FM / api

/usr/share/doc/nodejs/api

Name	Size	Mode	Actions
assets/	-	0755	rm
addons.html	85172	0644	edit dl rm
addons.json.gz	11188	0644	edit dl rm
addons.md	41013	0644	edit dl rm
all.html	4598048	0644	edit dl rm
all.json.gz	681643	0644	edit dl rm
assert.html	110665	0644	edit dl rm
assert.json.gz	12007	0644	edit dl rm
assert.md	47147	0644	edit dl rm
async_hooks.html	83599	0644	edit dl rm
async_hooks.json.gz	14085	0644	edit dl rm
async_hooks.md	38888	0644	edit dl rm
buffer.html	245762	0644	edit dl rm
buffer.json.gz	24105	0644	edit dl rm
buffer.md	105044	0644	edit dl rm
child_process.html	136767	0644	edit dl rm
child_process.json.gz	19399	0644	edit dl rm
child_process.md	62919	0644	edit dl rm
cli.html	87936	0644	edit dl rm
cli.json.gz	16615	0644	edit dl rm
cli.md	42263	0644	edit dl rm
cluster.html	60116	0644	edit dl rm
cluster.json.gz	9557	0644	edit dl rm
cluster.md	25426	0644	edit dl rm
console.html	46093	0644	edit dl rm
console.json.gz	6056	0644	edit dl rm
console.md	16431	0644	edit dl rm
crypto.html	283043	0644	edit dl rm
crypto.json.gz	32118	0644	edit dl rm
crypto.md	125198	0644	edit dl rm
debugger.html	18089	0644	edit dl rm
debugger.json.gz	2820	0644	edit dl rm
debugger.md	6133	0644	edit dl rm
deprecations.html	138537	0644	edit dl rm
deprecations.json.gz	18470	0644	edit dl rm
deprecations.md	79120	0644	edit dl rm
dgram.html	62425	0644	edit dl rm
dgram.json.gz	9630	0644	edit dl rm
dgram.md	27746	0644	edit dl rm
dns.html	98289	0644	edit dl rm
dns.json.gz	13838	0644	edit dl rm
dns.md	40799	0644	edit dl rm
documentation.html	10978	0644	edit dl rm
documentation.json	3328	0644	edit dl rm
documentation.md	2247	0644	edit dl rm
domain.html	36301	0644	edit dl rm
domain.json.gz	6355	0644	edit dl rm
domain.md	15521	0644	edit dl rm
embedding.html	18165	0644	edit dl rm
embedding.json.gz	3625	0644	edit dl rm
embedding.md	8811	0644	edit dl rm
errors.html	182982	0644	edit dl rm
errors.json.gz	36479	0644	edit dl rm
errors.md	81734	0644	edit dl rm
esm.html	92490	0644	edit dl rm
esm.json.gz	15054	0644	edit dl rm
esm.md	48466	0644	edit dl rm
events.html	75986	0644	edit dl rm
events.json.gz	9561	0644	edit dl rm
events.md	28823	0644	edit dl rm
fs.html	437179	0644	edit dl rm
fs.json.gz	47095	0644	edit dl rm
fs.md	187735	0644	edit dl rm
globals.html	19795	0644	edit dl rm
globals.json.gz	2525	0644	edit dl rm
globals.md	5838	0644	edit dl rm
http.html	164378	0644	edit dl rm
http.json.gz	25888	0644	edit dl rm
http.md	74465	0644	edit dl rm
http2.html	256451	0644	edit dl rm
http2.json.gz	37157	0644	edit dl rm
http2.md	121722	0644	edit dl rm
https.html	38345	0644	edit dl rm
https.json.gz	4847	0644	edit dl rm
https.md	13942	0644	edit dl rm
index.html	10087	0644	edit dl rm
index.json	54	0644	edit dl rm
index.md	1825	0644	edit dl rm
inspector.html	22433	0644	edit dl rm
inspector.json.gz	3338	0644	edit dl rm
inspector.md	6825	0644	edit dl rm
intl.html	23154	0644	edit dl rm
intl.json.gz	4038	0644	edit dl rm
intl.md	11092	0644	edit dl rm
module.html	21739	0644	edit dl rm
module.json.gz	2821	0644	edit dl rm
module.md	5341	0644	edit dl rm
modules.html	61333	0644	edit dl rm
modules.json.gz	11897	0644	edit dl rm
modules.md	30610	0644	edit dl rm
n-api.html	340382	0644	edit dl rm
n-api.json.gz	48682	0644	edit dl rm
n-api.md	206268	0644	edit dl rm
net.html	95113	0644	edit dl rm
net.json.gz	14265	0644	edit dl rm
net.md	40473	0644	edit dl rm
os.html	58658	0644	edit dl rm
os.json.gz	8576	0644	edit dl rm
os.md	34632	0644	edit dl rm
packages.html	65483	0644	edit dl rm
packages.json.gz	12401	0644	edit dl rm
packages.md	36538	0644	edit dl rm
path.html	39321	0644	edit dl rm
path.json.gz	4873	0644	edit dl rm
path.md	14750	0644	edit dl rm
perf_hooks.html	56215	0644	edit dl rm
perf_hooks.json.gz	6973	0644	edit dl rm
perf_hooks.md	20116	0644	edit dl rm
policy.html	15908	0644	edit dl rm
policy.json.gz	2908	0644	edit dl rm
policy.md	6324	0644	edit dl rm
process.html	169341	0644	edit dl rm
process.json.gz	27734	0644	edit dl rm
process.md	82162	0644	edit dl rm
punycode.html	16904	0644	edit dl rm
punycode.json.gz	1939	0644	edit dl rm
punycode.md	4063	0644	edit dl rm
querystring.html	19334	0644	edit dl rm
querystring.json.gz	2519	0644	edit dl rm
querystring.md	5423	0644	edit dl rm
readline.html	58434	0644	edit dl rm
readline.json.gz	8835	0644	edit dl rm
readline.md	25133	0644	edit dl rm
repl.html	54152	0644	edit dl rm
repl.json.gz	10053	0644	edit dl rm
repl.md	23754	0644	edit dl rm
report.html	44941	0644	edit dl rm
report.json.gz	6227	0644	edit dl rm
report.md	18287	0644	edit dl rm
stream.html	200501	0644	edit dl rm
stream.json.gz	34485	0644	edit dl rm
stream.md	98619	0644	edit dl rm
string_decoder.html	14415	0644	edit dl rm
string_decoder.json.gz	1545	0644	edit dl rm
string_decoder.md	2934	0644	edit dl rm
synopsis.html	11475	0644	edit dl rm
synopsis.json	3013	0644	edit dl rm
synopsis.md	2129	0644	edit dl rm
timers.html	27467	0644	edit dl rm
timers.json.gz	3637	0644	edit dl rm
timers.md	9738	0644	edit dl rm
tls.html	148381	0644	edit dl rm
tls.json.gz	29988	0644	edit dl rm
tls.md	81388	0644	edit dl rm
tracing.html	19586	0644	edit dl rm
tracing.json.gz	2829	0644	edit dl rm
tracing.md	6756	0644	edit dl rm
tty.html	26930	0644	edit dl rm
tty.json.gz	3758	0644	edit dl rm
tty.md	8989	0644	edit dl rm
url.html	97495	0644	edit dl rm
url.json.gz	13611	0644	edit dl rm
url.md	44869	0644	edit dl rm
util.html	178081	0644	edit dl rm
util.json.gz	20542	0644	edit dl rm
util.md	71255	0644	edit dl rm
v8.html	44688	0644	edit dl rm
v8.json.gz	6082	0644	edit dl rm
v8.md	15533	0644	edit dl rm
vm.html	103392	0644	edit dl rm
vm.json.gz	14023	0644	edit dl rm
vm.md	48293	0644	edit dl rm
wasi.html	17088	0644	edit dl rm
wasi.json.gz	2814	0644	edit dl rm
wasi.md	5932	0644	edit dl rm
worker_threads.html	70808	0644	edit dl rm
worker_threads.json.gz	11326	0644	edit dl rm
worker_threads.md	33883	0644	edit dl rm
zlib.html	90124	0644	edit dl rm
zlib.json.gz	10569	0644	edit dl rm
zlib.md	35697	0644	edit dl rm

