HTTP | Node.js v20.1.0 Documentation

Source Code: lib/http.js

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

The HTTP interfaces in Node.js 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, so 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'
,
  
'host'
: 
'example.com'
,
  
'accept'
: 
'*/*'
 } 

Keys are lowercased. Values are not modified.

In order to support the full spectrum of possible HTTP applications, the Node.js
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.

See message.headers for details on how duplicate headers are handled.

The raw headers as they were received are retained in the rawHeaders
property, which is an array of [key, value, key2, value2, ...]. For
example, the previous message header object might have a rawHeaders
list like the following:

[ 
'ConTent-Length'
, 
'123456'
,
  
'content-LENGTH'
, 
'123'
,
  
'content-type'
, 
'text/plain'
,
  
'CONNECTION'
, 
'keep-alive'
,
  
'Host'
, 
'example.com'
,
  
'accepT'
, 
'*/*'
 ] 

Class: http.Agent#

Added in: v0.3.4

An Agent is responsible for managing connection persistence
and reuse for HTTP clients. It maintains a queue of pending requests
for a given host and port, reusing a single socket connection for each
until the queue is empty, at which time the socket is either destroyed
or put into a pool where it is kept to be used again for requests to the
same host and port. Whether it is destroyed or pooled depends on the
keepAlive option.

Pooled connections have TCP Keep-Alive enabled for them, but servers may
still close idle connections, in which case they will be removed from the
pool and a new connection will be made when a new HTTP request is made for
that host and port. Servers may also refuse to allow multiple requests
over the same connection, in which case the connection will have to be
remade for every request and cannot be pooled. The Agent will still make
the requests to that server, but each one will occur over a new connection.

When a connection is closed by the client or the server, it is removed
from the pool. Any unused sockets in the pool will be unrefed so as not
to keep the Node.js process running when there are no outstanding requests.
(see socket.unref()).

It is good practice, to destroy() an Agent instance when it is no
longer in use, because unused sockets consume OS resources.

Sockets are removed from an agent when the socket emits either
a 'close' event or an 'agentRemove' event. When intending to keep one
HTTP request open for a long time without keeping it in the agent, something
like the following may be done:

http.
get
(options, 
(
res
) => {
   
}).
on
(
'socket'
, 
(
socket
) => {
  socket.
emit
(
'agentRemove'
);
}); 

An agent may also be used for an individual request. By providing
{agent: false} as an option to the http.get() or http.request()
functions, a one-time use Agent with default options will be used
for the client connection.

agent:false:

http.
get
({
  
hostname
: 
'localhost'
,
  
port
: 
80
,
  
path
: 
'/'
,
  
agent
: 
false
,   
}, 
(
res
) => {
   
}); 

new Agent([options])#

History

VersionChanges
v15.6.0, v14.17.0

Change the default scheduling from ‘fifo’ to ‘lifo’.

v14.5.0, v12.20.0

Add scheduling option to specify the free socket scheduling strategy.

v14.5.0, v12.19.0

Add maxTotalSockets option to agent constructor.

v0.3.4

Added in: v0.3.4

• options <Object> Set of configurable options to set on the agent.
  Can have the following fields:
  • keepAlive <boolean> Keep sockets around even when there are no
    outstanding requests, so they can be used for future requests without
    having to reestablish a TCP connection. Not to be confused with the
    keep-alive value of the Connection header. The Connection: keep-alive
    header is always sent when using an agent except when the Connection
    header is explicitly specified or when the keepAlive and maxSockets
    options are respectively set to false and Infinity, in which case
    Connection: close will be used. Default: false.
  • keepAliveMsecs <number> When using the keepAlive option, specifies
    the initial delay
    for TCP Keep-Alive packets. Ignored when the
    keepAlive option is false or undefined. Default: 1000.
  • maxSockets <number> Maximum number of sockets to allow per host.
    If the same host opens multiple concurrent connections, each request
    will use new socket until the maxSockets value is reached.
    If the host attempts to open more connections than maxSockets,
    the additional requests will enter into a pending request queue, and
    will enter active connection state when an existing connection terminates.
    This makes sure there are at most maxSockets active connections at
    any point in time, from a given host.
    Default: Infinity.
  • maxTotalSockets <number> Maximum number of sockets allowed for
    all hosts in total. Each request will use a new socket
    until the maximum is reached.
    Default: Infinity.
  • maxFreeSockets <number> Maximum number of sockets per host to leave open
    in a free state. Only relevant if keepAlive is set to true.
    Default: 256.
  • scheduling <string> Scheduling strategy to apply when picking
    the next free socket to use. It can be 'fifo' or 'lifo'.
    The main difference between the two scheduling strategies is that 'lifo'
    selects the most recently used socket, while 'fifo' selects
    the least recently used socket.
    In case of a low rate of request per second, the 'lifo' scheduling
    will lower the risk of picking a socket that might have been closed
    by the server due to inactivity.
    In case of a high rate of request per second,
    the 'fifo' scheduling will maximize the number of open sockets,
    while the 'lifo' scheduling will keep it as low as possible.
    Default: 'lifo'.
  • timeout <number> Socket timeout in milliseconds.
    This will set the timeout when the socket is created.

options in socket.connect() are also supported.

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, a custom http.Agent instance must be created.

const
 http = 
require
(
'node:http'
);
const
 keepAliveAgent = 
new
 http.
Agent
({ 
keepAlive
: 
true
 });
options.
agent
 = keepAliveAgent;
http.
request
(options, onResponseCallback); 

agent.createConnection(options[, callback])#

Added in: v0.11.4

• options <Object> Options containing connection details. Check
  net.createConnection() for the format of the options
• callback <Function> Callback function that receives the created socket
• Returns: <stream.Duplex>

Produces a socket/stream to be used for HTTP requests.

By default, this function is the same as net.createConnection(). However,
custom agents may override this method in case greater flexibility is desired.

A socket/stream can be supplied in one of two ways: by returning the
socket/stream from this function, or by passing the socket/stream to callback.

This method is guaranteed to return an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specifies a socket
type other than <net.Socket>.

callback has a signature of (err, stream).

agent.keepSocketAlive(socket)#

Added in: v8.1.0

• socket <stream.Duplex>

Called when socket is detached from a request and could be persisted by the
Agent. Default behavior is to:

socket.
setKeepAlive
(
true
, 
this
.
keepAliveMsecs
);
socket.
unref
();
return
 
true
; 

This method can be overridden by a particular Agent subclass. If this
method returns a falsy value, the socket will be destroyed instead of persisting
it for use with the next request.

The socket argument can be an instance of <net.Socket>, a subclass of
<stream.Duplex>.

agent.reuseSocket(socket, request)#

Added in: v8.1.0

• socket <stream.Duplex>
• request <http.ClientRequest>

Called when socket is attached to request after being persisted because of
the keep-alive options. Default behavior is to:

socket.
ref
(); 

This method can be overridden by a particular Agent subclass.

The socket argument can be an instance of <net.Socket>, a subclass of
<stream.Duplex>.

agent.destroy()#

Added in: v0.11.4

Destroy any sockets that are currently in use by the agent.

It is usually not necessary to do this. However, if using an
agent with keepAlive enabled, then it is best to explicitly shut down
the agent when it is no longer needed. Otherwise,
sockets might stay open for quite a long time before the server
terminates them.

agent.freeSockets#

History

VersionChanges
v16.0.0

The property now has a null prototype.

v0.11.4

Added in: v0.11.4

• <Object>

An object which contains arrays of sockets currently awaiting use by
the agent when keepAlive is enabled. Do not modify.

