echo_server.js

// echo_server.js

const net = require('net');

// Define the port for the echo server to listen on
const PORT = 12345;

// Create a TCP server
const server = net.createServer((socket) => {
    // 'connection' event fires when a new client connects
    console.log(`Client connected from: ${socket.remoteAddress}:${socket.remotePort}`);

    // 'data' event fires when data is received from the client
    socket.on('data', (data) => {
        const receivedMessage = data.toString().trim(); // Convert Buffer to string and trim whitespace
        console.log(`Server: Received "${receivedMessage}" from ${socket.remoteAddress}:${socket.remotePort}`);

        // Echo the received data back to the client
        socket.write(`Echo from Server: "${receivedMessage}"\n`);
    });

    // 'end' event fires when the client disconnects
    socket.on('end', () => {
        console.log(`Client disconnected: ${socket.remoteAddress}:${socket.remotePort}`);
    });

    // 'error' event fires if there's a socket error
    socket.on('error', (err) => {
        console.error(`Socket error for ${socket.remoteAddress}:${socket.remotePort}: ${err.message}`);
    });
});

// Listen for connections on the specified port
server.listen(PORT, () => {
    console.log(`Server: Listening on port ${PORT}`);
    console.log(`To connect, use: nc 127.0.0.1 ${PORT}`);
});

// Handle server errors (e.g., port already in use)
server.on('error', (err) => {
    if (err.code === 'EADDRINUSE') {
        console.error(`Error: Port ${PORT} is already in use. Please choose another port or close the application using it.`);
    } else {
        console.error(`Server error: ${err.message}`);
    }
});