Edit: /usr/share/doc/nodejs/api/net.md (40473B)

# Net

> Stability: 2 - Stable

The `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:

```js
const net = require('net');
```

## IPC support

The `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
filesystem pathname. It gets truncated to an OS-dependent length of
`sizeof(sockaddr_un.sun_path) - 1`. 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 filesystem and
will persist until unlinked.

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:

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

## Class: `net.Server`

* Extends: {EventEmitter}

This class is used to create a TCP or [IPC][] server.

### `new net.Server([options][, connectionListener])`

* `options` {Object} See
  [`net.createServer([options][, connectionListener])`][`net.createServer()`].
* `connectionListener` {Function} Automatically set as a listener for the
  [`'connection'`][] event.
* Returns: {net.Server}

`net.Server` is an [`EventEmitter`][] with the following events:

### Event: `'close'`

Emitted when the server closes. If connections exist, this
event is not emitted until all connections are ended.

### Event: `'connection'`

* {net.Socket} The connection object

Emitted when a new connection is made. `socket` is an instance of
`net.Socket`.

### Event: `'error'`

* {Error}

Emitted when an error occurs. Unlike [`net.Socket`][], the [`'close'`][]
event will **not** be emitted directly following this event unless
[`server.close()`][] is manually called. See the example in discussion of
[`server.listen()`][].

### Event: `'listening'`

Emitted when the server has been bound after calling [`server.listen()`][].

### `server.address()`

* Returns: {Object|string|null}

Returns the bound `address`, the address `family` name, and `port` of the server
as reported by the operating system if listening on an IP socket
(useful to find which port was assigned when getting an OS-assigned address):
`{ port: 12346, family: 'IPv4', address: '127.0.0.1' }`.

For a server listening on a pipe or Unix domain socket, the name is returned
as a string.

```js
const server = net.createServer((socket) => {
  socket.end('goodbye\n');
}).on('error', (err) => {
  // Handle errors here.
  throw err;
});

// Grab an arbitrary unused port.
server.listen(() => {
  console.log('opened server on', server.address());
});
```

`server.address()` returns `null` before the `'listening'` event has been
emitted or after calling `server.close()`.

