Scope

trop coordinates port numbers for processes using the same reservation database. The intended setup is one user account on one machine.

What a reservation means

While a reservation exists, ordinary calls for the same directory and tag return its stored port. Another key in the same database cannot reserve that number. This also applies to concurrent callers.

The reservation is for a port number, without a separate allocation for each protocol or interface. By default, new allocations check TCP and UDP on IPv4 and IPv6 localhost and skip occupied or excluded ports.

Limits

• No socket is held open. Another program can bind the port after the occupancy check. Reusing an existing reservation returns its stored number without a fresh occupancy check; your server can still fail to bind.
• Separate databases do not coordinate. Other users, hosts, or callers with a different --data-dir can choose the same number.
• The mapping lasts as long as the record. Releasing, pruning, expiring, or explicitly overwriting a reservation can change its port on the next call.
• Process lifetime is separate. trop does not start, stop, or monitor your servers. Two servers using the same directory and tag will receive the same port.

For reservation removal, see cleanup commands.