Network Chat Application

Systems Programming · TCP Client-Server Messaging
About

A TCP-based client-server chat application that enables real-time public and private messaging. Built entirely in C, the system relies on a custom binary protocol and utilizes I/O multiplexing to efficiently handle concurrent users and network communication without the overhead of multithreading or forking.

Key Highlights
—Designed and implemented a lightweight custom binary protocol using 16-bit headers for control messages and 32-bit headers for chat messages.
—Leveraged the select() system call for robust I/O multiplexing on both the client and server sides to monitor multiple sockets and standard input simultaneously.
—Implemented advanced data handling features, including message chunking for payloads over 2000 bytes, partial message buffering, and graceful disconnect management.
—Built a configurable GNU Make build system and utilized unit testing, GDB, and Valgrind to ensure memory safety and accurate header parsing.
Skills
CPOSIX SocketsTCPI/O MultiplexingGNU MakeGCCGDBValgrind
Images
Full chat session from Alice's perspective — showing username negotiation, public messaging, private messages with Bob, and user join/leave notifications as Charlie and Bob disconnect.

Full chat session from Alice's perspective — showing username negotiation, public messaging, private messages with Bob, and user join/leave notifications as Charlie and Bob disconnect.

Bob's view of the chat session — receiving public messages from all users, exchanging private messages with Alice, and handling an error when attempting to message a nonexistent user.

Bob's view of the chat session — receiving public messages from all users, exchanging private messages with Alice, and handling an error when attempting to message a nonexistent user.

Charlie's view demonstrating message visibility — public messages from all users are visible, while private messages between Alice and Bob are correctly excluded from Charlie's terminal.

Charlie's view demonstrating message visibility — public messages from all users are visible, while private messages between Alice and Bob are correctly excluded from Charlie's terminal.