### `server.close([callback])`

* `callback` {Function} Called when the server is closed.
* Returns: {net.Server}

Stops the server from accepting new connections and keeps existing
connections. This function is asynchronous, the server is finally closed
when all connections are ended and the server emits a [`'close'`][] event.
The optional `callback` will be called once the `'close'` event occurs. Unlike
that event, it will be called with an `Error` as its only argument if the server
was not open when it was closed.

### `server.connections`

> Stability: 0 - Deprecated: Use [`server.getConnections()`][] instead.

* {integer|null}

The number of concurrent connections on the server.

This becomes `null` when sending a socket to a child with
[`child_process.fork()`][]. To poll forks and get current number of active
connections, use asynchronous [`server.getConnections()`][] instead.

### `server.getConnections(callback)`

* `callback` {Function}
* Returns: {net.Server}

Asynchronously get the number of concurrent connections on the server. Works
when sockets were sent to forks.

Callback should take two arguments `err` and `count`.

### `server.listen()`

Start a server listening for connections. A `net.Server` can be a TCP or
an [IPC][] server depending on what it listens to.

Possible signatures:

* [`server.listen(handle[, backlog][, callback])`][`server.listen(handle)`]
* [`server.listen(options[, callback])`][`server.listen(options)`]
* [`server.listen(path[, backlog][, callback])`][`server.listen(path)`]
  for [IPC][] servers
* <a href="#net_server_listen_port_host_backlog_callback">
  <code>server.listen([port[, host[, backlog]]][, callback])</code></a>
  for TCP servers

This function is asynchronous. When the server starts listening, the
[`'listening'`][] event will be emitted. The last parameter `callback`
will be added as a listener for the [`'listening'`][] event.

All `listen()` methods can take a `backlog` parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as `tcp_max_syn_backlog` and `somaxconn`
on Linux. The default value of this parameter is 511 (not 512).

All [`net.Socket`][] are set to `SO_REUSEADDR` (see [`socket(7)`][] for
details).

The `server.listen()` method can be called again if and only if there was an
error during the first `server.listen()` call or `server.close()` has been
called. Otherwise, an `ERR_SERVER_ALREADY_LISTEN` error will be thrown.

One of the most common errors raised when listening is `EADDRINUSE`.
This happens when another server is already listening on the requested
`port`/`path`/`handle`. One way to handle this would be to retry
after a certain amount of time:

```js
server.on('error', (e) => {
  if (e.code === 'EADDRINUSE') {
    console.log('Address in use, retrying...');
    setTimeout(() => {
      server.close();
      server.listen(PORT, HOST);
    }, 1000);
  }
});
```

#### `server.listen(handle[, backlog][, callback])`

* `handle` {Object}
* `backlog` {number} Common parameter of [`server.listen()`][] functions
* `callback` {Function}
* Returns: {net.Server}

Start a server listening for connections on a given `handle` that has
already been bound to a port, a Unix domain socket, or a Windows named pipe.

The `handle` object can be either a server, a socket (anything with an
underlying `_handle` member), or an object with an `fd` member that is a
valid file descriptor.

Listening on a file descriptor is not supported on Windows.

#### `server.listen(options[, callback])`

* `options` {Object} Required. Supports the following properties:
  * `port` {number}
  * `host` {string}
  * `path` {string} Will be ignored if `port` is specified. See
    [Identifying paths for IPC connections][].
  * `backlog` {number} Common parameter of [`server.listen()`][]
    functions.
  * `exclusive` {boolean} **Default:** `false`
  * `readableAll` {boolean} For IPC servers makes the pipe readable
    for all users. **Default:** `false`.
  * `writableAll` {boolean} For IPC servers makes the pipe writable
    for all users. **Default:** `false`.
  * `ipv6Only` {boolean} For TCP servers, setting `ipv6Only` to `true` will
    disable dual-stack support, i.e., binding to host `::` won't make
    `0.0.0.0` be bound. **Default:** `false`.
* `callback` {Function}
  functions.
* Returns: {net.Server}

If `port` is specified, it behaves the same as
<a href="#net_server_listen_port_host_backlog_callback">
<code>server.listen([port[, host[, backlog]]][, callback])</code></a>.
Otherwise, if `path` is specified, it behaves the same as
[`server.listen(path[, backlog][, callback])`][`server.listen(path)`].
If none of them is specified, an error will be thrown.

If `exclusive` is `false` (default), then cluster workers will use the same
underlying handle, allowing connection handling duties to be shared. When
`exclusive` is `true`, the handle is not shared, and attempted port sharing
results in an error. An example which listens on an exclusive port is
shown below.

```js
server.listen({
  host: 'localhost',
  port: 80,
  exclusive: true
});
```

Starting an IPC server as root may cause the server path to be inaccessible for
unprivileged users. Using `readableAll` and `writableAll` will make the server
accessible for all users.

#### `server.listen(path[, backlog][, callback])`

* `path` {string} Path the server should listen to. See
  [Identifying paths for IPC connections][].
* `backlog` {number} Common parameter of [`server.listen()`][] functions.
* `callback` {Function}.
* Returns: {net.Server}

Start an [IPC][] server listening for connections on the given `path`.

#### `server.listen([port[, host[, backlog]]][, callback])`

* `port` {number}
* `host` {string}
* `backlog` {number} Common parameter of [`server.listen()`][] functions.
* `callback` {Function}.
* Returns: {net.Server}

Start a TCP server listening for connections on the given `port` and `host`.

