C Multi-Client Chat Server

A multi-threaded TCP sockets chat server that supports multiple concurrent clients.

Overview

This project implements a client-server architecture with the following features:

• Multi-threaded design: Both client and server use separate threads for handling message sending, receiving, and processing
• Non-blocking I/O: Socket operations are non-blocking for better performance
• Message queue mechanism: Uses a thread-safe message queue for handling incoming messages
• Connection management: Handles multiple client connections simultaneously using TCP sockets.

Components

Server

The server component receives connections from multiple clients, processes their messages, and broadcasts them to all connected clients. Key features:

• Accepts and manages multiple client connections
• Thread-safe client list management
• Processes and broadcasts messages
• Coordinates shutdown when all clients have finished sending messages

Client

The client component is a fuzzer (mainly for testing the server) which connects to the server, sends a specified number of random messages, and receives messages from all clients.

Key features:

• Simultaneous message sending and receiving using threads
• Logs received messages to a specified file
• Generates random content for test messages
• Terminates gracefully after sending specified number of messages

Message Protocol

Messages have a simple format:

1. Type byte: 0 for regular messages, 1 for termination signals
2. Sender information: For type 0 messages, contains sender IP and port
3. Message content: The actual message data
4. Terminator: Newline character (\n)

Usage

Server

./server <port number> <# of clients>

Parameters:

• port number: The port on which the server will listen for connections
• # of clients: The number of expected client connections

Client

./client <IP address> <port number> <# of messages> <log file path>

Parameters:

• IP address: IP address of the server
• port number: Port number the server is listening on
• # of messages: Number of messages to send before terminating
• log file path: Path to file where received messages will be logged

Build Instructions

Compile the project using the following commands:

# Compile server
gcc -o server server.c -pthread

# Compile client
gcc -o client client.c -pthread

Example Session

1. Start the server (on port 8080, expecting 3 clients): ./server 8080 3

2. Start 3 clients (each sending 10,15,20 messages, writing received messages to their own log files) :

./client 127.0.0.1 8080 10 client1.log
./client 127.0.0.1 8080 15 client2.log
./client 127.0.0.1 8080 20 client3.log

4. Each client will send its specified number of messages, then signal completion by sending a termination message
5. When all clients have signaled completion, the server will send termination messages to all clients
6. All processes will exit gracefully

Technical Implementation

• Written in C using POSIX threads and socket APIs
• Uses TCP sockets for reliable, ordered message delivery
• Uses mutex locks and condition variables for thread synchronization
• Implements efficient buffer management for message processing
• Uses non-blocking I/O for better performance and responsiveness

Testing

Criterion is used for unit tests. Server's basic features are tested (setting socket to non-blocking, adding clients, enqueueing messages, message handling, etc)