Sockets in the freeSockets list will be automatically destroyed and
removed from the array on 'timeout'.

agent.getName([options])#

History

VersionChanges
v17.7.0, v16.15.0

The options parameter is now optional.

v0.11.4

Added in: v0.11.4

• options <Object> A set of options providing information for name generation
  • host <string> A domain name or IP address of the server to issue the
    request to
  • port <number> Port of remote server
  • localAddress <string> Local interface to bind for network connections
    when issuing the request
  • family <integer> Must be 4 or 6 if this doesn’t equal undefined.
• Returns: <string>

Get a unique name for a set of request options, to determine whether a
connection can be reused. For an HTTP agent, this returns
host:port:localAddress or host:port:localAddress:family. For an HTTPS agent,
the name includes the CA, cert, ciphers, and other HTTPS/TLS-specific options
that determine socket reusability.

agent.maxFreeSockets#

Added in: v0.11.7

• <number>

By default set to 256. For agents with keepAlive enabled, this
sets the maximum number of sockets that will be left open in the free
state.

agent.maxSockets#

Added in: v0.3.6

• <number>

By default set to Infinity. Determines how many concurrent sockets the agent
can have open per origin. Origin is the returned value of agent.getName().

agent.maxTotalSockets#

Added in: v14.5.0, v12.19.0

• <number>

By default set to Infinity. Determines how many concurrent sockets the agent
can have open. Unlike maxSockets, this parameter applies across all origins.

agent.requests#

History

VersionChanges
v16.0.0

The property now has a null prototype.

v0.5.9

Added in: v0.5.9

• <Object>

An object which contains queues of requests that have not yet been assigned to
sockets. Do not modify.

agent.sockets#

History

VersionChanges
v16.0.0

The property now has a null prototype.

v0.3.6

Added in: v0.3.6

• <Object>

An object which contains arrays of sockets currently in use by the
agent. Do not modify.

Class: http.Server#

Added in: v0.1.17

• Extends: <net.Server>

Event: 'checkContinue'#

Added in: v0.3.0

• request <http.IncomingMessage>
• response <http.ServerResponse>

Emitted each time a request with an HTTP Expect: 100-continue is received.
If this event is not 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.

When this event is emitted and handled, the 'request' event will
not be emitted.

Event: 'checkExpectation'#

Added in: v5.5.0

• request <http.IncomingMessage>
• response <http.ServerResponse>

Emitted each time a request with an HTTP Expect header is received, where the
value is not 100-continue. If this event is not listened for, the server will
automatically respond with a 417 Expectation Failed as appropriate.

When this event is emitted and handled, the 'request' event will
not be emitted.

Event: 'clientError'#

History

VersionChanges
v12.0.0

The default behavior will return a 431 Request Header Fields Too Large if a HPE_HEADER_OVERFLOW error occurs.

v9.4.0

The rawPacket is the current buffer that just parsed. Adding this buffer to the error object of 'clientError' event is to make it possible that developers can log the broken packet.

v6.0.0

The default action of calling .destroy() on the socket will no longer take place if there are listeners attached for 'clientError'.

v0.1.94

Added in: v0.1.94

• exception <Error>
• socket <stream.Duplex>

If a client connection emits an 'error' event, it will be forwarded here.
Listener of this event is responsible for closing/destroying the underlying
socket. For example, one may wish to more gracefully close the socket with a
custom HTTP response instead of abruptly severing the connection. The socket
must be closed or destroyed before the listener ends.

This event is guaranteed to be passed an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specifies a socket
type other than <net.Socket>.

Default behavior is to try close the socket with a HTTP ‘400 Bad Request’,
or a HTTP ‘431 Request Header Fields Too Large’ in the case of a
HPE_HEADER_OVERFLOW error. If the socket is not writable or headers
of the current attached http.ServerResponse has been sent, it is
immediately destroyed.

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

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

const
 server = http.
createServer
(
(
req, res
) => {
  res.
end
();
});
server.
on
(
'clientError'
, 
(
err, socket
) => {
  socket.
end
(
'HTTP/1.1 400 Bad Request\r\n\r\n'
);
});
server.
listen
(
8000
); 

When the 'clientError' event occurs, there is no request or response
object, so any HTTP response sent, including response headers and payload,
must be written directly to the socket object. Care must be taken to
ensure the response is a properly formatted HTTP response message.

err is an instance of Error with two extra columns:

• bytesParsed: the bytes count of request packet that Node.js may have parsed
  correctly;
• rawPacket: the raw packet of current request.

In some cases, the client has already received the response and/or the socket
has already been destroyed, like in case of ECONNRESET errors. Before
trying to send data to the socket, it is better to check that it is still
writable.

server.
on
(
'clientError'
, 
(
err, socket
) => {
  
if
 (err.
code
 === 
'ECONNRESET'
 || !socket.
writable
) {
    
return
;
  }

  socket.
end
(
'HTTP/1.1 400 Bad Request\r\n\r\n'
);
}); 

Event: 'close'#

Added in: v0.1.4

Emitted when the server closes.

Event: 'connect'#

Added in: v0.7.0

• request <http.IncomingMessage> Arguments for the HTTP request, as it is in
  the 'request' event
• socket <stream.Duplex> Network socket between the server and client
• head <Buffer> The first packet of the tunneling stream (may be empty)

Emitted each time a client requests an HTTP CONNECT method. If this event is
not listened for, then clients requesting a CONNECT method will have their
connections closed.

This event is guaranteed to be passed an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specifies a socket
type other than <net.Socket>.

After this event is emitted, the request’s socket will not have a 'data'
event listener, meaning it will need to be bound in order to handle data
sent to the server on that socket.

Event: 'connection'#

Added in: v0.1.0

• socket <stream.Duplex>

This event is emitted when a new TCP stream is established. socket is
typically an object of type 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.socket.

This event can also be explicitly emitted by users to inject connections
into the HTTP server. In that case, any Duplex stream can be passed.

If socket.setTimeout() is called here, the timeout will be replaced with
server.keepAliveTimeout when the socket has served a request (if
server.keepAliveTimeout is non-zero).

This event is guaranteed to be passed an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specifies a socket
type other than <net.Socket>.

Event: 'dropRequest'#

Added in: v18.7.0, v16.17.0

• request <http.IncomingMessage> Arguments for the HTTP request, as it is in
  the 'request' event
• socket <stream.Duplex> Network socket between the server and client

When the number of requests on a socket reaches the threshold of
server.maxRequestsPerSocket, the server will drop new requests
and emit 'dropRequest' event instead, then send 503 to client.

Event: 'request'#

Added in: v0.1.0

• request <http.IncomingMessage>
• response <http.ServerResponse>

Emitted each time there is a request. There may be multiple requests
per connection (in the case of HTTP Keep-Alive connections).

Event: 'upgrade'#

History

VersionChanges
v10.0.0

Not listening to this event no longer causes the socket to be destroyed if a client sends an Upgrade header.

v0.1.94

Added in: v0.1.94

• request <http.IncomingMessage> Arguments for the HTTP request, as it is in
  the 'request' event
• socket <stream.Duplex> Network socket between the server and client
• head <Buffer> The first packet of the upgraded stream (may be empty)

Emitted each time a client requests an HTTP upgrade. Listening to this event
is optional and clients cannot insist on a protocol change.

After this event is emitted, the request’s socket will not have a 'data'
event listener, meaning it will need to be bound in order to handle data
sent to the server on that socket.

This event is guaranteed to be passed an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specifies a socket
type other than <net.Socket>.

server.close([callback])#

History

VersionChanges
v19.0.0

The method closes idle connections before returning.

v0.1.90

Added in: v0.1.90

• callback <Function>

Stops the server from accepting new connections and closes all connections
connected to this server which are not sending a request or waiting for
a response.
See net.Server.close().

server.closeAllConnections()#

Added in: v18.2.0

Closes all connections connected to this server.

server.closeIdleConnections()#

Added in: v18.2.0

Closes all connections connected to this server which are not sending a request
or waiting for a response.

server.headersTimeout#

History

VersionChanges
v19.4.0, v18.14.0

The default is now set to the minimum between 60000 (60 seconds) or requestTimeout.

v11.3.0, v10.14.0

Added in: v11.3.0, v10.14.0

• <number> Default: The minimum between server.requestTimeout or 60000.

Limit the amount of time the parser will wait to receive the complete HTTP
headers.

If the timeout expires, the server responds with status 408 without
forwarding the request to the request listener and then closes the connection.

It must be set to a non-zero value (e.g. 120 seconds) to protect against
potential Denial-of-Service attacks in case the server is deployed without a
reverse proxy in front.

server.listen()#

Starts the HTTP server listening for connections.
This method is identical to server.listen() from net.Server.

server.listening#

Added in: v5.7.0

• <boolean> Indicates whether or not the server is listening for connections.

server.maxHeadersCount#

Added in: v0.7.0

• <number> Default: 2000

Limits maximum incoming headers count. If set to 0, no limit will be applied.

server.requestTimeout#

History

VersionChanges
v18.0.0

The default request timeout changed from no timeout to 300s (5 minutes).

v14.11.0

Added in: v14.11.0

• <number> Default: 300000

Sets the timeout value in milliseconds for receiving the entire request from
the client.