If `port` is omitted or is 0, the operating system will assign an arbitrary
unused port, which can be retrieved by using `server.address().port`
after the [`'listening'`][] event has been emitted.

If `host` is omitted, the server will accept connections on the
[unspecified IPv6 address][] (`::`) when IPv6 is available, or the
[unspecified IPv4 address][] (`0.0.0.0`) otherwise.

In most operating systems, listening to the [unspecified IPv6 address][] (`::`)
may cause the `net.Server` to also listen on the [unspecified IPv4 address][]
(`0.0.0.0`).

### `server.listening`

* {boolean} Indicates whether or not the server is listening for connections.

### `server.maxConnections`

* {integer}

Set this property to reject connections when the server's connection count gets
high.

It is not recommended to use this option once a socket has been sent to a child
with [`child_process.fork()`][].

### `server.ref()`

* Returns: {net.Server}

Opposite of `unref()`, calling `ref()` on a previously `unref`ed server will
*not* let the program exit if it's the only server left (the default behavior).
If the server is `ref`ed calling `ref()` again will have no effect.

### `server.unref()`

* Returns: {net.Server}

Calling `unref()` on a server will allow the program to exit if this is the only
active server in the event system. If the server is already `unref`ed calling
`unref()` again will have no effect.

## Class: `net.Socket`

* Extends: {stream.Duplex}

This class is an abstraction of a TCP socket or a streaming [IPC][] endpoint
(uses named pipes on Windows, and Unix domain sockets otherwise). It is also
an [`EventEmitter`][].

A `net.Socket` can be created by the user and used directly to interact with
a server. For example, it is returned by [`net.createConnection()`][],
so the user can use it to talk to the server.

It can also be created by Node.js and passed to the user when a connection
is received. For example, it is passed to the listeners of a
[`'connection'`][] event emitted on a [`net.Server`][], so the user can use
it to interact with the client.

### `new net.Socket([options])`

* `options` {Object} Available options are:
  * `fd` {number} If specified, wrap around an existing socket with
    the given file descriptor, otherwise a new socket will be created.
  * `allowHalfOpen` {boolean} Indicates whether half-opened TCP connections
    are allowed. See [`net.createServer()`][] and the [`'end'`][] event
    for details. **Default:** `false`.
  * `readable` {boolean} Allow reads on the socket when an `fd` is passed,
    otherwise ignored. **Default:** `false`.
  * `writable` {boolean} Allow writes on the socket when an `fd` is passed,
    otherwise ignored. **Default:** `false`.
* Returns: {net.Socket}

Creates a new socket object.

The newly created socket can be either a TCP socket or a streaming [IPC][]
endpoint, depending on what it [`connect()`][`socket.connect()`] to.

### Event: `'close'`

* `hadError` {boolean} `true` if the socket had a transmission error.

Emitted once the socket is fully closed. The argument `hadError` is a boolean
which says if the socket was closed due to a transmission error.

### Event: `'connect'`

Emitted when a socket connection is successfully established.
See [`net.createConnection()`][].

### Event: `'data'`

* {Buffer|string}

Emitted when data is received. The argument `data` will be a `Buffer` or
`String`. Encoding of data is set by [`socket.setEncoding()`][].

The data will be lost if there is no listener when a `Socket`
emits a `'data'` event.

### Event: `'drain'`

Emitted when the write buffer becomes empty. Can be used to throttle uploads.

See also: the return values of `socket.write()`.

### Event: `'end'`

Emitted when the other end of the socket sends a FIN packet, thus ending the
readable side of the socket.

By default (`allowHalfOpen` is `false`) the socket will send a FIN packet
back and destroy its file descriptor once it has written out its pending
write queue. However, if `allowHalfOpen` is set to `true`, the socket will
not automatically [`end()`][`socket.end()`] its writable side, allowing the
user to write arbitrary amounts of data. The user must call
[`end()`][`socket.end()`] explicitly to close the connection (i.e. sending a
FIN packet back).

### Event: `'error'`

* {Error}

Emitted when an error occurs. The `'close'` event will be called directly
following this event.

### Event: `'lookup'`

Emitted after resolving the host name but before connecting.
Not applicable to Unix sockets.

* `err` {Error|null} The error object. See [`dns.lookup()`][].
* `address` {string} The IP address.
* `family` {string|null} The address type. See [`dns.lookup()`][].
* `host` {string} The host name.

### Event: `'ready'`

Emitted when a socket is ready to be used.

Triggered immediately after `'connect'`.

### Event: `'timeout'`

Emitted if the socket times out from inactivity. This is only to notify that
the socket has been idle. The user must manually close the connection.

See also: [`socket.setTimeout()`][].

### `socket.address()`

* Returns: {Object}

Returns the bound `address`, the address `family` name and `port` of the
socket as reported by the operating system:
`{ port: 12346, family: 'IPv4', address: '127.0.0.1' }`

### `socket.bufferSize`

* {integer}

This property shows the number of characters buffered for writing. The buffer
may contain strings whose length after encoding is not yet known. So this number
is only an approximation of the number of bytes in the buffer.

`net.Socket` has the property that `socket.write()` always works. This is to
help users get up and running quickly. The computer cannot always keep up
with the amount of data that is written to a socket. The network connection
simply might be too slow. Node.js will internally queue up the data written to a
socket and send it out over the wire when it is possible.

