Build Your First TCP Chat App Using Node.js 🚀💬

Are you prepared to explore the realm of real-time communication and networking? We'll use Node.js to create a straightforward yet effective TCP chat application in this step-by-step tutorial! 🌟

What is TCP? 🤔
One of the primary protocols in the Internet protocol suite is TCP (Transmission Control Protocol). It guarantees data transport between applications operating on hosts interacting via an IP network in a dependable, organised, and error-checked manner. Consider it your data's trustworthy postal service! 📮

Prerequisites 🛠️
Before we start, make sure you have:

• Node.js installed on your machine
• A code editor (VS Code recommended)
• Basic JavaScript knowledge
• Terminal/Command Prompt access

Step 1: Setting Up the Project 📁
First, let's create our project directory and initialize it:

mkdir tcp-chat-app
cd tcp-chat-app
npm init -y

That's it! We don't need any external dependencies since Node.js has built-in modules for TCP networking. 🎉

Step 2: Creating the TCP Server 🖥️
Create a file called server.js and let's build our chat server:

// server.js
const net = require('net');

// Array to store all connected clients
const clients = [];

// Create TCP server
const server = net.createServer((socket) => {
    console.log('✨ New client connected!');

    // Add new client to our list
    clients.push(socket);

    // Set encoding for received data
    socket.setEncoding('utf8');

    // Send welcome message to new client
    socket.write('🎉 Welcome to the TCP Chat Server!\n');
    socket.write('💬 Start typing to chat with others...\n\n');

    // Broadcast message to all clients when someone sends a message
    socket.on('data', (data) => {
        const message = data.toString().trim();
        if (message) {
            console.log(`📨 Message received: ${message}`);
            broadcast(`${socket.remoteAddress}: ${message}`, socket);
        }
    });

    // Handle client disconnection
    socket.on('end', () => {
        console.log('👋 Client disconnected');
        const index = clients.indexOf(socket);
        if (index !== -1) {
            clients.splice(index, 1);
        }
    });

    // Handle errors
    socket.on('error', (err) => {
        console.log('❌ Client error:', err.message);
    });
});

// Function to broadcast messages to all clients except the sender
function broadcast(message, sender) {
    clients.forEach((client) => {
        if (client !== sender && !client.destroyed) {
            client.write(`📢 ${message}\n`);
        }
    });
}

// Start the server
const PORT = 3000;
const HOST = 'localhost';

server.listen(PORT, HOST, () => {
    console.log(`🚀 TCP Chat Server running on ${HOST}:${PORT}`);
    console.log('⏳ Waiting for clients to connect...');
});

// Handle server errors
server.on('error', (err) => {
    console.log('❌ Server error:', err.message);
});

Step 3: Creating the TCP Client 📱
Now, create a file called client.js for our chat client:

// client.js
const net = require('net');
const readline = require('readline');

// Create interface for reading user input
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

// Create TCP client
const client = new net.Socket();

// Connect to server
const PORT = 3000;
const HOST = 'localhost';

client.connect(PORT, HOST, () => {
    console.log('✅ Connected to chat server!');
    console.log('💬 Type your messages and press Enter to send');
    console.log('⏹️  Type "exit" to quit\n');

    // Prompt for first message
    promptUser();
});

// Handle data received from server
client.on('data', (data) => {
    console.log(data.toString());
    promptUser();
});

// Handle connection close
client.on('close', () => {
    console.log('🔌 Connection closed');
    rl.close();
});

// Handle errors
client.on('error', (err) => {
    console.log('❌ Connection error:', err.message);
    rl.close();
});

// Function to prompt user for input
function promptUser() {
    rl.question('', (message) => {
        if (message.toLowerCase() === 'exit') {
            console.log('👋 Goodbye!');
            client.end();
            rl.close();
            return;
        }

        // Send message to server
        client.write(message);
    });
}

Step 4: Understanding the Code 🧠
Let's break down what we've built:

Server Breakdown:

• Server Creation 🏗️: We use net.createServer() to create a TCP server
• Client Management 👥: We store all connected clients in an array
• Message Broadcasting 📢: When a client sends a message, we forward it to all other clients
• Event Handling ⚡: We handle connection, data reception, disconnection, and errors

Client Breakdown:

• Connection Setup 🔌: The client connects to our server using net.Socket()
• User Input ⌨️: We use readline to get input from the user
• Message Display 📺: We show messages received from the server
• Graceful Exit 🚪: Users can type "exit" to quit the chat

Step 5: Running the Chat App 🏃‍♂️
Let's test our application! Open two terminal windows:

Terminal 1 (Server):

node server.js

Terminal 2 (Client 1):

node client.js

Terminal 3 (Client 2):

node client.js

Now you can send messages between clients! 🎊

Step 6: Testing the Application 🧪

• Start the server in one terminal
• Open multiple client terminals
• Send messages from different clients
• Watch the real-time magic happen! ✨

Common Issues and Solutions 🔧

• Port Already in Use ❌: Change the PORT number in both files
• Connection Refused 🔌: Make sure the server is running first
• Cannot Type Messages ⌨️: The readline interface might be blocked

Conclusion 🎉
Congratulations! 🥳 You've just built a functional TCP chat application using Node.js. You learned:

• ✅ How TCP networking works
• ✅ How to create TCP servers and clients
• ✅ Real-time message broadcasting
• ✅ Handling multiple client connections
• ✅ Basic networking concepts