Twisted:
a quick introduction
Robert Coup
http://rob.coup.net.nz/

What?
http://twistedmatrix.com
“an event-driven networking engine
written in Python”

Networking?
• You name it, Twisted does it:
TCP, UDP, Telnet, SSH, SSL, HTTP, FTP,
SFTP, Gopher, XMPP, MSN, AIM, IRC,
Multicast, Unix, SMTP, LDAP, POP3,
NNTP, NTP, DNS...

Deferreds
• They’re the barrier to Twisted
• Single-threaded asynchronous programming
• A Deferred is a promise to call code later
• Not just a Python thing

twisted_deferred.py

Deferreds
from twisted.web.client import getPage
from twisted.internet import reactor
def printContents(contents):
'''
This is the 'callback' function, added to the Deferred and called by
it when the promised data is available
'''
print \"The Deferred has called printContents with the following
contents:\"
print contents
# Stop the Twisted event handling system -- this is usually handled
# in higher level ways
reactor.stop()

twisted_simple.py

Servers
from twisted.internet.protocol import Protocol, Factory
from twisted.internet import reactor
class QOTD(Protocol):
def connectionMade(self):
self.transport.write(\"An apple a day keeps the doctor away\\r\\n\")
self.transport.loseConnection()
# Next lines are magic:
factory = Factory()
factory.protocol = QOTD
# 8007 is the port you want to run under. Choose something >1024
reactor.listenTCP(8007, factory)
reactor.run()

Instant Messaging
• uses the Twisted Words project
• support for XMPP (Jabber) + AIM, ICQ,
MSN, IRC, …
• create a bot
• Wokkel makes it easier

Bot
• will connect to an XMPP server
• show itself as being online
• have a conversation with anybody who
talks to it

xmppClient.py

Manholes
• allow access into a running application
• provided by the Twisted Conch project
• Telnet and/or SSH

Bot Manhole
• SSH & Telnet access
• send message to any XMPP user
• grab bot statistics

xmppClientWithConsole.py

How to use?
• Live inspection rather than
trial & error debugging
• distributed apps - separate components
• any networking bridges, converters,
multi-purpose magic apps