CS330: Programming Assignment: Chat Application using C Sockets

Background

In the digital age, chat applications are essential for real-time communication, whether for personal conversations, professional collaboration, or social networking. These applications often rely on client-server architectures where the server handles incoming messages from multiple clients, and the clients send and receive messages from one another.

In this assignment, you will gain hands-on experience with socket programming, multi-threading, and basic client-server design. By implementing a chat application in C, you will deepen your understanding of how communication between computers works over a network.

Objective

The objective of this assignment is to implement a basic chat application that uses C sockets to enable client-server communication. Specifically, you will:

1. Create a server that listens for incoming client connections.
2. Develop a client application that connects to the server to send and receive messages.
3. Explore multi-threading by ensuring that the server can handle multiple clients simultaneously.
4. Learn how messages are passed over TCP/IP using sockets.

Server Implementation

1. Socket Creation and Binding

• Create a TCP socket in the server.
• Bind the socket to a specified port (e.g., 9090).
• Make sure the server listens for incoming connections.

2. Handling Multiple Clients

• Use multi-threading (e.g., pthreads) or I/O multiplexing (e.g., select()) to handle multiple clients at once.
• Each client connection should be handled by a separate thread or using non-blocking I/O, ensuring the server can continue to accept new clients while handling active ones.

3. Message Handling

• The server should receive messages from clients and broadcast these messages to all connected clients.
• Print all received messages to the server console for debugging purposes.

4. Graceful Client Termination

• Implement signal handling (e.g., Ctrl+C) for graceful shutdown of the server.
• Ensure that the server properly cleans up and closes any open sockets when shutting down.

Client Implementation

1. Socket Creation

• Implement a client that creates a socket and connects to the server.

2. User Input

• The client should continuously accept user input from the console.

3. Message Sending

• Allow the client to send messages to the server when the user types a message and presses “Enter”.

4. Receiving Messages

• The client should listen for incoming messages from the server and display them in the client console.

5. Exit Command (Extra Credit)

• Implement an “Exit” or “Escape” command that allows the user to gracefully leave the chat, disconnecting from the server.

Technical Specifications

• Programming Language: C
• Sockets: TCP sockets using the socket(), bind(), listen(), accept(), recv(), and send() functions.
• Concurrency: Use the select() system call for non-blocking I/O or pthreads for handling multiple client connections.
• Compilation: Provide detailed instructions on how to compile the server and client code using gcc (e.g., gcc -o server tcp_server.c -lpthread).

Simple Testing Procedure

1. Start the Server:
   • Compile and run the server using the provided instructions.
   • The server should output a message indicating that it is listening for connections, such as:

     Server is listening on port 9090...
     

2. Start Multiple Clients:
   • Compile and run the client code in different terminal windows.
   • Each client should connect to the server and be able to send messages.
   • Messages sent from one client should be echoed back and visible on all connected clients’ terminals.
3. Testing Multiple Clients:
   • Test with at least three clients to ensure the server is properly broadcasting messages to all connected clients.

Grading Criteria

Functionality (60%)

• Server:
  • Correctly accepts and handles multiple client connections concurrently.
  • Broadcasts messages to all connected clients.
  • Gracefully handles client disconnections and server shutdown.
• Client:
  • Correctly sends and receives messages.
  • Handles user input and displays messages correctly.

Code Quality (20%)

• Clear, organized code with appropriate variable names and structure.
• Proper error handling for socket operations.
• Use of comments and documentation to explain key parts of the code.

Documentation (20%)

• A README file that includes:
  • A brief description of the application and its functionality.
  • Clear, step-by-step instructions on how to compile and run the server and client.
  • Example usage of the program with expected behavior.

Code Snippets

• tcp_client.c: Client-side code for sending and receiving messages.
• tcp_server.c: Server-side code for handling multiple clients and broadcasting messages.
• Synchronous I/O Multiplexing using select: Information on how to use select() for non-blocking I/O multiplexing.

Grading Submission

• Submit your completed code, along with the README and any other relevant files, to Marmoset by the due date specified in the course syllabus.
• Include a brief report summarizing your implementation, challenges faced, and solutions.

Suggested Improvements/Extensions:

• Extra Credit:
  • Add a feature that timestamps messages.
  • Implement a private messaging system where users can message each other individually.
  • Include a “list users” command to show all connected clients.