BGCE ARCHIVE

# Simple UDP Server in Node.js

This is a **minimal UDP server** built using Node.js `dgram` module. It listens on `127.0.0.1:41234` and optionally replies back to the client.

## Files

- `server.js` : Contains the UDP server code.

## Requirements

- Node.js (v12+ recommended)
- npm

## How to Run

1. **Install dependencies (if any)**

This script uses only core Node.js modules, so no installation is required. But initialize your project for good practice:

```bash
npm init -y

2. Run the server

node server.js

You should see:

UDP Server listening on 127.0.0.1:41234

Code Explanation (Brief)

• dgram.createSocket("udp4") – creates an IPv4 UDP socket.
• server.on("message") – handles incoming datagrams.
• server.send() – sends a reply back to the client.
• server.bind() – binds the server to the specified port and host.

📡 Testing the Server

🔧 Using netcat (nc)

Open a separate terminal and run:

echo "Hello from client" | nc -u 127.0.0.1 41234

You should see the server log the received message and send a reply.

🔧 Using a Node.js UDP client

Create a simple client.js:

import dgram from "dgram";

const client = dgram.createSocket("udp4");
const msg = Buffer.from("Hello server!");

client.send(msg, 0, msg.length, 41234, "127.0.0.1", (err) => {
    if (err) console.error(err);
    else console.log("Message sent!");
    client.close();
});

Run it:

node client.js

Reference

• Node.js dgram documentation

Notes

• For production use, handle errors and edge cases gracefully.
• Use udp6 instead of udp4 for IPv6 sockets.
• Adjust HOST to 0.0.0.0 if you want to accept messages from any network interface.

Happy UDP hacking!