Net

[Stable: 2 - Stable]

Source Code: lib/net.js

The node:net module provides an asynchronous network API for creating stream-based TCP or IPC servers (net.createServer()) and clients (net.createConnection()).

It can be accessed using:

ESMCJS

import net from 'node:net';

const net = require('node:net');

IPC support

[History]

Version	Changes
v20.8.0	Support binding to abstract Unix domain socket path like `\0abstract`. We can bind '\0' for Node.js `\< v20.4.0`.

The node:net module supports IPC with named pipes on Windows, and Unix domain sockets on other operating systems.

Identifying paths for IPC connections

net.connect(), net.createConnection(), server.listen(), and socket.connect() take a path parameter to identify IPC endpoints.

On Unix, the local domain is also known as the Unix domain. The path is a file system pathname. It will throw an error when the length of pathname is greater than the length of sizeof(sockaddr_un.sun_path). Typical values are 107 bytes on Linux and 103 bytes on macOS. If a Node.js API abstraction creates the Unix domain socket, it will unlink the Unix domain socket as well. For example, net.createServer() may create a Unix domain socket and server.close() will unlink it. But if a user creates the Unix domain socket outside of these abstractions, the user will need to remove it. The same applies when a Node.js API creates a Unix domain socket but the program then crashes. In short, a Unix domain socket will be visible in the file system and will persist until unlinked. On Linux, You can use Unix abstract socket by adding \0 to the beginning of the path, such as \0abstract. The path to the Unix abstract socket is not visible in the file system and it will disappear automatically when all open references to the socket are closed.

On Windows, the local domain is implemented using a named pipe. The path must refer to an entry in \\?\pipe\ or \\.\pipe\. Any characters are permitted, but the latter may do some processing of pipe names, such as resolving .. sequences. Despite how it might look, the pipe namespace is flat. Pipes will not persist. They are removed when the last reference to them is closed. Unlike Unix domain sockets, Windows will close and remove the pipe when the owning process exits.

JavaScript string escaping requires paths to be specified with extra backslash escaping such as:

net.createServer().listen(
  path.join('\\\\?\\pipe', process.cwd(), 'myctl'));

Class: `net.BlockList`

Added in: v15.0.0, v14.18.0

The BlockList object can be used with some network APIs to specify rules for disabling inbound or outbound access to specific IP addresses, IP ranges, or IP subnets.

`blockList.addAddress(address[, type])`

Added in: v15.0.0, v14.18.0

address <string> | <net.SocketAddress> An IPv4 or IPv6 address.
type <string> Either 'ipv4' or 'ipv6'. Default: 'ipv4'.

Adds a rule to block the given IP address.

`blockList.addRange(start, end[, type])`

Added in: v15.0.0, v14.18.0

start <string> | <net.SocketAddress> The starting IPv4 or IPv6 address in the range.
end <string> | <net.SocketAddress> The ending IPv4 or IPv6 address in the range.
type <string> Either 'ipv4' or 'ipv6'. Default: 'ipv4'.

Adds a rule to block a range of IP addresses from start (inclusive) to end (inclusive).

`blockList.addSubnet(net, prefix[, type])`

Added in: v15.0.0, v14.18.0

net <string> | <net.SocketAddress> The network IPv4 or IPv6 address.
prefix <number> The number of CIDR prefix bits. For IPv4, this must be a value between 0 and 32. For IPv6, this must be between 0 and 128.
type <string> Either 'ipv4' or 'ipv6'. Default: 'ipv4'.

Adds a rule to block a range of IP addresses specified as a subnet mask.

`blockList.check(address[, type])`

Added in: v15.0.0, v14.18.0

address <string> | <net.SocketAddress> The IP address to check
type <string> Either 'ipv4' or 'ipv6'. Default: 'ipv4'.
Returns: <boolean>

Returns true if the given IP address matches any of the rules added to the BlockList.

const blockList = new net.BlockList();
blockList.addAddress('123.123.123.123');
blockList.addRange('10.0.0.1', '10.0.0.10');
blockList.addSubnet('8592:757c:efae:4e45::', 64, 'ipv6');

console.log(blockList.check('123.123.123.123'));  // Prints: true
console.log(blockList.check('10.0.0.3'));  // Prints: true
console.log(blockList.check('222.111.111.222'));  // Prints: false

// IPv6 notation for IPv4 addresses works:
console.log(blockList.check('::ffff:7b7b:7b7b', 'ipv6')); // Prints: true
console.log(blockList.check('::ffff:123.123.123.123', 'ipv6')); // Prints: true

`blockList.rules`

Added in: v15.0.0, v14.18.0

Type: <string[]>

The list of rules added to the blocklist.