Nodejs: how to get local IP address in node

Node.js: How to Get Local IP Address

In Node.js, you can easily retrieve the local IP address of your machine by utilizing the os module. This module provides a variety of operating system-related utility functions, including information about network interfaces.

Here’s a function that will return the first non-internal IPv4 address found on any of your network interfaces:

function getLocalIPAddress() {
    const os = require('os');
    const interfaces = os.networkInterfaces();

    for (const devName in interfaces) {
        const iface = interfaces[devName];

        for (const alias of iface) {
            if (alias.family === 'IPv4' && alias.address !== '127.0.0.1' && !alias.internal) {
                return alias.address;
            }
        }
    }

    // If no valid IP address is found, return null or an error message.
    return null;
}

// Example usage:
const ipAddress = getLocalIPAddress();
console.log(`Local IP Address: ${ipAddress}`);

Explanation

1. Importing the os Module:

   • The os module is required at the beginning of the script using require('os'). This module provides basic operating system-related information and utilities.

2. Accessing Network Interfaces:

   • The os.networkInterfaces() method returns an object containing the network interfaces of the machine. Each key in this object represents a network interface name, and the value is an array of objects representing each interface configuration.

3. Iterating Through Interfaces:

   • We loop through each network interface using a for...in loop.
   • For each interface, we iterate through its configuration objects using another loop.

4. Filtering Valid IP Addresses:

   • Inside the inner loop, we check if the current configuration (alias) is an IPv4 address (alias.family === 'IPv4'), not the loopback address (alias.address !== '127.0.0.1'), and not an internal address (!alias.internal).
   • If all conditions are met, we return the IP address.

5. Returning Default Value:

   • If no valid IP address is found after iterating through all interfaces, the function returns null.

Usage Example

To use the function, simply call it and log the result:

const ipAddress = getLocalIPAddress();
if (ipAddress) {
    console.log(`Local IP Address: ${ipAddress}`);
} else {
    console.log("No valid IP address found.");
}

This function should work well for most cases where you need to find the local IP address of the machine running your Node.js application.