It's a simple Ruby gem to get a random TCP port.

First, install it:

$ gem install random-port

Then, use it like this, to reserve a random TCP port:

require 'random-port'
port = RandomPort::Pool.new.acquire

The Pool guarantees that the port won't be used again. You can put the port back to the pool after usage:

RandomPort::Pool.new.acquire do |port|
  # Use the TCP port. It will be returned back
  # to the pool afterwards.
end

You can do it without the block:

pool = RandomPort::Pool.new
port = pool.acquire
pool.release(port)

You can also use a pre-defined Pool::SINGLETON singleton:

RandomPort::Pool::SINGLETON.acquire do |port|
  # Use it here...
end

The pool is thread-safe by default. You can configure it to be not-thread-safe, using optional sync argument of the constructor.

How to contribute

Read these guidelines. Make sure you build is green before you contribute your pull request. You will need to have Ruby 2.3+ and Bundler installed. Then:

$ bundle update
$ bundle exec rake

If it's clean and you don't see any error messages, submit your pull request.