ip

The ip module provides utilities for retrieving, comparing, validating, and converting IP addresses.

Basic Operations

• ip.address(): Returns your current IP address.
• ip.isEqual(addr1, addr2): Compares two IP addresses for equality.
• ip.isPrivate(addr): Checks if an IP address is private.
• ip.isV4Format(addr) / ip.isV6Format(addr): Validates the IP format.

Conversions and Bitwise Operations

• ip.toBuffer(addr): Converts an IP string to a Buffer.
• ip.toString(buffer): Converts a Buffer back to an IP string.
• ip.toLong(addr) / ip.fromLong(long): Converts between IPv4 strings and long integers.
• ip.mask(addr, mask): Returns the network address.
• ip.cidr(cidr): Returns the network address from a CIDR string.
• ip.not(mask): Returns the bitwise NOT of a mask.
• ip.or(addr, mask): Returns the bitwise OR of an address and a mask.

In-place Buffer Operations

You can operate on existing buffers using an offset to avoid extra allocations:

var buf = new Buffer(128);
var offset = 64;
ip.toBuffer('127.0.0.1', buf, offset);  // [127, 0, 0, 1] at offset 64
ip.toString(buf, offset, 4);            // '127.0.0.1'

var ip = require('ip');

ip.address() // my ip address
ip.isEqual('::1', '::0:1'); // true
ip.toBuffer('127.0.0.1') // Buffer([127, 0, 0, 1])
ip.toString(new Buffer([127, 0, 0, 1])) // 127.0.0.1
ip.fromPrefixLen(24) // 255.255.255.0
ip.mask('192.168.1.134', '255.255.255.0') // 192.168.1.0
ip.cidr('192.168.1.134/26') // 192.168.1.128
ip.not('255.255.255.0') // 0.0.0.255
ip.or('192.168.1.134', '0.0.0.255') // 192.168.1.255
ip.isPrivate('127.0.0.1') // true
ip.isV4Format('127.0.0.1'); // true
ip.isV6Format('::ffff:127.0.0.1'); // true

// operate on buffers in-place
var buf = new Buffer(128);
var offset = 64;
ip.toBuffer('127.0.0.1', buf, offset);  // [127, 0, 0, 1] at offset 64
ip.toString(buf, offset, 4);            // '127.0.0.1'

// ipv4 long conversion
ip.toLong('127.0.0.1'); // 2130706433
ip.fromLong(2130706433); // '127.0.0.1'

Use ip.subnet(address, mask) or ip.cidrSubnet(cidr) to retrieve detailed information about a network range. These methods return an object containing network details and a .contains(addr) method for range checking.

Subnet Object Structure

The returned object includes:

• networkAddress: The starting address of the network.
• firstAddress: The first usable address.
• lastAddress: The last usable address.
• broadcastAddress: The broadcast address.
• subnetMask: The subnet mask string.
• subnetMaskLength: The prefix length (e.g., 26).
• numHosts: Number of available hosts.
• length: Total length of the subnet.
• contains: A function to check if an address belongs to this subnet.

Usage Example

// Using CIDR notation
var subnet = ip.cidrSubnet('192.168.1.134/26');
console.log(subnet.networkAddress); // '192.168.1.128'

// Range checking
var isInRange = subnet.contains('192.168.1.190'); // true

ip.subnet('192.168.1.134', '255.255.255.192')
// { networkAddress: '192.168.1.128',
//   firstAddress: '192.168.1.129',
//   lastAddress: '192.168.1.190',
//   broadcastAddress: '192.168.1.191',
//   subnetMask: '255.255.255.192',
//   subnetMaskLength: 26,
//   numHosts: 62,
//   length: 64,
//   contains: function(addr){...} }

ip.cidrSubnet('192.168.1.134/26')
// Same as previous.

// range checking
ip.cidrSubnet('192.168.1.134/26').contains('192.168.1.190') // true