If the timeout expires, the server responds with status 408 without
forwarding the request to the request listener and then closes the connection.

It must be set to a non-zero value (e.g. 120 seconds) to protect against
potential Denial-of-Service attacks in case the server is deployed without a
reverse proxy in front.

server.setTimeout([msecs][, callback])#

History

VersionChanges
v13.0.0

The default timeout changed from 120s to 0 (no timeout).

v0.9.12

Added in: v0.9.12

• msecs <number> Default: 0 (no timeout)
• callback <Function>
• Returns: <http.Server>

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 does not timeout sockets. However, if a callback
is assigned to the Server’s 'timeout' event, timeouts must be handled
explicitly.

server.maxRequestsPerSocket#

Added in: v16.10.0

• <number> Requests per socket. Default: 0 (no limit)

The maximum number of requests socket can handle
before closing keep alive connection.

A value of 0 will disable the limit.

When the limit is reached it will set the Connection header value to close,
but will not actually close the connection, subsequent requests sent
after the limit is reached will get 503 Service Unavailable as a response.

server.timeout#

History

VersionChanges
v13.0.0

The default timeout changed from 120s to 0 (no timeout).

v0.9.12

Added in: v0.9.12

• <number> Timeout in milliseconds. Default: 0 (no timeout)

The number of milliseconds of inactivity before a socket is presumed
to have timed out.

A value of 0 will disable the timeout behavior on incoming connections.

The socket timeout logic is set up on connection, so changing this
value only affects new connections to the server, not any existing connections.

server.keepAliveTimeout#

Added in: v8.0.0

• <number> Timeout in milliseconds. Default: 5000 (5 seconds).

The number of milliseconds of inactivity a server needs to wait for additional
incoming data, after it has finished writing the last response, before a socket
will be destroyed. If the server receives new data before the keep-alive
timeout has fired, it will reset the regular inactivity timeout, i.e.,
server.timeout.

A value of 0 will disable the keep-alive timeout behavior on incoming
connections.
A value of 0 makes the http server behave similarly to Node.js versions prior
to 8.0.0, which did not have a keep-alive timeout.

The socket timeout logic is set up on connection, so changing this value only
affects new connections to the server, not any existing connections.

Class: http.ServerResponse#

Added in: v0.1.17

• Extends: <http.OutgoingMessage>

This object is created internally by an HTTP server, not by the user. It is
passed as the second parameter to the 'request' event.

Event: 'close'#

Added in: v0.6.7

Indicates that the response is completed, or its underlying connection was
terminated prematurely (before the response completion).

Event: 'finish'#

Added in: v0.3.6

Emitted when the response has been sent. More specifically, this event is
emitted when the last segment of the response headers and body have been
handed off to the operating system for transmission over the network. It
does not imply that the client has received anything yet.

response.addTrailers(headers)#

Added in: v0.3.0

• headers <Object>

This method adds HTTP trailing headers (a header but at the end of the
message) to the response.

Trailers will only be emitted if chunked encoding is used for the
response; if it is not (e.g. if the request was HTTP/1.0), they will
be silently discarded.

HTTP requires the Trailer header to be sent in order to
emit trailers, with a list of the header fields in its value. E.g.,

response.
writeHead
(
200
, { 
'Content-Type'
: 
'text/plain'
,
                          
'Trailer'
: 
'Content-MD5'
 });
response.
write
(fileData);
response.
addTrailers
({ 
'Content-MD5'
: 
'7895bf4b8828b55ceaf47747b4bca667'
 });
response.
end
(); 

Attempting to set a header field name or value that contains invalid characters
will result in a TypeError being thrown.

response.connection#

Added in: v0.3.0

Deprecated since: v13.0.0

Stability: 0 – Deprecated. Use response.socket

• <stream.Duplex>

See response.socket.

response.cork()#

Added in: v13.2.0, v12.16.0

See writable.cork().

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

History

VersionChanges
v15.0.0

The data parameter can now be a Uint8Array.

v10.0.0

This method now returns a reference to ServerResponse.

v0.1.90

Added in: v0.1.90

• data <string> | <Buffer> | <Uint8Array>
• encoding <string>
• callback <Function>
• Returns: <this>

This method signals to the server that all of the response headers and body
have been sent; that server should consider this message complete.
The method, response.end(), MUST be called on each response.

If data is specified, it is similar in effect to calling
response.write(data, encoding) followed by response.end(callback).

If callback is specified, it will be called when the response stream
is finished.

response.finished#

Added in: v0.0.2

Deprecated since: v13.4.0, v12.16.0

Stability: 0 – Deprecated. Use response.writableEnded

• <boolean>

The response.finished property will be true if response.end()
has been called.

response.flushHeaders()#

Added in: v1.6.0

Flushes the response headers. See also: request.flushHeaders().

response.getHeader(name)#

Added in: v0.4.0

• name <string>
• Returns: <any>

Reads out a header that’s already been queued but not sent to the client.
The name is case-insensitive. The type of the return value depends
on the arguments provided to response.setHeader().

response.
setHeader
(
'Content-Type'
, 
'text/html'
);
response.
setHeader
(
'Content-Length'
, 
Buffer
.
byteLength
(body));
response.
setHeader
(
'Set-Cookie'
, [
'type=ninja'
, 
'language=javascript'
]);
const
 contentType = response.
getHeader
(
'content-type'
);
 
const
 contentLength = response.
getHeader
(
'Content-Length'
);
 
const
 setCookie = response.
getHeader
(
'set-cookie'
);
 

response.getHeaderNames()#

Added in: v7.7.0

• Returns: <string[]>

Returns an array containing the unique names of the current outgoing headers.
All header names are lowercase.

response.
setHeader
(
'Foo'
, 
'bar'
);
response.
setHeader
(
'Set-Cookie'
, [
'foo=bar'
, 
'bar=baz'
]);

const
 headerNames = response.
getHeaderNames
();
 

response.getHeaders()#

Added in: v7.7.0

• Returns: <Object>

Returns a shallow copy of the current outgoing headers. Since a shallow copy
is used, array values may be mutated without additional calls to various
header-related http module methods. The keys of the returned object are the
header names and the values are the respective header values. All header names
are lowercase.

The object returned by the response.getHeaders() method does not
prototypically inherit from the JavaScript Object. This means that typical
Object methods such as obj.toString(), obj.hasOwnProperty(), and others
are not defined and will not work.

response.
setHeader
(
'Foo'
, 
'bar'
);
response.
setHeader
(
'Set-Cookie'
, [
'foo=bar'
, 
'bar=baz'
]);

const
 headers = response.
getHeaders
();
 

response.hasHeader(name)#

Added in: v7.7.0

• name <string>
• Returns: <boolean>

Returns true if the header identified by name is currently set in the
outgoing headers. The header name matching is case-insensitive.

const
 hasContentType = response.
hasHeader
(
'content-type'
); 

response.headersSent#

Added in: v0.9.3

• <boolean>

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

response.removeHeader(name)#

Added in: v0.4.0

• name <string>

Removes a header that’s queued for implicit sending.

response.
removeHeader
(
'Content-Encoding'
); 

response.req#

Added in: v15.7.0

• <http.IncomingMessage>

A reference to the original HTTP request object.

response.sendDate

Added in: v0.7.5

• <boolean>

When true, the Date header will be automatically generated and sent in
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.setHeader(name, value)#

Added in: v0.4.0

• name <string>
• value <any>
• Returns: <http.ServerResponse>

Returns the response object.

Sets a single header value for implicit headers. If this header already exists
in the to-be-sent headers, its value will be replaced. Use an array of strings
here to send multiple headers with the same name. Non-string values will be
stored without modification. Therefore, response.getHeader() may return
non-string values. However, the non-string values will be converted to strings
for network transmission. The same response object is returned to the caller,
to enable call chaining.

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

or

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

Attempting to set a header field name or value that contains invalid characters
will result in a TypeError being thrown.

