freeport-async

Finds an available port for your application to use. You can specify a range where to look for an available port. And can also find a range of available ports for you to use. You can also be used to test to see if a given port is available.

All functions are async and return Promises.

Usage

Basic

let freeportAsync = require("freeport-async");

let portICanUse = await freeportAsync();

Advanced

let freeportAsync = require("freeport-async");

let portIn9000Range = await freeportAsync(9000);

let portAvailableForAnyOrLocalhost = await freeportAsync(9000, {
  hostnames: [null, "localhost"]
});

let isPort5000Available = await freeportAsync.availableAsync(5000);

let listOf5ConsecutiveAvailablePorts = await freeportAsync.rangeAsync(5);

let freeRangeIn12000Range = await freeportAsync.rangeAsync(3, 12000);

Important Note

Note that this code just finds available ports, but doesn't reserve them in any way. This means that if you have other code that might be looking for a port in the same range at the same time, you could run into issues.

Also, if you call freeportAsync twice in a row, it will often return the same port number twice. If you want to find two (or more) ports you can use, you need to call freeportAsync.rangeAsync(<number-of-ports>, [startSearchFrom]).

See also https://gist.github.com/mikeal/1840641