The consequence of this internal buffering is that memory may grow.
Users who experience large or growing `bufferSize` should attempt to
"throttle" the data flows in their program with
[`socket.pause()`][] and [`socket.resume()`][].

### `socket.bytesRead`

* {integer}

The amount of received bytes.

### `socket.bytesWritten`

* {integer}

The amount of bytes sent.

### `socket.connect()`

Initiate a connection on a given socket.

Possible signatures:

* [`socket.connect(options[, connectListener])`][`socket.connect(options)`]
* [`socket.connect(path[, connectListener])`][`socket.connect(path)`]
  for [IPC][] connections.
* [`socket.connect(port[, host][, connectListener])`][`socket.connect(port)`]
  for TCP connections.
* Returns: {net.Socket} The socket itself.

This function is asynchronous. When the connection is established, the
[`'connect'`][] event will be emitted. If there is a problem connecting,
instead of a [`'connect'`][] event, an [`'error'`][] event will be emitted with
the error passed to the [`'error'`][] listener.
The last parameter `connectListener`, if supplied, will be added as a listener
for the [`'connect'`][] event **once**.

This function should only be used for reconnecting a socket after
`'close'` has been emitted or otherwise it may lead to undefined
behavior.

#### `socket.connect(options[, connectListener])`

* `options` {Object}
* `connectListener` {Function} Common parameter of [`socket.connect()`][]
  methods. Will be added as a listener for the [`'connect'`][] event once.
* Returns: {net.Socket} The socket itself.

Initiate a connection on a given socket. Normally this method is not needed,
the socket should be created and opened with [`net.createConnection()`][]. Use
this only when implementing a custom Socket.

For TCP connections, available `options` are:

* `port` {number} Required. Port the socket should connect to.
* `host` {string} Host the socket should connect to. **Default:** `'localhost'`.
* `localAddress` {string} Local address the socket should connect from.
* `localPort` {number} Local port the socket should connect from.
* `family` {number}: Version of IP stack. Must be `4`, `6`, or `0`. The value
  `0` indicates that both IPv4 and IPv6 addresses are allowed. **Default:** `0`.
* `hints` {number} Optional [`dns.lookup()` hints][].
* `lookup` {Function} Custom lookup function. **Default:** [`dns.lookup()`][].

For [IPC][] connections, available `options` are:

* `path` {string} Required. Path the client should connect to.
  See [Identifying paths for IPC connections][]. If provided, the TCP-specific
  options above are ignored.

For both types, available `options` include:

* `onread` {Object} If specified, incoming data is stored in a single `buffer`
  and passed to the supplied `callback` when data arrives on the socket.
  This will cause the streaming functionality to not provide any data.
  The socket will emit events like `'error'`, `'end'`, and `'close'`
  as usual. Methods like `pause()` and `resume()` will also behave as
  expected.
  * `buffer` {Buffer|Uint8Array|Function} Either a reusable chunk of memory to
    use for storing incoming data or a function that returns such.
  * `callback` {Function} This function is called for every chunk of incoming
    data. Two arguments are passed to it: the number of bytes written to
    `buffer` and a reference to `buffer`. Return `false` from this function to
    implicitly `pause()` the socket. This function will be executed in the
    global context.

Following is an example of a client using the `onread` option:

```js
const net = require('net');
net.connect({
  port: 80,
  onread: {
    // Reuses a 4KiB Buffer for every read from the socket.
    buffer: Buffer.alloc(4 * 1024),
    callback: function(nread, buf) {
      // Received data is available in `buf` from 0 to `nread`.
      console.log(buf.toString('utf8', 0, nread));
    }
  }
});
```

#### `socket.connect(path[, connectListener])`

* `path` {string} Path the client should connect to. See
  [Identifying paths for IPC connections][].
* `connectListener` {Function} Common parameter of [`socket.connect()`][]
  methods. Will be added as a listener for the [`'connect'`][] event once.
* Returns: {net.Socket} The socket itself.

Initiate an [IPC][] connection on the given socket.

Alias to
[`socket.connect(options[, connectListener])`][`socket.connect(options)`]
called with `{ path: path }` as `options`.

#### `socket.connect(port[, host][, connectListener])`

* `port` {number} Port the client should connect to.
* `host` {string} Host the client should connect to.
* `connectListener` {Function} Common parameter of [`socket.connect()`][]
  methods. Will be added as a listener for the [`'connect'`][] event once.
* Returns: {net.Socket} The socket itself.

Initiate a TCP connection on the given socket.

Alias to
[`socket.connect(options[, connectListener])`][`socket.connect(options)`]
called with `{port: port, host: host}` as `options`.

### `socket.connecting`

* {boolean}

If `true`,
[`socket.connect(options[, connectListener])`][`socket.connect(options)`] was
called and has not yet finished. It will stay `true` until the socket becomes
connected, then it is set to `false` and the `'connect'` event is emitted. Note
that the
[`socket.connect(options[, connectListener])`][`socket.connect(options)`]
callback is a listener for the `'connect'` event.

### `socket.destroy([error])`

* `error` {Object}
* Returns: {net.Socket}

Ensures that no more I/O activity happens on this socket.
Destroys the stream and closes the connection.

See [`writable.destroy()`][] for further details.

### `socket.destroyed`

* {boolean} Indicates if the connection is destroyed or not. Once a
  connection is destroyed no further data can be transferred using it.