When headers have been set with response.setHeader(), they will be merged
with any headers passed to response.writeHead(), with the headers passed
to response.writeHead() given precedence.

 
const
 server = http.
createServer
(
(
req, res
) => {
  res.
setHeader
(
'Content-Type'
, 
'text/html'
);
  res.
setHeader
(
'X-Foo'
, 
'bar'
);
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'text/plain'
 });
  res.
end
(
'ok'
);
}); 

If response.writeHead() method is called and this method has not been
called, it will directly write the supplied header values onto the network
channel without caching internally, and the response.getHeader() on the
header will not yield the expected result. If progressive population of headers
is desired with potential future retrieval and modification, use
response.setHeader() instead of response.writeHead().

response.setTimeout(msecs[, callback])#

Added in: v0.9.12

• msecs <number>
• callback <Function>
• Returns: <http.ServerResponse>

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 a handler is
assigned to the request, the response, or the server’s 'timeout' events,
timed out sockets must be handled explicitly.

response.socket#

Added in: v0.3.0

• <stream.Duplex>

Reference to the underlying socket. Usually users will not want to access
this property. In particular, the socket will not emit 'readable' events
because of how the protocol parser attaches to the socket. After
response.end(), the property is nulled.

const
 http = 
require
(
'node:http'
);
const
 server = http.
createServer
(
(
req, res
) => {
  
const
 ip = res.
socket
.
remoteAddress
;
  
const
 port = res.
socket
.
remotePort
;
  res.
end
(
`Your IP address is 
${ip}
 and your source port is 
${port}
.`);
}).
listen
(
3000
); 

This property is guaranteed to be an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specified a socket
type other than <net.Socket>.

response.statusCode#

Added in: v0.4.0

• <number> Default: 200

When using implicit headers (not calling response.writeHead() explicitly),
this property controls the status code that will be sent to the client when
the headers get flushed.

response.
statusCode
 = 
404
; 

After response header was sent to the client, this property indicates the
status code which was sent out.

response.statusMessage#

Added in: v0.11.8

• <string>

When using implicit headers (not calling response.writeHead() explicitly),
this property controls the status message that will be sent to the client when
the headers get flushed. If this is left as undefined then the standard
message for the status code will be used.

response.
statusMessage
 = 
'Not found'
; 

After response header was sent to the client, this property indicates the
status message which was sent out.

response.strictContentLength#

Added in: v18.10.0, v16.18.0

• <boolean> Default: false

If set to true, Node.js will check whether the Content-Length
header value and the size of the body, in bytes, are equal.
Mismatching the Content-Length header value will result
in an Error being thrown, identified by code: 'ERR_HTTP_CONTENT_LENGTH_MISMATCH'.

response.uncork()#

Added in: v13.2.0, v12.16.0

See writable.uncork().

response.writableEnded#

Added in: v12.9.0

• <boolean>

Is true after response.end() has been called. This property
does not indicate whether the data has been flushed, for this use
response.writableFinished instead.

response.writableFinished#

Added in: v12.7.0

• <boolean>

Is true if all data has been flushed to the underlying system, immediately
before the 'finish' event is emitted.

response.write(chunk[, encoding][, callback])#

History

VersionChanges
v15.0.0

The chunk parameter can now be a Uint8Array.

v0.1.29

Added in: v0.1.29

• chunk <string> | <Buffer> | <Uint8Array>
• encoding <string> Default: 'utf8'
• callback <Function>
• Returns: <boolean>

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.

In the node:http module, the response body is omitted when the
request is a HEAD request. Similarly, the 204 and 304 responses
must not include a message 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.
callback will be called when this chunk of data is flushed.

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 chunk of the body to the client. The second
time response.write() is called, Node.js assumes data will be streamed,
and sends the new data separately. That is, the response is buffered up to the
first chunk of the 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 free again.

response.writeContinue()#

Added in: v0.3.0

Sends an HTTP/1.1 100 Continue message to the client, indicating that
the request body should be sent. See the 'checkContinue' event on
Server.

response.writeEarlyHints(hints[, callback])#

History

VersionChanges
v18.11.0

Allow passing hints as an object.

v18.11.0

Added in: v18.11.0

• hints <Object>
• callback <Function>

Sends an HTTP/1.1 103 Early Hints message to the client with a Link header,
indicating that the user agent can preload/preconnect the linked resources.
The hints is an object containing the values of headers to be sent with
early hints message. The optional callback argument will be called when
the response message has been written.

Example

const
 earlyHintsLink = 
'</styles.css>; rel=preload; as=style'
;
response.
writeEarlyHints
({
  
'link'
: earlyHintsLink,
});

const
 earlyHintsLinks = [
  
'</styles.css>; rel=preload; as=style'
,
  
'</scripts.js>; rel=preload; as=script'
,
];
response.
writeEarlyHints
({
  
'link'
: earlyHintsLinks,
  
'x-trace-id'
: 
'id for diagnostics'
,
});

const
 
earlyHintsCallback
 = (
) => 
console
.
log
(
'early hints message sent'
);
response.
writeEarlyHints
({
  
'link'
: earlyHintsLinks,
}, earlyHintsCallback); 

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

History

VersionChanges
v14.14.0

Allow passing headers as an array.

v11.10.0, v10.17.0

Return this from writeHead() to allow chaining with end().

v5.11.0, v4.4.5

A RangeError is thrown if statusCode is not a number in the range [100, 999].

v0.1.30

Added in: v0.1.30

• statusCode <number>
• statusMessage <string>
• headers <Object> | <Array>
• Returns: <http.ServerResponse>

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 statusMessage as the second
argument.

headers may be an Array where the keys and values are in the same list.
It is not a list of tuples. So, the even-numbered offsets are key values,
and the odd-numbered offsets are the associated values. The array is in the same
format as request.rawHeaders.

Returns a reference to the ServerResponse, so that calls can be chained.

const
 body = 
'hello world'
;
response
  .
writeHead
(
200
, {
    
'Content-Length'
: 
Buffer
.
byteLength
(body),
    
'Content-Type'
: 
'text/plain'
,
  })
  .
end
(body); 

This method must only be called once on a message and it must
be called before response.end() is called.

If response.write() or response.end() are called before calling
this, the implicit/mutable headers will be calculated and call this function.

When headers have been set with response.setHeader(), they will be merged
with any headers passed to response.writeHead(), with the headers passed
to response.writeHead() given precedence.

If this method is called and response.setHeader() has not been called,
it will directly write the supplied header values onto the network channel
without caching internally, and the response.getHeader() on the header
will not yield the expected result. If progressive population of headers is
desired with potential future retrieval and modification, use
response.setHeader() instead.

 
const
 server = http.
createServer
(
(
req, res
) => {
  res.
setHeader
(
'Content-Type'
, 
'text/html'
);
  res.
setHeader
(
'X-Foo'
, 
'bar'
);
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'text/plain'
 });
  res.
end
(
'ok'
);
}); 

Content-Length is read in bytes, not characters. Use
Buffer.byteLength() to determine the length of the body in bytes. Node.js
will check whether Content-Length and the length of the body which has
been transmitted are equal or not.

Attempting to set a header field name or value that contains invalid characters
will result in a [Error][] being thrown.

response.writeProcessing()#

Added in: v10.0.0

Sends a HTTP/1.1 102 Processing message to the client, indicating that
the request body should be sent.

Class: http.IncomingMessage#

History

VersionChanges
v15.5.0

The destroyed value returns true after the incoming data is consumed.

v13.1.0, v12.16.0

The readableHighWaterMark value mirrors that of the socket.

v0.1.17

Added in: v0.1.17

• Extends: <stream.Readable>

An IncomingMessage object is created by http.Server or
http.ClientRequest and passed as the first argument to the 'request'
and 'response' event respectively. It may be used to access response
status, headers, and data.

Different from its socket value which is a subclass of <stream.Duplex>, the
IncomingMessage itself extends <stream.Readable> and is created separately to
parse and emit the incoming HTTP headers and payload, as the underlying socket
may be reused multiple times in case of keep-alive.

Event: 'aborted'#

Added in: v0.3.8

Deprecated since: v17.0.0, v16.12.0

'close' event instead.Stability: 0 – Deprecated. Listen forevent instead.

Emitted when the request has been aborted.

