port-for is a command-line utility and a python library that
helps with local TCP ports management.
It can find an unused TCP localhost port and remember the association:
$ sudo port-for foo 37987
This can be useful when you are installing a stack of software with multiple parts needing port numbers.
If you're looking for a temporary port then
is your best bet:
>>> import socket >>> s = socket.socket() >>> s.bind(("", 0)) >>> s.getsockname() ('0.0.0.0', 54485)
port-for is necessary when you need persistent free local port number.
port-for is the exact opposite of
in the sense that it shouldn't return ports that
may return (because such ports are likely to be temporary used by OS).
There are several rules
port-for is trying to follow to find and
return a new unused port:
- Port must be unused:
port-forchecks this by trying to connect to the port and to bind to it.
- Port must be IANA unassigned and otherwise not well-known: this is acheived by maintaining unassigned ports list (parsed from IANA and Wikipedia).
- Port shouldn't be inside ephemeral port range.
This is important because ports from ephemeral port range can
be assigned temporary by OS (e.g. by machine's IP stack) and
this may prevent service restart in some circumstances.
port-fordoesn't return ports from ephemeral port ranges configured at the current machine.
- Other heuristics are also applied:
port-fortries to return a port from larger port ranges; it also doesn't return ports that are too close to well-known ports.
System-wide using easy_install (something like
should be installed):
sudo pip install port-for
sudo easy_install port-for
or inside a virtualenv:
pip install port-for
port-for <foo> script finds an unused port and associates
<foo>. Subsequent calls return the same port number.
This utility doesn't actually bind the port or otherwise prevents the
port from being taken by another software. It tries to select
a port that is less likely to be used by another software
(and that is unused at the time of calling of course). Utility also makes
port-for bar won't return the same port as
on the same machine.
$ sudo port-for foo 37987 $ port-for foo 37987
You may want to develop some naming conventions (e.g. prefix your app names) in order to enable multiple sites on the same server:
$ sudo port-for example.com/apache 35456
Please note that
port-for script requires read and write access
/etc/port-for.conf. This usually means regular users can read
port values but sudo is required to associate a new port.
List all associated ports:
$ port-for --list foo: 37987 example.com/apache: 35456
Remove an association:
$ sudo port-for --unbind foo $ port-for --list example.com/apache: 35456
>>> import port_for >>> port_for.select_random() 37774 >>> port_for.select_random() 48324 >>> 80 in port_for.available_good_ports() False
Dig into source code for more.
Development happens at github: https://github.com/kmike/port-for/
Issue tracker: https://github.com/kmike/port-for/issues/new
In order to run tests make sure you have tox installed, then type
from the source checkout.