-# On creation, it binds to `localhost` with an OS-assigned TCP port. It writes
-# the decimal TCP port number to a temporary port file. It renames the
-# temporary port file to `port_filename`.
+# On creation, it binds to `localhost` on the TCP port `port` if not `None`, or
+# on an OS-assigned TCP port otherwise. It writes the decimal TCP port number
+# to a temporary port file. It renames the temporary port file to
+# `port_filename`.