Event: 'close'#

History

VersionChanges
v16.0.0

The close event is now emitted when the request has been completed and not when the underlying socket is closed.

v0.4.2

Added in: v0.4.2

Emitted when the request has been completed.

message.aborted#

Added in: v10.1.0

Deprecated since: v17.0.0, v16.12.0

message.destroyed from Stability: 0 – Deprecated. Checkfrom <stream.Readable>

• <boolean>

The message.aborted property will be true if the request has
been aborted.

message.complete#

Added in: v0.3.0

• <boolean>

The message.complete property will be true if a complete HTTP message has
been received and successfully parsed.

This property is particularly useful as a means of determining if a client or
server fully transmitted a message before a connection was terminated:

const
 req = http.
request
({
  
host
: 
'127.0.0.1'
,
  
port
: 
8080
,
  
method
: 
'POST'
,
}, 
(
res
) => {
  res.
resume
();
  res.
on
(
'end'
, 
() =>
 {
    
if
 (!res.
complete
)
      
console
.
error
(
        
'The connection was terminated while the message was still being sent'
);
  });
}); 

message.connection#

Added in: v0.1.90

Deprecated since: v16.0.0

Stability: 0 – Deprecated. Use message.socket

Alias for message.socket.

message.destroy([error])#

History

VersionChanges
v14.5.0, v12.19.0

The function returns this for consistency with other Readable streams.

v0.3.0

Added in: v0.3.0

• error <Error>
• Returns: <this>

Calls destroy() on the socket that received the IncomingMessage. If error
is provided, an 'error' event is emitted on the socket and error is passed
as an argument to any listeners on the event.

message.headers#

History

VersionChanges
v19.5.0, v18.14.0

The joinDuplicateHeaders option in the http.request() and http.createServer() functions ensures that duplicate headers are not discarded, but rather combined using a comma separator, in accordance with RFC 9110 Section 5.3.

v15.1.0

message.headers is now lazily computed using an accessor property on the prototype and is no longer enumerable.

v0.1.5

Added in: v0.1.5

• <Object>

The request/response headers object.

Key-value pairs of header names and values. Header names are lower-cased.

 
 
 
 
 
console
.
log
(request.
headers
); 

Duplicates in raw headers are handled in the following ways, depending on the
header name:

• Duplicates of age, authorization, content-length, content-type,
  etag, expires, from, host, if-modified-since, if-unmodified-since,
  last-modified, location, max-forwards, proxy-authorization, referer,
  retry-after, server, or user-agent are discarded.
  To allow duplicate values of the headers listed above to be joined,
  use the option joinDuplicateHeaders in http.request()
  and http.createServer(). See RFC 9110 Section 5.3 for more
  information.
• set-cookie is always an array. Duplicates are added to the array.
• For duplicate cookie headers, the values are joined together with ; .
• For all other headers, the values are joined together with , .

message.headersDistinct#

Added in: v18.3.0, v16.17.0

• <Object>

Similar to message.headers, but there is no join logic and the values are
always arrays of strings, even for headers received just once.

 
 
 
 
 
console
.
log
(request.
headersDistinct
); 

message.httpVersion#

Added in: v0.1.1

• <string>

In case of server request, the HTTP version sent by the client. In the case of
client response, the HTTP version of the connected-to server.
Probably either '1.1' or '1.0'.

Also message.httpVersionMajor is the first integer and
message.httpVersionMinor is the second.

message.method#

Added in: v0.1.1

• <string>

Only valid for request obtained from http.Server.

The request method as a string. Read only. Examples: 'GET', 'DELETE'.

message.rawHeaders#

Added in: v0.11.6

• <string[]>

The raw request/response headers list exactly as they were received.

The keys and values are in the same list. It is not a
list of tuples. So, the even-numbered offsets are key values, and the
odd-numbered offsets are the associated values.

Header names are not lowercased, and duplicates are not merged.

 
 
 
 
 
 
 
 
 
 
console
.
log
(request.
rawHeaders
); 

message.rawTrailers#

Added in: v0.11.6

• <string[]>

The raw request/response trailer keys and values exactly as they were
received. Only populated at the 'end' event.

message.setTimeout(msecs[, callback])#

Added in: v0.5.9

• msecs <number>
• callback <Function>
• Returns: <http.IncomingMessage>

Calls message.socket.setTimeout(msecs, callback).

message.socket#

Added in: v0.3.0

• <stream.Duplex>

The net.Socket object associated with the connection.

With HTTPS support, use request.socket.getPeerCertificate() to obtain the
client’s authentication details.

This property is guaranteed to be an instance of the <net.Socket> class,
a subclass of <stream.Duplex>, unless the user specified a socket
type other than <net.Socket> or internally nulled.

message.statusCode#

Added in: v0.1.1

• <number>

Only valid for response obtained from http.ClientRequest.

The 3-digit HTTP response status code. E.G. 404.

message.statusMessage#

Added in: v0.11.10

• <string>

Only valid for response obtained from http.ClientRequest.

The HTTP response status message (reason phrase). E.G. OK or Internal Server Error.

message.trailers#

Added in: v0.3.0

• <Object>

The request/response trailers object. Only populated at the 'end' event.

message.trailersDistinct#

Added in: v18.3.0, v16.17.0

• <Object>

Similar to message.trailers, but there is no join logic and the values are
always arrays of strings, even for headers received just once.
Only populated at the 'end' event.

message.url#

Added in: v0.1.90

• <string>

Only valid for request obtained from http.Server.

Request URL string. This contains only the URL that is present in the actual
HTTP request. Take the following request:

GET
 
/status?name=ryan
  
Accept
: 
text/plain 

To parse the URL into its parts:

new
 
URL
(request.
url
, 
`http://
${request.headers.host}
`); 

When request.url is '/status?name=ryan' and request.headers.host is
'localhost:3000':

$ 
node
> 
new URL(request.url, `http://
${request.headers.host}
`)
URL {
  href: 'http://localhost:3000/status?name=ryan',
  origin: 'http://localhost:3000',
  protocol: 'http:',
  username: '',
  password: '',
  host: 'localhost:3000',
  hostname: 'localhost',
  port: '3000',
  pathname: '/status',
  search: '?name=ryan',
  searchParams: URLSearchParams { 'name' => 'ryan' },
  hash: ''
} 

Class: http.OutgoingMessage#

Added in: v0.1.17

• Extends: <Stream>

This class serves as the parent class of http.ClientRequest
and http.ServerResponse. It is an abstract outgoing message from
the perspective of the participants of an HTTP transaction.

Event: 'drain'#

Added in: v0.3.6

Emitted when the buffer of the message is free again.

Event: 'finish'#

Added in: v0.1.17

Emitted when the transmission is finished successfully.

Event: 'prefinish'#

Added in: v0.11.6

Emitted after outgoingMessage.end() is called.
When the event is emitted, all data has been processed but not necessarily
completely flushed.

outgoingMessage.addTrailers(headers)#

Added in: v0.3.0

• headers <Object>

Adds HTTP trailers (headers but at the end of the message) to the message.

Trailers will only be emitted if the message is chunked encoded. If not,
the trailers will be silently discarded.

HTTP requires the Trailer header to be sent to emit trailers,
with a list of header field names in its value, e.g.

message.
writeHead
(
200
, { 
'Content-Type'
: 
'text/plain'
,
                         
'Trailer'
: 
'Content-MD5'
 });
message.
write
(fileData);
message.
addTrailers
({ 
'Content-MD5'
: 
'7895bf4b8828b55ceaf47747b4bca667'
 });
message.
end
(); 

Attempting to set a header field name or value that contains invalid characters
will result in a TypeError being thrown.

outgoingMessage.appendHeader(name, value)#

Added in: v18.3.0, v16.17.0

• name <string> Header name
• value <string> | <string[]> Header value
• Returns: <this>

Append a single header value for the header object.

If the value is an array, this is equivalent of calling this method multiple
times.

If there were no previous value for the header, this is equivalent of calling
outgoingMessage.setHeader(name, value).

Depending of the value of options.uniqueHeaders when the client request or the
server were created, this will end up in the header being sent multiple times or
a single time with values joined using ; .

outgoingMessage.connection#

Added in: v0.3.0

Deprecated since: v15.12.0, v14.17.1

Stability: 0 – Deprecated: Use outgoingMessage.socket instead.

