An example of a web server written with Node which responds with "Hello World" after waiting two seconds:
node.http.createServer(function (request, response) { setTimeout(function () { response.sendHeader(200, [["Content-Type", "text/plain"]]); response.sendBody("Hello World"); response.finish(); }, 2000); }).listen(8000); puts("Server running at http://127.0.0.1:8000/");
To run the server, put the code into a file called example.js
and execute
it with the node program
> node example.js Server running at http://127.0.0.1:8000/
Node provides an easy way to build scalable network programs. In the above
example, the 2 second delay does not prevent the server from handling new
requests. Node tells the operating system (through epoll
, kqueue
,
/dev/poll
, or select
) that it should be notified when the 2 seconds are
up or if a new connection is made—then it goes to sleep. If someone new
connects, then it executes the callback, if the timeout expires, it executes
the inner callback. Each connection is only a small heap allocation.
This is in contrast to today’s more common model where OS threads are employed for concurrency. Thread-based networking is relatively inefficient and very difficult to use. Node will show much better memory efficiency under high-loads than systems which allocate 2mb thread stacks for each connection. Furthermore, users of Node are free from worries of dead-locking the process—there are no locks. In fact, no function in Node directly performs I/O. Because nothing blocks, less-than-expert programmers are able to develop fast systems.
Node is similar in design to systems like Ruby’s
Event Machine
or Python’s Twisted.
Node takes the event model a bit further. For example, in other systems there
is always a blocking call to start the event-loop. Typically one defines
behavior through callbacks at the beginning of a script and at the end starts a
server through a call like EventMachine::run()
. In Node it works differently.
By default Node enters the event loop after executing the input script. Node
exits the event loop when there are no more callbacks to perform. Like in
traditional browser javascript, the event loop is hidden from the user.
Node’s HTTP API has grown out of my difficulties developing and working with web servers. For example, streaming data through most web frameworks is impossible. Or the oft-made false assumption that all message headers have unique fields. Node attempts to correct these and other problems in its API. Coupled with Node’s purely evented infrastructure, it will make a more comprehensive foundation for future web libraries/frameworks.
But what about multiple-processor concurrency? Threads are necessary to scale programs to multi-core computers. The name Node should give some hint at how it is envisioned being used. Processes are necessary to scale to multi-core computers, not memory-sharing threads. The fundamentals of scalable systems are fast networking and non-blocking design—the rest is message passing. In the future, I’d like Node to be able to spawn new processes (probably using the Web Workers API), but this is something that fits well into the current design.
Node supports 3 byte-string encodings: ASCII ("ascii"
), UTF-8 ("utf8"
),
and raw binary ("raw"
). It uses strings to represent ASCII and UTF-8
encoded data. For the moment, arrays of integers are used to represent raw
binary data—this representation is rather inefficient. This will
change in the future, when
V8 supports Blob objects.
Unless otherwise noted, functions are all asynchronous and do not block execution.
puts(string)
-
Alias for
stdout.puts()
. Outputs thestring
and a trailing new-line tostdout
.Everything in node is asynchronous;
puts()
is no exception. This might seem ridiculous but, if for example, one is pipingstdout
into an NFS file,printf()
will block from network latency. There is an internal queue forputs()
output, so you can be assured that output will be displayed in the order it was called. node.debug(string)
-
A synchronous output function. Will block the process and output the string immediately to stdout.
p(object)
-
Print the JSON representation of
object
to the standard output. print(string)
-
Like
puts()
but without the trailing new-line. node.exit(code)
-
Immediately ends the process with the specified code.
ARGV
-
An array containing the command line arguments.
stdout
,stderr
, andstdin
-
Objects of type
node.fs.File
. (See below.) __filename
-
The filename of the script being executed.
Many objects in Node emit events: a TCP server emits an event each time
there is a connection, a child process emits an event when it exits. All
objects which emit events are are instances of node.EventEmitter
.
Events are represented by a snakecased string. Here are some examples:
"connection"
, "receive"
, "message_begin"
.
Functions can be then be attached to objects, to be executed when an event is emitted. These functions are called listeners.
