1. ShortTalk - http://shorttalk.sourceforge.net/
XMPP messaging in a peer to peer manner
Instructed by:
Edward Bortnikov
Supervisor:
Dr. Ilana David
Developed by:
Michael Gartsbein

2. Project goal
Create a package that uses the XMPP protocol as the transport but distributes the server functionality among the participating nodes
Create a lightweight XMPP server than can be embedded to each node in system
Develop a demo messaging application

3. Motivation To have fun Explore the filed of distributed systems
Experience with the newest open source development tools
Experience …
Experience is what one gets when he doesn’t get what he wanted

4. Constraints OS independence Use only open source modules
The whole system should be small and understandable by a single person
The whole system should be delivered as a homogenous python package

5. Why distribute? Distributed p2p: Client server:
Many same or almost same nodes
New participating nodes can contribute resources
Harder to make secure
Can be very scalable
Can be very fault tolerant
Client server:
There are client nodes and one or (a much smaller) set of servers
There are limitations on scalability
New users consume resources from servers
Easier to monitor/control access

6. Example of distributed system
File sharing (torrents)‏
Distributed hash tables
Distributed file system
Messaging (skype)‏
ki/List_of_distributed_co mputing_projects

7. Peer to peer Natural to use p2p in distributed systems
Bandwidth and other resources sharing
Symmetric design
Scalable
Many DS are p2p

8. What is XMPP? Xml based messaging protocol also known as jabber
Open protocol and internet standard
Used by google in google-talk and in many other messaging systems *

9. XMPP (cont. 1) XMPP uses a servers based scheme to deliver messages.
Sender’s server delivers the message to the recipient’s server, and the last to the recipient

10. Why python? Developing with python is fun!
A free and 100% open source platform
OS independent and extra flexible language
linux+unix/mac/win32/winCE+mobile
Millions of packages
If its good for google, NASA and nokia– it should be good enough for me

11. Why python? (cont.)‏ Experiencing with new programming paradigm
Learning new language and new set of tools

12. Architecture
Use an open dht system (bamboo open-dht) for the signaling
Use the xmpp protocol at the transport between nodes
The dht application will use a small dht-handler, xmpp client and server to communicate

13. Block scheme DHT node ShortTalk application instance GUI XMPP server
XMPP client
DHT handler
User agent
ShortTalk application instance
GUI
XMPP server
XMPP client
DHT handler
User agent
P2p session

14. The technology
The project is built as a composition of python packages
XMPP – client and server according to the XMPP standard RFC 3920
DHT – free publicly open DHT service – based on the bamboo project
Tkinter – a “standard” python GUI

15. Main technical milestones
Creating a smart and reliable DHT handler
Assembling a lightweight XMPP sever engine that will run on both linux and windows
Most of the existing available XMPP servers are pretty heavy and complicated, and contain features I don't need.

16. Main technical milestones (cont 1)
Embedding XMPP client to the project
Assembling the whole system together in a demo messaging application
Must do GUI 

17. Entities

18. Typical workflow sequence

19. Step by step workflow Start the application
Creating the DHT handler and choosing a closet DHT node to work with
When a the connection breaks, a new one is transparently established
XMPP client
DHT handler
User agent

20. Step by step workflow (cont 1)
ShortTalk application instance
Starting the XMPP server
Starting the XMPP client and logging to the server
Callbacks to GUI are set
User agent
DHT handler
XMPP client
XMPP server
GUI

21. Step by step workflow (cont 2)
Subscribing
User can subscribe to DHT handler for event -> other users go online

22. Step by step workflow (cont 3)
ShortTalk application instance
Logging to the DHT
This will create an entry in the DHT with name-ip and will refresh it
The user agent will get notifications on when users will get online
User agent
DHT handler
XMPP client
XMPP server
GUI

23. Step by step workflow (cont 4)
GUI
XMPP server
XMPP client
DHT handler
User agent 1 2
Chatting
User can send a message to another online user
The message will go from user’s XMPP client directly to remote user XMPP server 3

24. Look and feel

25. Special thanks
To Eddie Bortnikov for the whole project concept and support
To the lab for the infrastructure
XMPP community and specially Alexey "Snake" Nezhdanov for python’s XMPP support
Open bamboo team for the free DHT
To sourceforge for hosting and technological support
To Guido van Rossum for the language

26. Future development ??? Embedding the DHT with the application
Adding authentication
Changing the polling of the DHT to a event driven pub/sub
Using DHT to implement “offline messaging” and saving user list in the grid
Through NAT support
???

27. Future Development (cont.)
Contact information
Project developer’s page

28. News from the world XEP-0174: Serverless Messaging Python 3.0
A new standard from October
Python 3.0
A new significant release in December 2008

29. This slide was left blank on purpose