Alias of outgoingMessage.socket.

outgoingMessage.cork()#

Added in: v13.2.0, v12.16.0

See writable.cork().

outgoingMessage.destroy([error])#

Added in: v0.3.0

• error <Error> Optional, an error to emit with error event
• Returns: <this>

Destroys the message. Once a socket is associated with the message
and is connected, that socket will be destroyed as well.

outgoingMessage.end(chunk[, encoding][, callback])#

History

VersionChanges
v15.0.0

The chunk parameter can now be a Uint8Array.

v0.11.6

add callback argument.

v0.1.90

Added in: v0.1.90

• chunk <string> | <Buffer> | <Uint8Array>
• encoding <string> Optional, Default: utf8
• callback <Function> Optional
• Returns: <this>

Finishes the outgoing message. If any parts of the body are unsent, it will
flush them to the underlying system. If the message is chunked, it will
send the terminating chunk 0\r\n\r\n, and send the trailers (if any).

If chunk is specified, it is equivalent to calling
outgoingMessage.write(chunk, encoding), followed by
outgoingMessage.end(callback).

If callback is provided, it will be called when the message is finished
(equivalent to a listener of the 'finish' event).

outgoingMessage.flushHeaders()#

Added in: v1.6.0

Flushes the message headers.

For efficiency reason, Node.js normally buffers the message headers
until outgoingMessage.end() is called or the first chunk of message data
is written. It then tries to pack the headers and data into a single TCP
packet.

It is usually desired (it saves a TCP round-trip), but not when the first
data is not sent until possibly much later. outgoingMessage.flushHeaders()
bypasses the optimization and kickstarts the message.

outgoingMessage.getHeader(name)#

Added in: v0.4.0

• name <string> Name of header
• Returns <string> | <undefined>

Gets the value of the HTTP header with the given name. If that header is not
set, the returned value will be undefined.

outgoingMessage.getHeaderNames()#

Added in: v7.7.0

• Returns <string[]>

Returns an array containing the unique names of the current outgoing headers.
All names are lowercase.

outgoingMessage.getHeaders()#

Added in: v7.7.0

• Returns: <Object>

Returns a shallow copy of the current outgoing headers. Since a shallow
copy is used, array values may be mutated without additional calls to
various header-related HTTP module methods. The keys of the returned
object are the header names and the values are the respective header
values. All header names are lowercase.

The object returned by the outgoingMessage.getHeaders() method does
not prototypically inherit from the JavaScript Object. This means that
typical Object methods such as obj.toString(), obj.hasOwnProperty(),
and others are not defined and will not work.

outgoingMessage.
setHeader
(
'Foo'
, 
'bar'
);
outgoingMessage.
setHeader
(
'Set-Cookie'
, [
'foo=bar'
, 
'bar=baz'
]);

const
 headers = outgoingMessage.
getHeaders
();
 

outgoingMessage.hasHeader(name)#

Added in: v7.7.0

• name <string>
• Returns <boolean>

Returns true if the header identified by name is currently set in the
outgoing headers. The header name is case-insensitive.

const
 hasContentType = outgoingMessage.
hasHeader
(
'content-type'
); 

outgoingMessage.headersSent#

Added in: v0.9.3

• <boolean>

Read-only. true if the headers were sent, otherwise false.

outgoingMessage.pipe()#

Added in: v9.0.0

Overrides the stream.pipe() method inherited from the legacy Stream class
which is the parent class of http.OutgoingMessage.

Calling this method will throw an Error because outgoingMessage is a
write-only stream.

outgoingMessage.removeHeader(name)#

Added in: v0.4.0

• name <string> Header name

Removes a header that is queued for implicit sending.

outgoingMessage.
removeHeader
(
'Content-Encoding'
); 

outgoingMessage.setHeader(name, value)#

Added in: v0.4.0

• name <string> Header name
• value <any> Header value
• Returns: <this>

Sets a single header value. If the header already exists in the to-be-sent
headers, its value will be replaced. Use an array of strings to send multiple
headers with the same name.

outgoingMessage.setHeaders(headers)#

Added in: v19.6.0, v18.15.0

• headers <Headers> | <Map>
• Returns: <http.ServerResponse>

Returns the response object.

Sets multiple header values for implicit headers.
headers must be an instance of Headers or Map,
if a header already exists in the to-be-sent headers,
its value will be replaced.

const
 headers = 
new
 
Headers
({ 
foo
: 
'bar'
 });
response.
setHeaders
(headers); 

or

const
 headers = 
new
 
Map
([[
'foo'
, 
'bar'
]]);
res.
setHeaders
(headers); 

When headers have been set with outgoingMessage.setHeaders(),
they will be merged with any headers passed to response.writeHead(),
with the headers passed to response.writeHead() given precedence.

 
const
 server = http.
createServer
(
(
req, res
) => {
  
const
 headers = 
new
 
Headers
({ 
'Content-Type'
: 
'text/html'
 });
  res.
setHeaders
(headers);
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'text/plain'
 });
  res.
end
(
'ok'
);
}); 

outgoingMessage.setTimeout(msesc[, callback])#

Added in: v0.9.12

• msesc <number>
• callback <Function> Optional function to be called when a timeout
  occurs. Same as binding to the timeout event.
• Returns: <this>

Once a socket is associated with the message and is connected,
socket.setTimeout() will be called with msecs as the first parameter.

outgoingMessage.socket#

Added in: v0.3.0

• <stream.Duplex>

Reference to the underlying socket. Usually, users will not want to access
this property.

After calling outgoingMessage.end(), this property will be nulled.

outgoingMessage.uncork()#

Added in: v13.2.0, v12.16.0

See writable.uncork()

outgoingMessage.writableCorked#

Added in: v13.2.0, v12.16.0

• <number>

The number of times outgoingMessage.cork() has been called.

outgoingMessage.writableEnded#

Added in: v12.9.0

• <boolean>

Is true if outgoingMessage.end() has been called. This property does
not indicate whether the data has been flushed. For that purpose, use
message.writableFinished instead.

outgoingMessage.writableFinished#

Added in: v12.7.0

• <boolean>

Is true if all data has been flushed to the underlying system.

outgoingMessage.writableHighWaterMark#

Added in: v12.9.0

• <number>

The highWaterMark of the underlying socket if assigned. Otherwise, the default
buffer level when writable.write() starts returning false (16384).

outgoingMessage.writableLength#

Added in: v12.9.0

• <number>

The number of buffered bytes.

outgoingMessage.writableObjectMode#

Added in: v12.9.0

• <boolean>

Always false.

outgoingMessage.write(chunk[, encoding][, callback])#

History

VersionChanges
v15.0.0

The chunk parameter can now be a Uint8Array.

v0.11.6

The callback argument was added.

v0.1.29

Added in: v0.1.29

• chunk <string> | <Buffer> | <Uint8Array>
• encoding <string> Default: utf8
• callback <Function>
• Returns <boolean>

Sends a chunk of the body. This method can be called multiple times.

The encoding argument is only relevant when chunk is a string. Defaults to
'utf8'.

The callback argument is optional and will be called when this chunk of data
is flushed.

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 the user
memory. The 'drain' event will be emitted when the buffer is free again.

http.METHODS#

Added in: v0.11.8

• <string[]>

A list of the HTTP methods that are supported by the parser.

http.STATUS_CODES#

Added in: v0.1.22

• <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([options][, requestListener])#

History

VersionChanges
v20.1.0

The highWaterMark option is supported now.

v18.0.0

The requestTimeout, headersTimeout, keepAliveTimeout, and connectionsCheckingInterval options are supported now.

v18.0.0

The noDelay option now defaults to true.

v17.7.0, v16.15.0

The noDelay, keepAlive and keepAliveInitialDelay options are supported now.

v13.3.0

The maxHeaderSize option is supported now.

v13.8.0, v12.15.0, v10.19.0

The insecureHTTPParser option is supported now.

v9.6.0, v8.12.0

The options argument is supported now.

