Stability: 3 - Stable

To use the HTTP server and client one must `require('http')`.

The HTTP interfaces in Node are designed to support many features

of the protocol which have been traditionally difficult to use.

In particular, large, possibly chunk-encoded, messages. The interface is

careful to never buffer entire requests or responses--the

user is able to stream data.

HTTP message headers are represented by an object like this:

{ 'content-length': '123',

'content-type': 'text/plain',

'connection': 'keep-alive',

'accept': '*/*' }

Keys are lowercased. Values are not modified.

In order to support the full spectrum of possible HTTP applications, Node's

HTTP API is very low-level. It deals with stream handling and message

parsing only. It parses a message into headers and body but it does not

parse the actual headers or the body.

## http.STATUS_CODES

* {Object}

A collection of all the standard HTTP response status codes, and the

short description of each. For example, `http.STATUS_CODES[404] === 'Not

Found'`.

## http.createServer([requestListener])

Returns a new web server object.

The `requestListener` is a function which is automatically

added to the `'request'` event.

## http.createClient([port], [host])

This function is **deprecated**; please use [http.request()][] instead.

Constructs a new HTTP client. `port` and `host` refer to the server to be

connected to.

### Event: 'request'

`function (request, response) { }`

an instance of `http.ServerResponse`

### Event: 'connection'

`net.Socket`. Usually users will not want to access this event. In

particular, the socket will not emit `readable` events because of how

the protocol parser attaches to the socket. The `socket` can also be

accessed at `request.connection`.

### Event: 'close'

### Event: 'checkContinue'

Emitted each time a request with an http Expect: 100-continue is received.

If this event isn't listened for, the server will automatically respond

with a 100 Continue as appropriate.

Handling this event involves calling `response.writeContinue` if the client

should continue to send the request body, or generating an appropriate HTTP

response (e.g., 400 Bad Request) if the client should not continue to send the

request body.

Note that when this event is emitted and handled, the `request` event will

not be emitted.

### Event: 'connect'

Emitted each time a client requests a http CONNECT method. If this event isn't

listened for, then clients requesting a CONNECT method will have their

connections closed.

* `request` is the arguments for the http request, as it is in the request

event.

* `socket` is the network socket between the server and client.

* `head` is an instance of Buffer, the first packet of the tunneling stream,

this may be empty.

After this event is emitted, the request's socket will not have a `data`

event listener, meaning you will need to bind to it in order to handle data

sent to the server on that socket.

### Event: 'upgrade'

Emitted each time a client requests a http upgrade. If this event isn't

listened for, then clients requesting an upgrade will have their connections

closed.

* `request` is the arguments for the http request, as it is in the request

event.

* `head` is an instance of Buffer, the first packet of the upgraded stream,

this may be empty.

After this event is emitted, the request's socket will not have a `data`

event listener, meaning you will need to bind to it in order to handle data

sent to the server on that socket.

### Event: 'clientError'

If a client connection emits an 'error' event - it will forwarded here.

`socket` is the `net.Socket` object that the error originated from.

Begin accepting connections on the specified port and hostname. If the

hostname is omitted, the server will accept connections directed to any

IPv4 address (`INADDR_ANY`).

To listen to a unix socket, supply a filename instead of port and hostname.

Backlog is the maximum length of the queue of pending connections.

The actual length will be determined by your OS through sysctl settings such as

`tcp_max_syn_backlog` and `somaxconn` on linux. The default value of this

parameter is 511 (not 512).

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

Start a UNIX socket server listening for connections on the given `path`.

* `handle` {Object}

The `handle` object can be set to either a server or socket (anything

with an underlying `_handle` member), or a `{fd: <n>}` object.

This will cause the server to accept connections on the specified

handle, but it is presumed that the file descriptor or handle has

already been bound to a port or domain socket.

Listening on a file descriptor is not supported on Windows.

This function is asynchronous. The last parameter `callback` will be added as

a listener for the ['listening'](net.html#event_listening_) event.

### server.maxHeadersCount

Limits maximum incoming headers count, equal to 1000 by default. If set to 0 -

no limit will be applied.

* `msecs` {Number}

* `callback` {Function}

Sets the timeout value for sockets, and emits a `'timeout'` event on

the Server object, passing the socket as an argument, if a timeout

occurs.

If there is a `'timeout'` event listener on the Server object, then it

will be called with the timed-out socket as an argument.

By default, the Server's timeout value is 2 minutes, and sockets are

destroyed automatically if they time out. However, if you assign a

callback to the Server's `'timeout'` event, then you are responsible

for handling socket timeouts.

### server.timeout

* {Number} Default = 120000 (2 minutes)

The number of milliseconds of inactivity before a socket is presumed

to have timed out.

Note that the socket timeout logic is set up on connection, so

changing this value only affects *new* connections to the server, not

any existing connections.

Set to 0 to disable any kind of automatic timeout behavior on incoming

connections.

