Ruby - See if a port is open

Question

I need a quick way to find out if a given port is open with Ruby. I currently am fiddling around with this:

require \'socket\'

def is_port_open?(ip, port)
          


        

Answer 1

All other existing answer are undesirable. Using Timeout is discouraged. Perhaps things depend on ruby version. At least since 2.0 one can simply use:

Socket.tcp("www.ruby-lang.org", 10567, connect_timeout: 5) {}

For older ruby the best method I could find is using non-blocking mode and then select. Described here:

• https://spin.atomicobject.com/2013/09/30/socket-connection-timeout-ruby/

Answer 2

Something like the following might work:

require 'socket'
require 'timeout'

def is_port_open?(ip, port)
  begin
    Timeout::timeout(1) do
      begin
        s = TCPSocket.new(ip, port)
        s.close
        return true
      rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH
        return false
      end
    end
  rescue Timeout::Error
  end

  return false
end

Answer 3

All *nix platforms:

try nc / netcat command as follow.

`nc -z -w #{timeout_in_seconds} -G #{timeout_in_seconds} #{host} #{port}`
if $?.exitstatus == 0
  #port is open
else
  #refused, port is closed
end

The -z flag can be used to tell nc to report open ports, rather than initiate a connection.

The -w flag means Timeout for connects and final net reads

The -G flag is connection timeout in seconds

Use -n flag to work with IP address rather than hostname.

Examples:

# `nc -z -w 1 -G 1 google.com 80`
# `nc -z -w 1 -G 1 -n 123.234.1.18 80`

Answer 4

My slight variation to Chris Rice's answer. Still handles timing out on a single attempt but also allows multiple retries until you give up.

    def is_port_open?(host, port, timeout, sleep_period)
      begin
        Timeout::timeout(timeout) do
          begin
            s = TCPSocket.new(host, port)
            s.close
            return true
          rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH
            sleep(sleep_period)
            retry
          end
        end
      rescue Timeout::Error
        return false
      end
    end

Answer 5

I recently came up with this solution, making use of the unix lsof command:

def port_open?(port)
  !system("lsof -i:#{port}", out: '/dev/null')
end

Answer 6

More Ruby idiomatic syntax:

require 'socket'
require 'timeout'

def port_open?(ip, port, seconds=1)
  Timeout::timeout(seconds) do
    begin
      TCPSocket.new(ip, port).close
      true
    rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH
      false
    end
  end
rescue Timeout::Error
  false
end