v0.1.13

Added in: v0.1.13

• options <Object>

  • connectionsCheckingInterval: Sets the interval value in milliseconds to
    check for request and headers timeout in incomplete requests.
    Default: 30000.
  • headersTimeout: Sets the timeout value in milliseconds for receiving
    the complete HTTP headers from the client.
    See server.headersTimeout for more information.
    Default: 60000.
  • highWaterMark <number> Optionally overrides all sockets’
    readableHighWaterMark and writableHighWaterMark. This affects
    highWaterMark property of both IncomingMessage and ServerResponse.
    Default: See stream.getDefaultHighWaterMark().
  • insecureHTTPParser <boolean> Use an insecure HTTP parser that accepts
    invalid HTTP headers when true. Using the insecure parser should be
    avoided. See --insecure-http-parser for more information.
    Default: false.
  • IncomingMessage <http.IncomingMessage> Specifies the IncomingMessage
    class to be used. Useful for extending the original IncomingMessage.
    Default: IncomingMessage.
  • keepAlive <boolean> If set to true, it enables keep-alive functionality
    on the socket immediately after a new incoming connection is received,
    similarly on what is done in [socket.setKeepAlive([enable][, initialDelay])][socket.setKeepAlive(enable, initialDelay)].
    Default: false.
  • keepAliveInitialDelay <number> If set to a positive number, it sets the
    initial delay before the first keepalive probe is sent on an idle socket.
    Default: 0.
  • keepAliveTimeout: The number of milliseconds of inactivity a server
    needs to wait for additional incoming data, after it has finished writing
    the last response, before a socket will be destroyed.
    See server.keepAliveTimeout for more information.
    Default: 5000.
  • maxHeaderSize <number> Optionally overrides the value of
    --max-http-header-size for requests received by this server, i.e.
    the maximum length of request headers in bytes.
    Default: 16384 (16 KiB).
  • noDelay <boolean> If set to true, it disables the use of Nagle’s
    algorithm immediately after a new incoming connection is received.
    Default: true.
  • requestTimeout: Sets the timeout value in milliseconds for receiving
    the entire request from the client.
    See server.requestTimeout for more information.
    Default: 300000.
  • requireHostHeader <boolean> It forces the server to respond with
    a 400 (Bad Request) status code to any HTTP/1.1 request message
    that lacks a Host header (as mandated by the specification).
    Default: true.
  • joinDuplicateHeaders <boolean> It joins the field line values of multiple
    headers in a request with , instead of discarding the duplicates.
    See message.headers for more information.
    Default: false.
  • ServerResponse <http.ServerResponse> Specifies the ServerResponse class
    to be used. Useful for extending the original ServerResponse. Default:
    ServerResponse.
  • uniqueHeaders <Array> A list of response headers that should be sent only
    once. If the header’s value is an array, the items will be joined
    using ; .

• requestListener <Function>

• Returns: <http.Server>

Returns a new instance of http.Server.

The requestListener is a function which is automatically
added to the 'request' event.

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

 
const
 server = http.
createServer
(
(
req, res
) => {
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'application/json'
 });
  res.
end
(
JSON
.
stringify
({
    
data
: 
'Hello World!'
,
  }));
});

server.
listen
(
8000
); 

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

 
const
 server = http.
createServer
();

 
server.
on
(
'request'
, 
(
request, res
) => {
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'application/json'
 });
  res.
end
(
JSON
.
stringify
({
    
data
: 
'Hello World!'
,
  }));
});

server.
listen
(
8000
); 

http.get(url[, options][, callback])#

History

VersionChanges
v10.9.0

The url parameter can now be passed along with a separate options object.

v7.5.0

The options parameter can be a WHATWG URL object.

v0.3.6

Added in: v0.3.6

• url <string> | <URL>
• options <Object> Accepts the same options as
  http.request(), with the method always set to GET.
  Properties that are inherited from the prototype are ignored.
• callback <Function>
• Returns: <http.ClientRequest>

Since most requests are GET requests without bodies, Node.js 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. The callback must take care to consume the response
data for reasons stated in http.ClientRequest section.

The callback is invoked with a single argument that is an instance of
http.IncomingMessage.

JSON fetching example:

http.
get
(
'http://localhost:8000/'
, 
(
res
) => {
  
const
 { statusCode } = res;
  
const
 contentType = res.
headers
[
'content-type'
];

  
let
 error;
   
   
  
if
 (statusCode !== 
200
) {
    error = 
new
 
Error
(
'Request Failed.\n'
 +
                      
`Status Code: 
${statusCode}
`);
  } 
else
 
if
 (!
/^application\/json/
.
test
(contentType)) {
    error = 
new
 
Error
(
'Invalid content-type.\n'
 +
                      
`Expected application/json but received 
${contentType}
`);
  }
  
if
 (error) {
    
console
.
error
(error.
message
);
     
    res.
resume
();
    
return
;
  }

  res.
setEncoding
(
'utf8'
);
  
let
 rawData = 
''
;
  res.
on
(
'data'
, 
(
chunk
) => { rawData += chunk; });
  res.
on
(
'end'
, 
() =>
 {
    
try
 {
      
const
 parsedData = 
JSON
.
parse
(rawData);
      
console
.
log
(parsedData);
    } 
catch
 (e) {
      
console
.
error
(e.
message
);
    }
  });
}).
on
(
'error'
, 
(
e
) => {
  
console
.
error
(
`Got error: 
${e.message}
`);
});

 
const
 server = http.
createServer
(
(
req, res
) => {
  res.
writeHead
(
200
, { 
'Content-Type'
: 
'application/json'
 });
  res.
end
(
JSON
.
stringify
({
    
data
: 
'Hello World!'
,
  }));
});

server.
listen
(
8000
); 

http.globalAgent#

History

VersionChanges
v19.0.0

The agent now uses HTTP Keep-Alive by default.

v0.5.9

Added in: v0.5.9

• <http.Agent>

Global instance of Agent which is used as the default for all HTTP client
requests.

http.maxHeaderSize#

Added in: v11.6.0, v10.15.0

• <number>

Read-only property specifying the maximum allowed size of HTTP headers in bytes.
Defaults to 16 KiB. Configurable using the --max-http-header-size CLI
option.

This can be overridden for servers and client requests by passing the
maxHeaderSize option.

http.request(url[, options][, callback])#

History

VersionChanges
v16.7.0, v14.18.0

When using a URL object parsed username and password will now be properly URI decoded.

v15.3.0, v14.17.0

It is possible to abort a request with an AbortSignal.

v13.3.0

The maxHeaderSize option is supported now.

v13.8.0, v12.15.0, v10.19.0

The insecureHTTPParser option is supported now.

v10.9.0

The url parameter can now be passed along with a separate options object.

v7.5.0

The options parameter can be a WHATWG URL object.

v0.3.6

Added in: v0.3.6

• url <string> | <URL>
• options <Object>
  • agent <http.Agent> | <boolean> Controls Agent behavior. Possible
    values:
    • undefined (default): use http.globalAgent for this host and port.
    • Agent object: explicitly use the passed in Agent.
    • false: causes a new Agent with default values to be used.
  • auth <string> Basic authentication ('user:password') to compute an
    Authorization header.
  • createConnection <Function> A function that produces a socket/stream to
    use for the request when the agent option is not used. This can be used to
    avoid creating a custom Agent class just to override the default
    createConnection function. See agent.createConnection() for more
    details. Any Duplex stream is a valid return value.
  • defaultPort <number> Default port for the protocol. Default:
    agent.defaultPort if an Agent is used, else undefined.
  • family <number> IP address family to use when resolving host or
    hostname. Valid values are 4 or 6. When unspecified, both IP v4 and
    v6 will be used.
  • headers <Object> An object containing request headers.
  • hints <number> Optional dns.lookup() hints.
  • host <string> A domain name or IP address of the server to issue the
    request to. Default: 'localhost'.
  • hostname <string> Alias for host. To support url.parse(),
    hostname will be used if both host and hostname are specified.
  • insecureHTTPParser <boolean> Use an insecure HTTP parser that accepts
    invalid HTTP headers when true. Using the insecure parser should be
    avoided. See --insecure-http-parser for more information.
    Default: false
  • localAddress <string> Local interface to bind for network connections.
  • localPort <number> Local port to connect from.
  • lookup <Function> Custom lookup function. Default: dns.lookup().
  • maxHeaderSize <number> Optionally overrides the value of
    --max-http-header-size (the maximum length of response headers in
    bytes) for responses received from the server.
    Default: 16384 (16 KiB).
  • method <string> A string specifying the HTTP request method. Default:
    'GET'.
  • path <string> Request path. 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. Default: '/'.
  • port <number> Port of remote server. Default: defaultPort if set,
    else 80.
  • protocol <string> Protocol to use. Default: 'http:'.
  • setHost <boolean>: Specifies whether or not to automatically add the
    Host header. Defaults to true.
  • signal <AbortSignal>: An AbortSignal that may be used to abort an ongoing
    request.
  • socketPath <string> Unix domain socket. Cannot be used if one of host
    or port is specified, as those specify a TCP Socket.
  • timeout <number>: A number specifying the socket timeout in milliseconds.
    This will set the timeout before the socket is connected.
  • uniqueHeaders <Array> A list of request headers that should be sent
    only once. If the header’s value is an array, the items will be joined
    using ; .
  • joinDuplicateHeaders <boolean> It joins the field line values of
    multiple headers in a request with , instead of discarding
    the duplicates. See message.headers for more information.
    Default: false.
• callback <Function>
• Returns: <http.ClientRequest>

options in socket.connect() are also supported.