Some asynchronous file operations return an EventEmitter
called a
promise. A promise emits just a single event when the operation is
complete.
emitter.addListener(event, listener)
-
Adds a listener to the end of the listeners array for the specified event.
server.addListener("connection", function (socket) { puts("someone connected!"); });
emitter.listeners(event)
-
Returns an array of listeners for the specified event. This array can be manipulated, e.g. to remove listeners.
emitter.emit(event, args)
-
Execute each of the listeners in order with the array
args
as arguments.
node.Promise
inherits from node.eventEmitter
. A promise emits one of two
events: "success"
or "error"
. After emitting its event, it will not
emit anymore events.
promise.addCallback(listener)
-
Adds a listener for the
"success"
event. Returns the same promise object. promise.addErrback(listener)
-
Adds a listener for the
"error"
event. Returns the same promise object.
Node has a simple module loading system. In Node, files and modules are in
one-to-one correspondence. As an example, foo.js
loads the module
circle.js
.
The contents of foo.js
:
var circle = require("circle.js"); function onLoad () { puts("The area of a cirlce of radius 4 is " + circle.area(4)); }
The contents of circle.js
:
var PI = 3.14; exports.area = function (r) { return PI * r * r; }; exports.circumference = function (r) { return 2 * PI * r; };
The module circle.js
has exported the functions area()
and
circumference()
. To export an object, add to the special exports
object. (Alternatively, one can use this
instead of exports
.) Variables
local to the module will be private. In this example the variable PI
is
private to circle.js
.
The module path is relative to the file calling require()
. That is,
circle.js
must be in the same directory as foo.js
for require()
to
find it.
HTTP URLs can also be used to load modules. For example,
var circle = require("http://tinyclouds.org/node/circle.js");
Like require()
the function include()
also loads a module. Instead of
returning a namespace object, include()
will add the module’s exports into
the global namespace. For example:
include("circle.js"); function onLoad () { puts("The area of a cirlce of radius 4 is " + area(4)); }
Because module loading does not happen instantaneously and because Node has
a policy of never blocking, a callback onLoad
can be set that will notify
the user when the included modules are loaded. Each file/module can have
its own onLoad
callback.
include()
and require()
cannot be used after onLoad()
is called.
When the program exits a callback onExit()
will be called for each module
(children first).
The onExit()
callback cannot perform I/O since the process is going to
forcably exit in less than microsecond. However, it is a good hook to
perform constant time checks of the module’s state. E.G. for unit tests:
include("asserts.js"); var timer_executed = false; setTimeout(function () { timer_executed = true }, 1000); function onExit () { assertTrue(timer_executed); }
Just to reiterate: onExit()
, is not the place to close files or shutdown
servers. The process will exit before they get performed.
setTimeout(callback, delay)
-
To schedule execution of callback after delay milliseconds. Returns a
timeoutId
for possible use withclearTimeout()
. clearTimeout(timeoutId)
-
Prevents said timeout from triggering.
setInterval(callback, delay)
-
To schedule the repeated execution of callback everydelay milliseconds. Returns a
intervalId
for possible use withclearInterval()
. clearInterval(intervalId)
-
Stops a interval from triggering.
Node provides a tridirectional popen(3)
facility through the class
node.Process
. It is possible to stream data through the child’s stdin
,
stdout
, and stderr
in a fully non-blocking way.
Event | Parameters | Notes |
---|---|---|
|
|
Each time the child process sends data to its |
|
|
Identical to the |
|
|
This event is emitted after the child process ends. |
node.createProcess(command)
-
Launches a new process with the given
command
. For example:var ls = node.createProcess("ls -lh /usr"); ls.addListener("output", function (data) { puts(data); });
process.pid
-
The PID of the child process.
process.write(data, encoding="ascii")
-
Write data to the child process’s
stdin
. The second argument is optional and specifies the encoding: possible values are"utf8"
,"ascii"
, and"raw"
. process.close()
-
Closes the process’s
stdin
stream. process.kill(signal=node.SIGTERM)
-
Send a single to the child process. If no argument is given, the process will be sent
node.SIGTERM
. The standard POSIX signals are defined under thenode
namespace (node.SIGINT
,node.SIGUSR1
, …).
This part of the API is split into two parts: simple wrappers
around standard POSIX file I/O functions and a user-friendly
File
object.
All POSIX wrappers have a similar form.
