title: port in use when not using a port
body: <p>I'm trying to run the following Sinatra application and am getting an error message telling me that I can't start a server, either because port's already in use or because I don't have root privileges. I have never had this problem before starting a Sinatra application. I updated to Mountain Lion for my mac a few days ago and wonder if this might be the cause of the problem. I also use RVM.  Can anyone provide a suggestion...</p>
  
  <pre><code>require "sinatra"
  
  class MyApp &lt; Sinatra::Base
   get '/' do
      "Hello from MyApp"
  
   end
  
  end 
  
  == Sinatra/1.3.3 has taken the stage on 4567 for development with backup from Thin
  &gt;&gt; Thin web server (v1.5.0 codename Knife)
  &gt;&gt; Maximum connections set to 1024
  &gt;&gt; Listening on 0.0.0.0:4567, CTRL+C to stop
  /Users/me/.rvm/gems/ruby-1.9.2-p290@global/gems/eventmachine-1.0.0/lib/eventmachine.rb:526:in `start_tcp_server': no acceptor (port is in use or requires root privileges) (RuntimeError)
  </code></pre>
  
  <p>Update:
  I can still run a rails server on my machine so I think the problem is specific to Sinatra. Furthermore, I was able to run Sinatra applications fine up til a few days ago, when I started playing around with this  <a href="http://rubylearning.com/blog/a-quick-introduction-to-rack/" rel="noreferrer">Rack Tutorial</a>which instructed me to explicitly to set a port. I'm wondering if that made a permanent change. </p>
  
  <pre><code>&gt;&gt; Rack::Handler::WEBrick.run my_rack_proc, :Port =&gt; 9876
  [2011-10-24 11:32:21] INFO  WEBrick 1.3.1
  [2011-10-24 11:32:21] INFO  ruby 1.9.2 (2011-07-09) [i386-mingw32]
  [2011-10-24 11:32:21] INFO  WEBrick::HTTPServer#start: pid=480 port=9876
  </code></pre>