Node.js maintains several connections per server to make HTTP requests.
This function allows one to transparently issue requests.

url can be a string or a URL object. If url is a
string, it is automatically parsed with new URL(). If it is a URL
object, it will be automatically converted to an ordinary options object.

If both url and options are specified, the objects are merged, with the
options properties taking precedence.

The optional callback parameter will be added as a one-time listener for
the 'response' event.

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.

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

const
 postData = 
JSON
.
stringify
({
  
'msg'
: 
'Hello World!'
,
});

const
 options = {
  
hostname
: 
'www.google.com'
,
  
port
: 
80
,
  
path
: 
'/upload'
,
  
method
: 
'POST'
,
  
headers
: {
    
'Content-Type'
: 
'application/json'
,
    
'Content-Length'
: 
Buffer
.
byteLength
(postData),
  },
};

const
 req = http.
request
(options, 
(
res
) => {
  
console
.
log
(
`STATUS: 
${res.statusCode}
`);
  
console
.
log
(
`HEADERS: 
${
JSON
.stringify(res.headers)}`);
  res.
setEncoding
(
'utf8'
);
  res.
on
(
'data'
, 
(
chunk
) => {
    
console
.
log
(
`BODY: 
${chunk}
`);
  });
  res.
on
(
'end'
, 
() =>
 {
    
console
.
log
(
'No more data in response.'
);
  });
});

req.
on
(
'error'
, 
(
e
) => {
  
console
.
error
(
`problem with request: 
${e.message}
`);
});

 
req.
write
(postData);
req.
end
(); 

In the example req.end() was called. With http.request() one
must always call req.end() to signify the end of 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. As with all 'error' events, if no listeners
are registered the error will be thrown.

There are a few special headers that should be noted.

• Sending a ‘Connection: keep-alive’ will notify Node.js that the connection to
  the server should be persisted until the next request.

• Sending a ‘Content-Length’ header will disable the default chunked encoding.

• Sending an ‘Expect’ header will immediately send the request headers.
  Usually, when sending ‘Expect: 100-continue’, both a timeout and a listener
  for the 'continue' event should be set. See RFC 2616 Section 8.2.3 for more
  information.

• Sending an Authorization header will override using the auth option
  to compute basic authentication.

Example using a URL as options:

const
 options = 
new
 
URL
(
'http://abc: [email protected] 
const
 req = http.
request
(options, 
(
res
) => {
   
}); 

In a successful request, the following events will be emitted in the following
order:

• 'socket'
• 'response'
  • 'data' any number of times, on the res object
    ('data' will not be emitted at all if the response body is empty, for
    instance, in most redirects)
  • 'end' on the res object
• 'close'

In the case of a connection error, the following events will be emitted:

• 'socket'
• 'error'
• 'close'

In the case of a premature connection close before the response is received,
the following events will be emitted in the following order:

• 'socket'
• 'error' with an error with message 'Error: socket hang up' and code
  'ECONNRESET'
• 'close'

In the case of a premature connection close after the response is received,
the following events will be emitted in the following order:

• 'socket'
• 'response'
  • 'data' any number of times, on the res object
• (connection closed here)
• 'aborted' on the res object
• 'error' on the res object with an error with message
  'Error: aborted' and code 'ECONNRESET'
• 'close'
• 'close' on the res object

If req.destroy() is called before a socket is assigned, the following
events will be emitted in the following order:

• (req.destroy() called here)
• 'error' with an error with message 'Error: socket hang up' and code
  'ECONNRESET', or the error with which req.destroy() was called
• 'close'

If req.destroy() is called before the connection succeeds, the following
events will be emitted in the following order:

• 'socket'
• (req.destroy() called here)
• 'error' with an error with message 'Error: socket hang up' and code
  'ECONNRESET', or the error with which req.destroy() was called
• 'close'

If req.destroy() is called after the response is received, the following
events will be emitted in the following order:

• 'socket'
• 'response'
  • 'data' any number of times, on the res object
• (req.destroy() called here)
• 'aborted' on the res object
• 'error' on the res object with an error with message 'Error: aborted'
  and code 'ECONNRESET', or the error with which req.destroy() was called
• 'close'
• 'close' on the res object

If req.abort() is called before a socket is assigned, the following
events will be emitted in the following order:

• (req.abort() called here)
• 'abort'
• 'close'

If req.abort() is called before the connection succeeds, the following
events will be emitted in the following order:

• 'socket'
• (req.abort() called here)
• 'abort'
• 'error' with an error with message 'Error: socket hang up' and code
  'ECONNRESET'
• 'close'

If req.abort() is called after the response is received, the following
events will be emitted in the following order:

• 'socket'
• 'response'
  • 'data' any number of times, on the res object
• (req.abort() called here)
• 'abort'
• 'aborted' on the res object
• 'error' on the res object with an error with message
  'Error: aborted' and code 'ECONNRESET'.
• 'close'
• 'close' on the res object

Setting the timeout option or using the setTimeout() function will
not abort the request or do anything besides add a 'timeout' event.

Passing an AbortSignal and then calling abort() on the corresponding
AbortController will behave the same way as calling .destroy() on the
request. Specifically, the 'error' event will be emitted with an error with
the message 'AbortError: The operation was aborted', the code 'ABORT_ERR'
and the cause, if one was provided.

http.validateHeaderName(name[, label])

History

VersionChanges
v19.5.0, v18.14.0

The label parameter is added.

v14.3.0

Added in: v14.3.0

• name <string>
• label <string> Label for error message. Default: 'Header name'.

Performs the low-level validations on the provided name that are done when
res.setHeader(name, value) is called.

Passing illegal value as name will result in a TypeError being thrown,
identified by code: 'ERR_INVALID_HTTP_TOKEN'.

It is not necessary to use this method before passing headers to an HTTP request
or response. The HTTP module will automatically validate such headers.
Examples:

Example:

const
 { validateHeaderName } = 
require
(
'node:http'
);

try
 {
  
validateHeaderName
(
''
);
} 
catch
 (err) {
  
console
.
error
(err 
instanceof
 
TypeError
);  
  
console
.
error
(err.
code
);  
  
console
.
error
(err.
message
);  
} 

http.validateHeaderValue(name, value)

Added in: v14.3.0

• name <string>
• value <any>

Performs the low-level validations on the provided value that are done when
res.setHeader(name, value) is called.

Passing illegal value as value will result in a TypeError being thrown.

• Undefined value error is identified by code: 'ERR_HTTP_INVALID_HEADER_VALUE'.
• Invalid value character error is identified by code: 'ERR_INVALID_CHAR'.

It is not necessary to use this method before passing headers to an HTTP request
or response. The HTTP module will automatically validate such headers.

Examples:

const
 { validateHeaderValue } = 
require
(
'node:http'
);

try
 {
  
validateHeaderValue
(
'x-my-header'
, 
undefined
);
} 
catch
 (err) {
  
console
.
error
(err 
instanceof
 
TypeError
);  
  
console
.
error
(err.
code
 === 
'ERR_HTTP_INVALID_HEADER_VALUE'
);  
  
console
.
error
(err.
message
);  
}

try
 {
  
validateHeaderValue
(
'x-my-header'
, 
'oʊmɪɡə'
);
} 
catch
 (err) {
  
console
.
error
(err 
instanceof
 
TypeError
);  
  
console
.
error
(err.
code
 === 
'ERR_INVALID_CHAR'
);  
  
console
.
error
(err.
message
);  
} 

http.setMaxIdleHTTPParsers(max)#

Added in: v18.8.0, v16.18.0

• max <number> Default: 1000.

Set the maximum number of idle HTTP parsers.