See [`writable.destroyed`][] for further details.

### `socket.end([data[, encoding]][, callback])`

* `data` {string|Buffer|Uint8Array}
* `encoding` {string} Only used when data is `string`. **Default:** `'utf8'`.
* `callback` {Function} Optional callback for when the socket is finished.
* Returns: {net.Socket} The socket itself.

Half-closes the socket. i.e., it sends a FIN packet. It is possible the
server will still send some data.

See [`writable.end()`][] for further details.

### `socket.localAddress`

* {string}

The string representation of the local IP address the remote client is
connecting on. For example, in a server listening on `'0.0.0.0'`, if a client
connects on `'192.168.1.1'`, the value of `socket.localAddress` would be
`'192.168.1.1'`.

### `socket.localPort`

* {integer}

The numeric representation of the local port. For example, `80` or `21`.

### `socket.pause()`

* Returns: {net.Socket} The socket itself.

Pauses the reading of data. That is, [`'data'`][] events will not be emitted.
Useful to throttle back an upload.

### `socket.pending`

* {boolean}

This is `true` if the socket is not connected yet, either because `.connect()`
has not yet been called or because it is still in the process of connecting
(see [`socket.connecting`][]).

### `socket.ref()`

* Returns: {net.Socket} The socket itself.

Opposite of `unref()`, calling `ref()` on a previously `unref`ed socket will
*not* let the program exit if it's the only socket left (the default behavior).
If the socket is `ref`ed calling `ref` again will have no effect.

### `socket.remoteAddress`

* {string}

The string representation of the remote IP address. For example,
`'74.125.127.100'` or `'2001:4860:a005::68'`. Value may be `undefined` if
the socket is destroyed (for example, if the client disconnected).

### `socket.remoteFamily`

* {string}

The string representation of the remote IP family. `'IPv4'` or `'IPv6'`.

### `socket.remotePort`

* {integer}

The numeric representation of the remote port. For example, `80` or `21`.

### `socket.resume()`

* Returns: {net.Socket} The socket itself.

Resumes reading after a call to [`socket.pause()`][].

### `socket.setEncoding([encoding])`

* `encoding` {string}
* Returns: {net.Socket} The socket itself.

Set the encoding for the socket as a [Readable Stream][]. See
[`readable.setEncoding()`][] for more information.

### `socket.setKeepAlive([enable][, initialDelay])`

* `enable` {boolean} **Default:** `false`
* `initialDelay` {number} **Default:** `0`
* Returns: {net.Socket} The socket itself.

Enable/disable keep-alive functionality, and optionally set the initial
delay before the first keepalive probe is sent on an idle socket.

Set `initialDelay` (in milliseconds) to set the delay between the last
data packet received and the first keepalive probe. Setting `0` for
`initialDelay` will leave the value unchanged from the default
(or previous) setting.

### `socket.setNoDelay([noDelay])`

* `noDelay` {boolean} **Default:** `true`
* Returns: {net.Socket} The socket itself.

Enable/disable the use of Nagle's algorithm.

When a TCP connection is created, it will have Nagle's algorithm enabled.

Nagle's algorithm delays data before it is sent via the network. It attempts
to optimize throughput at the expense of latency.

Passing `true` for `noDelay` or not passing an argument will disable Nagle's
algorithm for the socket. Passing `false` for `noDelay` will enable Nagle's
algorithm.

### `socket.setTimeout(timeout[, callback])`

* `timeout` {number}
* `callback` {Function}
* Returns: {net.Socket} The socket itself.

Sets the socket to timeout after `timeout` milliseconds of inactivity on
the socket. By default `net.Socket` do not have a timeout.

When an idle timeout is triggered the socket will receive a [`'timeout'`][]
event but the connection will not be severed. The user must manually call
[`socket.end()`][] or [`socket.destroy()`][] to end the connection.

```js
socket.setTimeout(3000);
socket.on('timeout', () => {
  console.log('socket timeout');
  socket.end();
});
```

If `timeout` is 0, then the existing idle timeout is disabled.

The optional `callback` parameter will be added as a one-time listener for the
[`'timeout'`][] event.

### `socket.unref()`

* Returns: {net.Socket} The socket itself.

Calling `unref()` on a socket will allow the program to exit if this is the only
active socket in the event system. If the socket is already `unref`ed calling
`unref()` again will have no effect.

### `socket.write(data[, encoding][, callback])`

* `data` {string|Buffer|Uint8Array}
* `encoding` {string} Only used when data is `string`. **Default:** `utf8`.
* `callback` {Function}
* Returns: {boolean}

Sends data on the socket. The second parameter specifies the encoding in the
case of a string. It defaults to UTF8 encoding.

Returns `true` if the entire data was flushed successfully to the kernel
buffer. Returns `false` if all or part of the data was queued in user memory.
[`'drain'`][] will be emitted when the buffer is again free.

The optional `callback` parameter will be executed when the data is finally
written out, which may not be immediately.

See `Writable` stream [`write()`][stream_writable_write] method for more
information.

## `net.connect()`

Aliases to
[`net.createConnection()`][`net.createConnection()`].

Possible signatures:

* [`net.connect(options[, connectListener])`][`net.connect(options)`]
* [`net.connect(path[, connectListener])`][`net.connect(path)`] for [IPC][]
  connections.
* [`net.connect(port[, host][, connectListener])`][`net.connect(port, host)`]
  for TCP connections.

