title: How do Twisted python Factory and Protocol interfaces work?
body: <p>I am learning Twisted, and beginner's <a href="http://krondo.com/?page_id=1327" rel="noreferrer">tutorial</a> often uses Factory and Protocol as examples. It appears that Factory and <a href="http://twistedmatrix.com/trac/browser/tags/releases/twisted-12.3.0/twisted/internet/interfaces.py" rel="noreferrer">Protocol</a> interfaces do not support sending messages. Is it expected that sending messages are implemented independently of Protocol interface?  </p>
  
  <pre><code>class IProcessProtocol(Interface):
      def makeConnection(process):
      def childDataReceived(childFD, data):
      def childConnectionLost(childFD):
      def processExited(reason):
      def processEnded(reason):
  </code></pre>