IMDraw An Instant Message and Drawing Program Tim Poley Kelly Whitacre

Agenda Background IMDraw Design Decisions  Client/Server vs. Peer to Peer Model  TCP/IP vs. UDP  Design Diagram Programming Hurdles Future Work Demonstration Questions

Background Early Instant Messaging- Talk Big Players Today  AIM  MS Messenger  Jabber  Trillian Why IMDraw?

Design Decisions: Client/Server vs. Peer to Peer Model Client/Server  Advantages Server Manages Data Supports Off-line Messages  Disadvantages Single Point of Failure P2P  Advantages Performance Advantages with P2P Broadcasting File-Transfers  Disadvantages Lower Performance with Heavy Loads

Design Decisions: TCP/IP vs. UDP Message Protocol TCP  Advantages Connection Disruption Detection More Reliable (retransmits when necessary) Detects Congestion in the Network  Disadvantages Slower UDP  Advantages Fast, Simple Low Delay (no transmissions) End-to-End Encryption Near Real Time transmission  Disadvantages Possible out-of-order delivery of messages

Design Diagram

Programming Hurdles Updating User Interface Controls Across Threads  - C# delegates/events used Server Crash after Client Logs Off  - proper termination of threads used TCP Connection Terminates before it Sends Logout Message to Server

Future Work Secure Message Transfer UDP Message Protocol Multicasting User Defined Buddy Lists Add Additional Capabilities to Drawing Tool Streamline Messages

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Questions?

Demonstration

IMDraw Message Protocol- Supplemental IMDraw| | | | | | |.... Command: Login(0), Logout(3), Message(1), ClientList(2)

TCP-Supplemental