you own or are explicitly authorized to assess.