They return a promise (node.Promise
). Example:
var promise = node.fs.unlink("/tmp/hello"); promise.addCallback(function () { puts("successfully deleted /tmp/hello"); });
There is no guaranteed ordering to the POSIX wrappers. The following is very much prone to error
node.fs.rename("/tmp/hello", "/tmp/world"); node.fs.stat("/tmp/world").addCallback(function (stats) { puts("stats: " + JSON.stringify(stats)); });
It could be that stat()
is executed before the rename()
.
The correct way to do this is to chain the promises.
node.fs.rename("/tmp/hello", "/tmp/world") .addCallback(function () { node.fs.stat("/tmp/world") .addCallback(function (stats) { puts("stats: " + JSON.stringify(stats)); }); });
node.fs.rename(path1, path2)
-
See rename(2).
-
on success: no parameters.
-
on error: no parameters.
-
node.fs.stat(path)
-
See stat(2).
-
on success: Returns
stats
object. It looks like this:{ dev: 2049, ino: 305352, mode: 16877, nlink: 12, uid: 1000, gid: 1000, rdev: 0, size: 4096, blksize: 4096, blocks: 8, atime: "2009-06-29T11:11:55Z", mtime: "2009-06-29T11:11:40Z", ctime: "2009-06-29T11:11:40Z" }
-
on error: no parameters.
-
node.fs.unlink(path)
-
See unlink(2)
-
on success: no parameters.
-
on error: no parameters.
-
node.fs.rmdir(path)
-
See rmdir(2)
-
on success: no parameters.
-
on error: no parameters.
-
node.fs.close(fd)
-
See close(2)
-
on success: no parameters.
-
on error: no parameters.
-
node.fs.open(path, flags, mode)
-
See open(2). The constants like
O_CREAT
are defined atnode.O_CREAT
.-
on success:
fd
is given as the parameter. -
on error: no parameters.
-
node.fs.write(fd, data, position)
-
Write data to the file specified by
fd
.data
is either an array of integers (for raw data) or a string for UTF-8 encoded characters.position
refers to the offset from the beginning of the file where this data should be written. Ifposition
isnull
, the data will be written at the current position. See pwrite(2).-
on success: returns an integer
written
which specifies how many bytes were written. -
on error: no parameters.
-
node.fs.read(fd, length, position, encoding)
-
Read data from the file specified by
fd
.length
is an integer specifying the number of bytes to read.position
is an integer specifying where to begin reading from in the file.encoding
is eithernode.UTF8
ornode.RAW
.-
on success: returns
data, bytes_read
, what was read from the file. -
on error: no parameters.
-
node.fs.cat(filename, encoding)
-
Outputs the entire contents of a file. Example:
node.fs.cat("/etc/passwd", "utf8").addCallback(function (content) { puts(content); });
-
on success: returns
data
, what was read from the file. -
on error: no parameters.
-
A buffered file object.
Internal request queues exist for each instance of node.fs.File
so that
multiple commands can be issued at once. Thus the following is safe:
var file = new node.fs.File(); file.open("/tmp/blah", "w+"); file.write("hello"); file.write("world"); file.close();
Here is an example of reading the first 10 bytes from /etc/passwd
and
outputting it to stdout
.
var file = new node.fs.File({encoding: "utf8"}); file.open("/etc/passwd", "r"); file.read(10).addCallback(function (chunk) { puts(chunk); }); file.close();
Event | Parameters | Notes |
---|---|---|
|
Emitted if an error happens. |
new node.fs.File(options={})
-
Creates a new file object.
The
options
argument is optional. It can contain the following fields-
fd
: a file descriptor for the file. -
encoding
: howfile.read()
should return data. Either"raw"
or"utf8"
. Defaults to"raw"
.
-
file.open(path, mode)
-
Opens the file at
path
.mode
is a string:-
"r", open for reading and writing.
-
"r+", open for only reading.
-
"w", create a new file for reading and writing; if it already exists truncate it.
-
"w+", create a new file for writing only; if it already exists truncate it.
-
"a", create a new file for writing and reading. Writes append to the end of the file.
-
"a+"
-
file.read(length, position)
-
Reads
length
bytes from the file atposition
.position
can be omitted to write at the current file position. file.write(data, position)
-
Writes
data
to the file.position
can be omitted to write at the current file position. file.close()
-
Closes the file.
