Go-TCP

This project is a simple TCP-based chat application that allows multiple clients to connect to a server, register a username, and send messages. It supports both public messages (broadcast to all users) and private messages between two users.

Features

• User Registration: Clients register with a unique username.
• Public Messages: Clients can send public messages that are broadcast to all connected users.
• Private Messages: Clients can send private messages to specific users.
• Graceful Exit: Clients can gracefully disconnect from the server by sending an "EXIT" message.
• Error Handling: The server handles errors such as duplicate usernames, invalid message formats, and unknown users.

Requirements

• Go programming language (1.16+)

How to Run

1. Start the Server

To run the server, execute the following command:

go run server.go

The server will start on port 8080 and listen for incoming connections.

2. Run the Client

To run a client and connect to the server, execute the following command:

go run client.go <server_address>

Replace <server_address> with the IP address of the server.

For example, if the server is running locally:

go run client.go 127.0.0.1

3. Client Registration

After starting the client, you will be prompted to enter a username. The username must meet the following requirements:

• Must be unique (not already in use by another client).
• Must not exceed 20 characters.
• Must not contain spaces.

Once a valid username is provided, the server will confirm the registration.

4. Sending Messages

• Public Messages: To send a public message, simply type the message and press Enter. All connected users will receive the message.

• Private Messages: To send a private message to a specific user, use the following format:

  PMSG

  Replace <username> with the recipient's username and <message> with the content of the private message. Only the specified user will receive the message.

5. Exit

To gracefully disconnect from the server, type:

EXIT

The server will confirm the disconnection, and the client will exit.

Error Messages

The server will return the following error messages in case of invalid input:

• ERR 0: Username already taken.
• ERR 1: Username is too long (exceeds 20 characters).
• ERR 2: Username contains spaces.
• ERR 3: Unknown user when attempting to send a private message.
• ERR 4: Invalid message format.

Project Structure

• client.go: Handles the client-side functionality, including connecting to the server, user registration, sending and receiving messages.
• server.go: Manages the server-side functionality, including accepting client connections, handling user registrations, broadcasting messages, and managing private messages.

Example Usage

Public Message

John: Hello everyone!

Private Message

PMSG Jane How are you?

Exit

EXIT