port_string

Returns a string port suffix, including colon, like “:8080” if the port number of this request is not the default HTTP port 80 or HTTPS port 443.

req = ActionDispatch::Request.new 'HTTP_HOST' => 'example.com:80'
req.port_string # => ""

req = ActionDispatch::Request.new 'HTTP_HOST' => 'example.com:8080'
req.port_string # => ":8080"