### `net.connect(options[, connectListener])`

* `options` {Object}
* `connectListener` {Function}
* Returns: {net.Socket}

Alias to
[`net.createConnection(options[, connectListener])`][`net.createConnection(options)`].

### `net.connect(path[, connectListener])`

* `path` {string}
* `connectListener` {Function}
* Returns: {net.Socket}

Alias to
[`net.createConnection(path[, connectListener])`][`net.createConnection(path)`].

### `net.connect(port[, host][, connectListener])`

* `port` {number}
* `host` {string}
* `connectListener` {Function}
* Returns: {net.Socket}

Alias to
[`net.createConnection(port[, host][, connectListener])`][`net.createConnection(port, host)`].

## `net.createConnection()`

A factory function, which creates a new [`net.Socket`][],
immediately initiates connection with [`socket.connect()`][],
then returns the `net.Socket` that starts the connection.

When the connection is established, a [`'connect'`][] event will be emitted
on the returned socket. The last parameter `connectListener`, if supplied,
will be added as a listener for the [`'connect'`][] event **once**.

Possible signatures:

* [`net.createConnection(options[, connectListener])`][`net.createConnection(options)`]
* [`net.createConnection(path[, connectListener])`][`net.createConnection(path)`]
  for [IPC][] connections.
* [`net.createConnection(port[, host][, connectListener])`][`net.createConnection(port, host)`]
  for TCP connections.

The [`net.connect()`][] function is an alias to this function.

### `net.createConnection(options[, connectListener])`

* `options` {Object} Required. Will be passed to both the
  [`new net.Socket([options])`][`new net.Socket(options)`] call and the
  [`socket.connect(options[, connectListener])`][`socket.connect(options)`]
  method.
* `connectListener` {Function} Common parameter of the
  [`net.createConnection()`][] functions. If supplied, will be added as
  a listener for the [`'connect'`][] event on the returned socket once.
* Returns: {net.Socket} The newly created socket used to start the connection.

For available options, see
[`new net.Socket([options])`][`new net.Socket(options)`]
and [`socket.connect(options[, connectListener])`][`socket.connect(options)`].

Additional options:

* `timeout` {number} If set, will be used to call
  [`socket.setTimeout(timeout)`][] after the socket is created, but before
  it starts the connection.

Following is an example of a client of the echo server described
in the [`net.createServer()`][] section:

```js
const net = require('net');
const client = net.createConnection({ port: 8124 }, () => {
  // 'connect' listener.
  console.log('connected to server!');
  client.write('world!\r\n');
});
client.on('data', (data) => {
  console.log(data.toString());
  client.end();
});
client.on('end', () => {
  console.log('disconnected from server');
});
```

To connect on the socket `/tmp/echo.sock`:

```js
const client = net.createConnection({ path: '/tmp/echo.sock' });
```

### `net.createConnection(path[, connectListener])`

* `path` {string} Path the socket should connect to. Will be passed to
  [`socket.connect(path[, connectListener])`][`socket.connect(path)`].
  See [Identifying paths for IPC connections][].
* `connectListener` {Function} Common parameter of the
  [`net.createConnection()`][] functions, an "once" listener for the
  `'connect'` event on the initiating socket. Will be passed to
  [`socket.connect(path[, connectListener])`][`socket.connect(path)`].
* Returns: {net.Socket} The newly created socket used to start the connection.

Initiates an [IPC][] connection.

This function creates a new [`net.Socket`][] with all options set to default,
immediately initiates connection with
[`socket.connect(path[, connectListener])`][`socket.connect(path)`],
then returns the `net.Socket` that starts the connection.

### `net.createConnection(port[, host][, connectListener])`

* `port` {number} Port the socket should connect to. Will be passed to
  [`socket.connect(port[, host][, connectListener])`][`socket.connect(port)`].
* `host` {string} Host the socket should connect to. Will be passed to
  [`socket.connect(port[, host][, connectListener])`][`socket.connect(port)`].
   **Default:** `'localhost'`.
* `connectListener` {Function} Common parameter of the
  [`net.createConnection()`][] functions, an "once" listener for the
  `'connect'` event on the initiating socket. Will be passed to
  [`socket.connect(port[, host][, connectListener])`][`socket.connect(port)`].
* Returns: {net.Socket} The newly created socket used to start the connection.

Initiates a TCP connection.

This function creates a new [`net.Socket`][] with all options set to default,
immediately initiates connection with
[`socket.connect(port[, host][, connectListener])`][`socket.connect(port)`],
then returns the `net.Socket` that starts the connection.

## `net.createServer([options][, connectionListener])`

* `options` {Object}
  * `allowHalfOpen` {boolean} Indicates whether half-opened TCP
    connections are allowed. **Default:** `false`.
  * `pauseOnConnect` {boolean} Indicates whether the socket should be
    paused on incoming connections. **Default:** `false`.
* `connectionListener` {Function} Automatically set as a listener for the
  [`'connection'`][] event.
* Returns: {net.Server}

Creates a new TCP or [IPC][] server.

If `allowHalfOpen` is set to `true`, when the other end of the socket
sends a FIN packet, the server will only send a FIN packet back when
[`socket.end()`][] is explicitly called, until then the connection is
half-closed (non-readable but still writable). See [`'end'`][] event
and [RFC 1122][half-closed] (section 4.2.2.13) for more information.

