Ruby on Rails - Address already in use - bind(2) for "0.0.0.0" port 3000 (Errno::EADDRINUSE)

Question

When I attempt to start my rails server from my local machine, I get the following error message.

/Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:269:in `initialize': Address already in use - bind(2) for "0.0.0.0" port 3000 (Errno::EADDRINUSE)
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:269:in `new'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:269:in `add_tcp_listener'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:105:in `block in parse'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:88:in `each'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/binder.rb:88:in `parse'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/runner.rb:144:in `load_and_bind'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/cluster.rb:391:in `run'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/puma/launcher.rb:174:in `run'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/puma-3.9.1/lib/rack/handler/puma.rb:69:in `run'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/rack-2.0.3/lib/rack/server.rb:297:in `start'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands/server.rb:104:in `start'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:90:in `block in server'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:85:in `tap'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:85:in `server'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/railties-5.0.3/lib/rails/commands.rb:18:in `<top (required)>'
from /Users/zachdobbs/sample_app/bin/rails:9:in `require'
from /Users/zachdobbs/sample_app/bin/rails:9:in `<top (required)>'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/zachdobbs/.rbenv/versions/2.4.0/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/zachdobbs/sample_app/bin/spring:15:in `<top (required)>'
from bin/rails:3:in `load'
from bin/rails:3:in `<main>'

This error occurred suddenly and I'm not sure what the cause of it could be. When I looked online I noticed that the issue could be another service running on the port 3000, but when I try and run 'lsof -i tcp:3000' I get no results.

Within puma.rb, I define.

port        ENV.fetch("PORT") { 3000 }
rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'

When I change the port value to something such as 8080 the server will run. I am confused as to why the server will not launch on port 3000. Every command I have attempted to run has shown me no services running on that port.

Answer 1

I know this is a really old post but I had to answer just in case others get here as I did.

When you declare port or bind commands in the puma config it will try to bind to all those ports or addresses.

In this case you've specified port twice so it's trying to bind to both and the second one will fail.