Node.js Net Module

Here is a complete, beginner-friendly guide to the Node.js Net Module, explained with examples!

Node.js Net Module

The net module in Node.js allows you to create TCP servers and clients.
It is used for low-level networking operations—building chat servers, socket connections, proxies, IoT device communication, etc.

To use it:

1. Creating a TCP Server

A basic TCP server listens for client connections over a port.

Example: Simple TCP Server

const net = require("net");

const server = net.createServer((socket) => {
console.log("Client connected");

// Receive data from client
socket.on("data", (data) => {
console.log("Client says:", data.toString());
socket.write("Message received!");
});

// Client disconnect
socket.on("end", () => {
console.log("Client disconnected");
});
});

// Start server
server.listen(5000, () => {
console.log("TCP Server running on port 5000");
});

const net = require("net");

const server = net.createServer((socket) => {

console.log("Client connected");

// Receive data from client

socket.on("data", (data) => {

console.log("Client says:", data.toString());

socket.write("Message received!");

});

// Client disconnect

socket.on("end", () => {

console.log("Client disconnected");

});

// Start server

server.listen(5000, () => {

console.log("TCP Server running on port 5000");

});

Run server

2. Creating a TCP Client

A TCP client connects to a TCP server.

Example: Simple TCP Client

const net = require("net");

const client = net.createConnection(5000, "localhost", () => {
console.log("Connected to server");
client.write("Hello from client!");
});

// Receive response
client.on("data", (data) => {
console.log("Server says:", data.toString());
});

// On close
client.on("end", () => {
console.log("Disconnected from server");
});

const net = require("net");

const client = net.createConnection(5000, "localhost", () => {

console.log("Connected to server");

client.write("Hello from client!");

});

// Receive response

client.on("data", (data) => {

console.log("Server says:", data.toString());

});

// On close

client.on("end", () => {

console.log("Disconnected from server");

});

3. Important Socket Events

Event	Description
`data`	Fired when data is received
`end`	Client/server disconnects
`connect`	TCP connection established
`error`	Error occurs
`timeout`	Connection timeout

Example:

4. Writing Data to Socket

You can send strings, buffers, or JSON.

5. Using Encodings

6. Server Events

Event	Description
`connection`	Fired when a client connects
`error`	Server error
`close`	Server shuts down
`listening`	Server starts listening

Example:

7. Broadcasting Messages (Chat Server Example)

A TCP chat server where all connected clients receive message.

const net = require("net");

let clients = [];

const server = net.createServer((socket) => {
clients.push(socket);

socket.on("data", (msg) => {
clients.forEach((client) => {
if (client !== socket) {
client.write("User: " + msg);
}
});
});

socket.on("end", () => {
clients = clients.filter((c) => c !== socket);
});
});

server.listen(5000, () => {
console.log("Chat server running");
});

const net = require("net");

let clients = [];

const server = net.createServer((socket) => {

clients.push(socket);

socket.on("data", (msg) => {

clients.forEach((client) => {

if (client !== socket) {

client.write("User: " + msg);

}

});

socket.on("end", () => {

clients = clients.filter((c) => c !== socket);

});

server.listen(5000, () => {

console.log("Chat server running");

});

8. Checking Client Address Details

9. Half-Open Connections

Enable half-open TCP connections:

10. Closing Server

11. Use Cases of Net Module

✔ Real-time chat applications
✔ Custom TCP protocols
✔ Proxy servers
✔ Multiplayer game servers
✔ IoT device communication
✔ Inter-process communication

12. Difference Between Net and HTTP

Feature	`net` Module	`http` Module
Level	Low-level	High-level
Protocol	TCP	HTTP built over TCP
Use Case	Raw socket apps	Websites, APIs
Data	Binary or text	HTTP request/response

Node.js Net Module

Node.js Net Module

1. Creating a TCP Server

Example: Simple TCP Server

Run server

2. Creating a TCP Client

Example: Simple TCP Client

3. Important Socket Events

Example:

4. Writing Data to Socket

5. Using Encodings

6. Server Events

7. Broadcasting Messages (Chat Server Example)

8. Checking Client Address Details

9. Half-Open Connections

10. Closing Server

11. Use Cases of Net Module

12. Difference Between Net and HTTP

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Node.js Net Module

Node.js Net Module

1. Creating a TCP Server

Example: Simple TCP Server

Run server

2. Creating a TCP Client

Example: Simple TCP Client

3. Important Socket Events

Example:

4. Writing Data to Socket

5. Using Encodings

6. Server Events

7. Broadcasting Messages (Chat Server Example)

8. Checking Client Address Details

9. Half-Open Connections

10. Closing Server

11. Use Cases of Net Module

12. Difference Between Net and HTTP

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Node.js Perfomance & Scaling

Node.js Testing & Debugging