John Hofman's Design Study

My Project

This design study was introduced by my ENEL428 software assignment. The purpose of the assignment was to design a prototype of an Instant Messenger System using concurrent programming. The system was broken into two separate parts a client and a server. This design study is regarding the client program.

Design Study

The initial system uses a simple login model, a user attempts to log in with just a username which the server accepts or rejects.

Functional requirements of the client:

• Connect to a server.
• Login.
• Logout.
• Display the other users online.
• Start a conversation with another online user.
• Post Messages in a conversation.
• Invite other online users to a conversation.
• Leave a conversation.

Constraints:

• C++
• Uses POSIX threads for concurrency.

Room for Expansion:

• Other protocols, XMPP etc.
• Other GUI implementations, currently uses fltk-1.1.9

Initial Design

This is the design which is fully functional.

[UML]

Description

Concurrent Design: This design is an event driven system. There are two threads.

• The Inbox encapsulates a thread that reads and responds to packets from the server via the Socket.
• The GUI uses a thread to respond to user input and manipulate Chats and the UserManager.

Class Descriptions:

• Socket/ClientSocket: The Socket encapsulates a TCP Socket. It provides an interface to read/write packets to the socket.
• Inbox: Encapsulates a thread that reads packets from the ClientSocket, unpacks them and executes operations on the Chats and the UserManager.The Inbox also contains a map that links Chat objects to their ChatID's (This is nasty, why does the inbox have this map).
• Chat: Each chat represents a conversation with another user. The chat maintians a list of messagees

Other Stuff

Stuff that needs fixing:

• Chat map in Inbox
• Switch smell in Inbox to deal with packets? Polymorphism..? Which means that Socket will need a switch.

Simple chat Log