How to find the local port a rails instance is running on?

Question

So I would like my Rails app instances to register themselves on a "I'm up" kind of thing I'm playing with, and I'd like it to be able to mention what local port it's running on. I can't seem to find how to do it - in fact just finding out its IP is tricky and needs a bit of a hack.

But no problem, I have the IP - but how can I find what port my mongrel/thin/webrick server is running on?

To be super explicit, if I start a rails app using script/server -p 3001, what can I do to pull that 3001 inside the app.

Whereabouts are you putting the code which does the registering? — mikej, Oct 12 '09 at 12:57
I would like it to be in an initializer but it could be anyway really. The important thing is it's able to announce itself to another machine - "hi, i was started on port #{PORT}" - where port could be anything. Basically, Rails equivalent to Sinatra::Application.port. — RailFan, Oct 12 '09 at 18:05
Most answers to the hostname question also answer this: http://stackoverflow.com/questions/42566/getting-the-hostname-or-ip-in-ruby-on-rails — Ciro Santilli OurBigBook.com, Oct 09 '14 at 20:36

score 21 · Answer 1 · answered Dec 12 '12 at 12:07

21

You can call Rails::Server.new.options[:Port] to get the port that your Rails server is running on. This will parse the -p 3001 args from your rails server command, or default to port 3000.

answered Dec 12 '12 at 12:07

ndbroadbent

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This will work in the initialiser as it doesn't depend on the request object. – superluminary May 20 '13 at 09:53
4

`(rdb:1) Rails::Server *** NameError Exception: uninitialized constant Rails::Server` – zuba Mar 06 '14 at 13:20
3

Try `Rack::Server.new.options[:Port]` in newer versions of Rails – asgeo1 Jul 29 '15 at 08:48
3

`Rack::Server.new.options[:Port]` always returns 9292 – golfadas May 04 '17 at 08:21
I found `Rack::Server.new.options[:Port]` return the port if specified with '-p' option (Rails 5.1.1). – hiroshi Jul 12 '17 at 02:20

Lars Haugseth · Answer 2 · 2009-10-12T13:47:05.410

15

From inside any controller action, check the content of request.port, thus:

class SomeController < ApplicationController
  def some_action
    raise "I'm running on port #{request.port}."
  end
end

edited Oct 12 '09 at 13:47

answered Oct 12 '09 at 13:16

Lars Haugseth

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So simple and so easily overlooked. I thought about this for a few minutes and was thinking out round about ways of getting it. This question is a good reminder for me to review request again. http://api.rubyonrails.org/classes/ActionController/AbstractRequest.html – Jim Oct 12 '09 at 14:44
Precise for localhost, but does not work when behind an Apache Server or in a cluster setup. – Swanand Oct 12 '09 at 17:28
Thanks for the answer. Do you have any idea how to access that programmatically, ie something I can do inside script/console? After all, if I need to access it via HTTP, that means I already know the port! – RailFan Oct 12 '09 at 17:55

score 11 · Answer 3 · answered May 20 '13 at 09:59

11

Two ways.

If you're responding to a request in a controller or view, use the request object:

request.port

If you're in an initialiser and don't have access to the request object use the server options hash:

Rails::Server.new.options[:Port]

answered May 20 '13 at 09:59

superluminary

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`(rdb:1) Rails::Server *** NameError Exception: uninitialized constant Rails::Server` – zuba Mar 06 '14 at 13:20
@zuba, that's interesting. Did that occur in your initializer? – superluminary Mar 06 '14 at 13:22
Sorry, no, that occured in my controller rspec test debug console – zuba Mar 06 '14 at 17:21
3

You may have to require the appropriate library first. `require 'rails/commands/server'` – Seth Jeffery Oct 27 '14 at 10:02
@SethJeffery, it worked, but i have a little warning: By requiring rails server commands, you can't pass arguments to cucumber/rspec because the rails server launcher will raise an exception claiming that he got wrong arguments. – MhdSyrwan Apr 02 '15 at 09:17

score 9 · Answer 4 · answered Jan 03 '18 at 01:09

9

I played around with this a bit, and this might be the best solution for Rails 5.1:

Rails::Server::Options.new.parse!(ARGV)[:Port]

answered Jan 03 '18 at 01:09

jfly

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it returns `nil` when no explicit port specified – x'ES Oct 22 '20 at 20:34

score 6 · Answer 5 · answered Oct 12 '18 at 18:12

Building on the other answers (which saved my bacon!), I expanded this to give sane fallbacks:

In development:

port = Rails::Server::Options.new.parse!(ARGV)[:Port] || 3000 rescue 3000

In all other env's:

port = Rails::Server::Options.new.parse!(ARGV)[:Port] || 80 rescue 80

The rescue 80 covers you if you're running rails console. Otherwise, it raises NameError: uninitialized constant Rails::Server. (Maybe also early in initializers? I forget...)

The || 80 covers you if no -p option is given to server. Otherwise you get nil.

hiroshi · Answer 6 · 2017-07-12T03:00:27.290

5

For Rails 5.1 development server.

if Rack::Server.new.options[:Port] != 9292 # rals s -p PORT
  local_port = Rack::Server.new.options[:Port]
else
  local_port = (ENV['PORT'] || '3000').to_i # ENV['PORT'] for foreman
end

edited Jul 12 '17 at 03:00

answered Jul 12 '17 at 02:26

hiroshi

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How to find the local port a rails instance is running on?

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