t.f.protocol : module documentation

Construct a flow based protocol

This takes a base protocol class, and a set of callbacks and creates a connection flow based on the two. For example, the following would build a simple 'echo' protocol:

   from __future__ import generators
   from twisted.internet import reactor, protocol
   from twisted.flow import flow
   PORT = 8392

   def echoServer(conn):
       yield conn
       for data in conn:
           conn.write(data)
           yield conn

   def echoClient(conn):
       conn.write("hello, world!")
       yield conn
       print "server said: ", conn.next()
       reactor.callLater(0,reactor.stop)

   server = protocol.ServerFactory()
   server.protocol = flow.makeProtocol(echoServer)
   reactor.listenTCP(PORT,server)
   client = protocol.ClientFactory()
   client.protocol = flow.makeProtocol(echoClient)
   reactor.connectTCP("localhost", PORT, client)
   reactor.run()

Of course, the best part about flow is that you can nest stages. Therefore it is quite easy to make a lineBreaker generator which takes an input connection and produces and output connection. Anyway, the code is almost identical as far as the client/server is concerned:

   # this is a filter generator, it consumes from the
   # incoming connection, and yields results to
   # the next stage, the echoServer below
   def lineBreaker(conn, lineEnding = "\n"):
       lst = []
       yield conn
       for chunk in conn:
          pos = chunk.find(lineEnding)
          if pos > -1:
              lst.append(chunk[:pos])
              yield "".join(lst)
              lst = [chunk[pos+1:]]
          else:
              lst.append(chunk)
          yield conn
       yield "".join(lst)

   # note that this class is only slightly modified,
   # simply comment out the line breaker line to see
   # how the server behaves without the filter...
   def echoServer(conn):
       lines = flow.wrap(lineBreaker(conn))
       yield lines
       for data in lines:
           conn.write(data)
           yield lines

   # and the only thing that is changed is that we
   # are sending data in strange chunks, and even
   # putting the last chunk on hold for 2 seconds.
   def echoClient(conn):
       conn.write("Good Morning!\nPlease ")
       yield conn
       print "server said: ", conn.next()
       conn.write("do not disregard ")
       reactor.callLater(2, conn.write, "this.\n")
       yield conn
       print "server said: ", conn.next()
       reactor.callLater(0,reactor.stop)