title: How to open UDP port with iptables in linux
body: <p>Im playing around with my raspberry pi and i have a music box running (with mopidy). on addition to this i want to realize some other fancy stuff. i want to send a (UDP?)-Message from my Smartphone (With Tasker) to my PI. But i get always a "Connection Refused"-Message. I tried to open any UDP/TCP Port in iptables. 
  To receive the messages i tried 
  <code>netcat -ul 222</code></p>
  
  <p>for editing iptables im using:
  <code>sudo nano /etc/network/iptables</code>
  <code>sudo iptables-restore /etc/network/iptables</code>
  <code>sudo iptables-save</code>
  to see what ports are open im using:
  <code>netstat -tuplen</code>
  but i dont know what i have to expect on this output to realize my thing. am i on the right way or am i completely wrong :-) ?
  finally i want to receive any messages to translate it to any other action (for exampe <code>reboot</code>)
  thanks in advance!</p>