This object is created internally by a HTTP server--not by the user. It is

passed as the second parameter to the `'request'` event.

The response implements the [Writable Stream][] interface. This is an

[EventEmitter][] with the following events:

### Event: 'close'

`function () { }`

`response.end()` was called or able to flush.

### response.writeContinue()

Sends a HTTP/1.1 100 Continue message to the client, indicating that

### response.writeHead(statusCode, [reasonPhrase], [headers])

Sends a response header to the request. The status code is a 3-digit HTTP

status code, like `404`. The last argument, `headers`, are the response headers.

Optionally one can give a human-readable `reasonPhrase` as the second

argument.

Example:

var body = 'hello world';

response.writeHead(200, {

'Content-Length': body.length,

This method must only be called once on a message and it must

be called before `response.end()` is called.

If you call `response.write()` or `response.end()` before calling this, the

implicit/mutable headers will be calculated and call this function for you.

Note: that Content-Length is given in bytes not characters. The above example

works because the string `'hello world'` contains only single byte characters.

If the body contains higher coded characters then `Buffer.byteLength()`

should be used to determine the number of bytes in a given encoding.

And Node does not check whether Content-Length and the length of the body

which has been transmitted are equal or not.

### response.setTimeout(msecs, callback)

* `msecs` {Number}

* `callback` {Function}

Sets the Socket's timeout value to `msecs`. If a callback is

provided, then it is added as a listener on the `'timeout'` event on

the response object.

If no `'timeout'` listener is added to the request, the response, or

the server, then sockets are destroyed when they time out. If you

assign a handler on the request, the response, or the server's

`'timeout'` events, then it is your responsibility to handle timed out

sockets.

### response.statusCode

When using implicit headers (not calling `response.writeHead()` explicitly), this property

flushed.

Example:

response.statusCode = 404;

After response header was sent to the client, this property indicates the

status code which was sent out.

### response.setHeader(name, value)

Sets a single header value for implicit headers. If this header already exists

here if you need to send multiple headers with the same name.

Example:

response.setHeader("Content-Type", "text/html");

or

response.setHeader("Set-Cookie", ["type=ninja", "language=javascript"]);

### response.headersSent

Boolean (read-only). True if headers were sent, false otherwise.

### response.sendDate

the response if it is not already present in the headers. Defaults to true.

This should only be disabled for testing; HTTP requires the Date header

in responses.

### response.getHeader(name)

Reads out a header that's already been queued but not sent to the client. Note

that the name is case insensitive. This can only be called before headers get

implicitly flushed.

Example:

var contentType = response.getHeader('content-type');

### response.removeHeader(name)

Removes a header that's queued for implicit sending.

Example:

response.removeHeader("Content-Encoding");

If this method is called and `response.writeHead()` has not been called, it will

switch to implicit header mode and flush the implicit headers.

This sends a chunk of the response body. This method may

be called multiple times to provide successive parts of the body.

`chunk` can be a string or a buffer. If `chunk` is a string,

the second parameter specifies how to encode it into a byte stream.

By default the `encoding` is `'utf8'`.

**Note**: This is the raw HTTP body and has nothing to do with

higher-level multi-part body encodings that may be used.

The first time `response.write()` is called, it will send the buffered

header information and the first body to the client. The second time

`response.write()` is called, Node assumes you're going to be streaming

data, and sends that separately. That is, the response is buffered up to the

first chunk of body.

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.

### response.addTrailers(headers)

This method adds HTTP trailing headers (a header but at the end of the

response; if it is not (e.g., if the request was HTTP/1.0), they will

be silently discarded.

Note that HTTP requires the `Trailer` header to be sent if you intend to

emit trailers, with a list of the header fields in its value. E.g.,

response.writeHead(200, { 'Content-Type': 'text/plain',

response.write(fileData);

response.addTrailers({'Content-MD5': "7895bf4b8828b55ceaf47747b4bca667"});

response.end();

### response.end([data], [encoding])

This method signals to the server that all of the response headers and body

The method, `response.end()`, MUST be called on each

response.

If `data` is specified, it is equivalent to calling `response.write(data, encoding)`

followed by `response.end()`.

This function allows one to transparently issue requests.

`options` can be an object or a string. If `options` is a string, it is

- `method`: A string specifying the HTTP request method. Defaults to `'GET'`.

- `path`: Request path. Defaults to `'/'`. Should include query string if any.

E.G. `'/index.html?page=12'`. An exception is thrown when the request path

contains illegal characters. Currently, only spaces are rejected but that

may change in the future.

- `auth`: Basic authentication i.e. `'user:password'` to compute an

Authorization header.

- `agent`: Controls [Agent][] behavior. When an Agent is used request will

default to `Connection: keep-alive`. Possible values:

- `undefined` (default): use [global Agent][] for this host and port.

- `false`: opts out of connection pooling with an Agent, defaults request to

`Connection: close`.

