ChatWave

Overview

ChatWave is a terminal chat application written in C using socket programming. It supports two concurrency models — POSIX threads and the select() system call — for handling multiple clients simultaneously. Private messages, group chats, and file transfer are all supported. Messages and files are client-side encrypted before transmission, so nothing is readable on the wire. See the Features section for the full list.

Building

Requires GCC and pthreads (Linux / WSL recommended).

gcc -Wall -o serverThread serverThread.c -lpthread
gcc -Wall -o clientThread clientThread.c -lpthread
gcc -Wall -o server      server.c
gcc -Wall -o client      client.c -lpthread

Using Threads

serverThread.c and clientThread.c use a dedicated POSIX thread per client.

Start the server:

./serverThread <port>

Connect a client:

./clientThread <host> <port> <username>

Using Select

server.c and client.c use the select() system call to multiplex all connections in a single loop.

Start the server:

./server <port>

Connect a client:

./client <host> <port> <username>

A log file chat_logs/<username>.log is created for every client session. All received messages are written there after decryption.

Message Format

Action	Command
Private message	@username <message>
Send file	@username @file <filename>
Report a user	#username
Create group	$CREATE <groupname>
Join group	$JOIN <groupname>
Leave group	$LEAVE <groupname>
Send group message	$<groupname> <message>
List all clients	SHOW_ALL_CLIENTS
List all groups	SHOW_ALL_GROUPS
Disconnect	EXIT

Server admin commands (type in the server terminal)

Command	Effect
REMOVE <username>	Force-disconnect a client
DELETE <groupname>	Delete a group
CLOSE	Shut down the server

Features

• Handles up to 10 clients and 10 groups concurrently
• Unique username enforcement — duplicate connections are rejected
• Private messaging between any two connected clients
• Broadcast messaging to all active clients
• File transfer between clients (first line of file is transferred)
• Client-side encryption: messages are reversed and encoded as 3-digit ASCII before sending
• Client reporting system — clients kicked automatically when report threshold is reached
• Server-controlled client removal (REMOVE <username>)
• Configurable idle timeout (clients disconnected after inactivity)
• Group chat:
  • Create, join, and leave groups
  • Group messages delivered to all members except the sender
  • Empty groups are automatically cleaned up