ComputerNetworks

Description

This project implements a simple TCP Echo Server and Client in C. The server listens for connections from clients and echoes back any messages it receives.

Files

• server.c: Source code for the TCP Echo Server
• client.c: Source code for the TCP Echo Client
• server: Compiled executable for the TCP Echo Server
• client: Compiled executable for the TCP Echo Client

Features

• TCP Echo Server: Listens on port 25020 and echoes back messages from clients
• TCP Echo Client: Connects to the server and sends a predefined greeting message
• Multi-client support: Server can handle multiple client connections sequentially
• Error handling: Both programs include comprehensive error checking

How to Use

Prerequisites

• GCC compiler
• Unix/Linux environment (for socket programming)

Compile (if needed)

To recompile the server and client from source:

gcc server.c -o server
gcc client.c -o client

Run the Server

Start the server first (it will listen on localhost:25020):

./server

The server will display:

TCP ECHO SERVER.
SERVER: Listening for clients... Press Ctrl + C to stop the server.

Run the Client

In a separate terminal, start the client:

./client

The client will:

1. Connect to the server
2. Send the message "===GOOD AFTERNOON==="
3. Receive and display the echoed message
4. Disconnect

Configuration

Both programs use the following default settings:

• IP Address: 127.0.0.1 (localhost)
• Port: 25020
• Buffer Size: 128 bytes

To modify these settings, edit the following variables in both server.c and client.c:

unsigned short serv_port = 25020;  // Change port number
char serv_ip[] = "127.0.0.1";       // Change IP address

Example Output

Server Output:

TCP ECHO SERVER.
SERVER: Listening for clients... Press Ctrl + C to stop the server.
SERVER: Connection from client 127.0.0.1 accepted.
SERVER: Echoed back ===GOOD AFTERNOON=== to 127.0.0.1.

Client Output:

TCP ECHO CLIENT
CLIENT: Connected to the server.
CLIENT: Message sent to echo server.
CLIENT: Message from the server: ===GOOD AFTERNOON===

Notes

• Ensure the server is running before starting the client
• The server handles one client at a time and closes the connection after echoing the message
• Press Ctrl + C to stop the server
• This implementation is designed for educational purposes and local testing

Author

Created as part of Computer Networks coursework.