- `keepAlive`: {Boolean} Keep sockets around in a pool to be used

by other requests in the future. Default = `false`

- `keepAliveMsecs`: {Integer} When using HTTP KeepAlive, how often to

send TCP KeepAlive packets over sockets being kept alive. Default =

`1000`. Only relevant if `keepAlive` is set to `true`.

`http.request()` returns an instance of the `http.ClientRequest`

class. The `ClientRequest` instance is a writable stream. If one needs to

upload a file with a POST request, then write to the `ClientRequest` object.

Example:

var options = {

port: 80,

path: '/upload',

method: 'POST'

};

var req = http.request(options, function(res) {

console.log('STATUS: ' + res.statusCode);

console.log('HEADERS: ' + JSON.stringify(res.headers));

res.setEncoding('utf8');

res.on('data', function (chunk) {

console.log('BODY: ' + chunk);

});

});

req.on('error', function(e) {

console.log('problem with request: ' + e.message);

});

// write data to request body

req.write('data\n');

req.write('data\n');

req.end();

Note that in the example `req.end()` was called. With `http.request()` one

must always call `req.end()` to signify that you're done with the request -

even if there is no data being written to the request body.

If any error is encountered during the request (be that with DNS resolution,

TCP level errors, or actual HTTP parse errors) an `'error'` event is emitted

on the returned request object.

There are a few special headers that should be noted.

* Sending a 'Connection: keep-alive' will notify Node that the connection to

the server should be persisted until the next request.

* Sending a 'Content-length' header will disable the default chunked encoding.

Usually, when sending 'Expect: 100-continue', you should both set a timeout

and listen for the `continue` event. See RFC2616 Section 8.2.3 for more

information.

to compute basic authentication.

## http.get(options, callback)

Since most requests are GET requests without bodies, Node provides this

convenience method. The only difference between this method and `http.request()`

is that it sets the method to GET and calls `req.end()` automatically.

Example:

console.log("Got response: " + res.statusCode);

}).on('error', function(e) {

console.log("Got error: " + e.message);

});

The HTTP Agent is used for pooling sockets used in HTTP client

requests.

The HTTP Agent also defaults client requests to using

Connection:keep-alive. If no pending HTTP requests are waiting on a

socket to become free the socket is closed. This means that Node's

pool has the benefit of keep-alive when under load but still does not

require developers to manually close the HTTP clients using

KeepAlive.

If you opt into using HTTP KeepAlive, you can create an Agent object

with that flag set to `true`. (See the [constructor

options](#http_new_agent_options) below.) Then, the Agent will keep

unused sockets in a pool for later use. They will be explicitly

marked so as to not keep the Node process running. However, it is

still a good idea to explicitly [`destroy()`](#http_agent_destroy)

KeepAlive agents when they are no longer in use, so that the Sockets

will be shut down.

Sockets are removed from the agent's pool when the socket emits either

a "close" event or a special "agentRemove" event. This means that if

you intend to keep one HTTP request open for a long time and don't

want it to stay in the pool you can do something along the lines of:

http.get(options, function(res) {

// Do stuff

}).on("socket", function (socket) {

socket.emit("agentRemove");

});

Alternatively, you could just opt out of pooling entirely using

`agent:false`:

http.get({

hostname: 'localhost',

port: 80,

path: '/',

agent: false // create a new agent just for this one request

}, function (res) {

// Do stuff with response

})

### new Agent([options])

* `options` {Object} Set of configurable options to set on the agent.

Can have the following fields:

* `keepAlive` {Boolean} Keep sockets around in a pool to be used by

other requests in the future. Default = `false`

* `keepAliveMsecs` {Integer} When using HTTP KeepAlive, how often

to send TCP KeepAlive packets over sockets being kept alive.

Default = `1000`. Only relevant if `keepAlive` is set to `true`.

* `maxSockets` {Number} Maximum number of sockets to allow per

host. Default = `Infinity`.

* `maxFreeSockets` {Number} Maximum number of sockets to leave open

in a free state. Only relevant if `keepAlive` is set to `true`.

Default = `256`.

The default `http.globalAgent` that is used by `http.request` has all

of these values set to their respective defaults.

To configure any of them, you must create your own `Agent` object.

```javascript

var http = require('http');

var keepAliveAgent = new http.Agent({ keepAlive: true });

keepAliveAgent.request(options, onResponseCallback);

```

### agent.maxSockets

By default set to Infinity. Determines how many concurrent sockets the

agent can have open per host.

### agent.maxFreeSockets

By default set to 256. For Agents supporting HTTP KeepAlive, this

sets the maximum number of sockets that will be left open in the free

state.

### agent.sockets

An object which contains arrays of sockets currently in use by the

Agent. Do not modify.

### agent.freeSockets

An object which contains arrays of sockets currently awaiting use by

the Agent when HTTP KeepAlive is used. Do not modify.