If `pauseOnConnect` is set to `true`, then the socket associated with each
incoming connection will be paused, and no data will be read from its handle.
This allows connections to be passed between processes without any data being
read by the original process. To begin reading data from a paused socket, call
[`socket.resume()`][].

The server can be a TCP server or an [IPC][] server, depending on what it
[`listen()`][`server.listen()`] to.

Here is an example of an TCP echo server which listens for connections
on port 8124:

```js
const net = require('net');
const server = net.createServer((c) => {
  // 'connection' listener.
  console.log('client connected');
  c.on('end', () => {
    console.log('client disconnected');
  });
  c.write('hello\r\n');
  c.pipe(c);
});
server.on('error', (err) => {
  throw err;
});
server.listen(8124, () => {
  console.log('server bound');
});
```

Test this by using `telnet`:

```console
$ telnet localhost 8124
```

To listen on the socket `/tmp/echo.sock`:

```js
server.listen('/tmp/echo.sock', () => {
  console.log('server bound');
});
```

Use `nc` to connect to a Unix domain socket server:

```console
$ nc -U /tmp/echo.sock
```

## `net.isIP(input)`

* `input` {string}
* Returns: {integer}

Tests if input is an IP address. Returns `0` for invalid strings,
returns `4` for IP version 4 addresses, and returns `6` for IP version 6
addresses.

## `net.isIPv4(input)`

* `input` {string}
* Returns: {boolean}

Returns `true` if input is a version 4 IP address, otherwise returns `false`.

## `net.isIPv6(input)`

* `input` {string}
* Returns: {boolean}

Returns `true` if input is a version 6 IP address, otherwise returns `false`.

[IPC]: #net_ipc_support
[Identifying paths for IPC connections]: #net_identifying_paths_for_ipc_connections
[Readable Stream]: stream.html#stream_class_stream_readable
[`'close'`]: #net_event_close
[`'connect'`]: #net_event_connect
[`'connection'`]: #net_event_connection
[`'data'`]: #net_event_data
[`'drain'`]: #net_event_drain
[`'end'`]: #net_event_end
[`'error'`]: #net_event_error_1
[`'listening'`]: #net_event_listening
[`'timeout'`]: #net_event_timeout
[`EventEmitter`]: events.html#events_class_eventemitter
[`child_process.fork()`]: child_process.html#child_process_child_process_fork_modulepath_args_options
[`dns.lookup()` hints]: dns.html#dns_supported_getaddrinfo_flags
[`dns.lookup()`]: dns.html#dns_dns_lookup_hostname_options_callback
[`net.Server`]: #net_class_net_server
[`net.Socket`]: #net_class_net_socket
[`net.connect()`]: #net_net_connect
[`net.connect(options)`]: #net_net_connect_options_connectlistener
[`net.connect(path)`]: #net_net_connect_path_connectlistener
[`net.connect(port, host)`]: #net_net_connect_port_host_connectlistener
[`net.createConnection()`]: #net_net_createconnection
[`net.createConnection(options)`]: #net_net_createconnection_options_connectlistener
[`net.createConnection(path)`]: #net_net_createconnection_path_connectlistener
[`net.createConnection(port, host)`]: #net_net_createconnection_port_host_connectlistener
[`net.createServer()`]: #net_net_createserver_options_connectionlistener
[`new net.Socket(options)`]: #net_new_net_socket_options
[`readable.setEncoding()`]: stream.html#stream_readable_setencoding_encoding
[`server.close()`]: #net_server_close_callback
[`server.getConnections()`]: #net_server_getconnections_callback
[`server.listen()`]: #net_server_listen
[`server.listen(handle)`]: #net_server_listen_handle_backlog_callback
[`server.listen(options)`]: #net_server_listen_options_callback
[`server.listen(path)`]: #net_server_listen_path_backlog_callback
[`socket(7)`]: https://man7.org/linux/man-pages/man7/socket.7.html
[`socket.connect()`]: #net_socket_connect
[`socket.connect(options)`]: #net_socket_connect_options_connectlistener
[`socket.connect(path)`]: #net_socket_connect_path_connectlistener
[`socket.connect(port)`]: #net_socket_connect_port_host_connectlistener
[`socket.connecting`]: #net_socket_connecting
[`socket.destroy()`]: #net_socket_destroy_error
[`socket.end()`]: #net_socket_end_data_encoding_callback
[`socket.pause()`]: #net_socket_pause
[`socket.resume()`]: #net_socket_resume
[`socket.setEncoding()`]: #net_socket_setencoding_encoding
[`socket.setTimeout()`]: #net_socket_settimeout_timeout_callback
[`socket.setTimeout(timeout)`]: #net_socket_settimeout_timeout_callback
[`writable.destroyed`]: stream.html#stream_writable_destroyed
[`writable.destroy()`]: stream.html#stream_writable_destroy_error
[`writable.end()`]: stream.html#stream_writable_end_chunk_encoding_callback
[half-closed]: https://tools.ietf.org/html/rfc1122
[stream_writable_write]: stream.html#stream_writable_write_chunk_encoding_callback
[unspecified IPv4 address]: https://en.wikipedia.org/wiki/0.0.0.0
[unspecified IPv6 address]: https://en.wikipedia.org/wiki/IPv6_address#Unspecified_address

cmd: