Module: Portless::FreePort

Defined in:
lib/portless/free_port.rb

Overview

Picks a free backend port for an app (4000-4999). Random-first to keep the check→bind race window small, skipping the WHATWG bad-port set so browsers never refuse the URL. Mirrors portless's findFreePort.

Constant Summary collapse

RANDOM_ATTEMPTS = 
50

Class Method Summary collapse

Class Method Details

.available?(port) ⇒ Boolean

Truly free = we can bind it right now on loopback. (TOCTOU inherent, same as portless; random-first mitigates.)

Returns:

  • (Boolean) 


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# File 'lib/portless/free_port.rb', line 31

def available?(port)
  server = TCPServer.new("127.0.0.1", port)
  server.close
  true
rescue Errno::EADDRINUSE, Errno::EACCES
  false
end

.find ⇒ Object

Raises:



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# File 'lib/portless/free_port.rb', line 14

def find
  RANDOM_ATTEMPTS.times do
    port = rand(Constants::MIN_APP_PORT..Constants::MAX_APP_PORT)
    next if Constants::BLOCKED_PORTS.include?(port)
    return port if available?(port)
  end

  (Constants::MIN_APP_PORT..Constants::MAX_APP_PORT).each do |port|
    next if Constants::BLOCKED_PORTS.include?(port)
    return port if available?(port)
  end

  raise Error, "no free port available in #{Constants::MIN_APP_PORT}-#{Constants::MAX_APP_PORT}"
end