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 array of 2-element arrays like this
[ ["Content-Length", "123"] , ["Content-Type", "text/plain"] , ["Connection", "keep-alive"] , ["Accept", "*/*"] ]
In order to support the full spectrum of possible HTTP applications, Node’s HTTP API is very low-level. It deals with connection handling and message parsing only. It parses a message into headers and body but it does not parse the actual headers or the body. That means, for example, that Node does not, and will never, provide API to access or manipulate Cookies or multi-part bodies. This is left to the user.
Event | Parameters | Notes |
---|---|---|
|
|
|
|
|
When a new TCP connection is established.
|
|
|
Emitted when the server closes. |
node.http.createServer(request_listener, options);
-
Returns a new web server object.
The
options
argument is optional. Theoptions
argument accepts the same values as the options argument fornode.tcp.Server
does.The
request_listener
is a function which is automatically added to the"request"
event. server.listen(port, hostname)
-
Begin accepting connections on the specified port and hostname. If the hostname is omitted, the server will accept connections directed to any address.
server.close()
-
Stops the server from accepting new connections.
This object is created internally by a HTTP server—not by
the user—and passed as the first argument to a "request"
listener.
Event | Parameters | Notes |
---|---|---|
|
|
Emitted when a piece of the message body is received. Example: A chunk of
the body is given as the single argument. The transfer-encoding has been
decoded. The body chunk is either a String in the case of UTF-8 encoding or
an array of numbers in the case of raw encoding. The body encoding is set
with |
|
Emitted exactly once for each message. No arguments. After emitted no other events will be emitted on the request. |
request.method
-
The request method as a string. Read only. Example:
"GET"
,"DELETE"
. request.uri
-
Request URI Object. This contains only the parameters that are present in the actual http request. That is, if the request is
GET /status?name=ryan HTTP/1.1\r\n Accept: */*\r\n \r\n
Then
request.uri
will be{ path: "/status", file: "status", directory: "/", params: { "name" : "ryan" } }
In particular, note that
request.uri.protocol
isundefined
. This is because there was no URI protocol given in the actual HTTP Request.request.uri.anchor
,request.uri.query
,request.uri.file
,request.uri.directory
,request.uri.path
,request.uri.relative
,request.uri.port
,request.uri.host
,request.uri.password
,request.uri.user
,request.uri.authority
,request.uri.protocol
,request.uri.params
,request.uri.toString()
,request.uri.source
request.headers
-
The request headers expressed as an array of 2-element arrays. Read only.
request.httpVersion
-
The HTTP protocol version as a string. Read only. Examples:
"1.1"
,"1.0"
request.setBodyEncoding(encoding)
-
Set the encoding for the request body. Either
"utf8"
or"raw"
. Defaults to raw. request.connection
-
The
node.http.Connection
object.
This object is created internally by a HTTP server—not by the user. It is
passed as the second parameter to the "request"
event.
response.sendHeader(statusCode, headers)
-
Sends a response header to the request. The status code is a 3-digit HTTP status code, like
404
. The second argument,headers
, should be an array of 2-element arrays, representing the response headers.Example:
var body = "hello world"; response.sendHeader(200, [ ["Content-Length", body.length], ["Content-Type", "text/plain"] ]);
This method must only be called once on a message and it must be called before
response.finish()
is called. response.sendBody(chunk, encoding="ascii")
-
This method must be called after
sendHeader
was called. It sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body.If
chunk
is a string, the second parameter specifies how to encode it into a byte stream. By default theencoding
is"ascii"
.Note: This is the raw HTTP body and has nothing to do with higher-level multi-part body encodings that may be used.
response.finish()
-
This method signals to the server that all of the response headers and body has been sent; that server should consider this message complete. The method,
response.finish()
, MUST be called on each response.
An HTTP client is constructed with a server address as its argument, the returned handle is then used to issue one or more requests. Depending on the server connected to, the client might pipeline the requests or reestablish the connection after each connection. Currently the implementation does not pipeline requests.
Example of connecting to google.com
var google = node.http.createClient(80, "google.com"); var request = google.get("/"); request.finish(function (response) { puts("STATUS: " + response.statusCode); puts("HEADERS: " + JSON.stringify(response.headers)); response.setBodyEncoding("utf8"); response.addListener("body", function (chunk) { puts("BODY: " + chunk); }); });
node.http.createClient(port, host)
-
Constructs a new HTTP client.
port
andhost
refer to the server to be connected to. A connection is not established until a request is issued. client.get(path, request_headers)
,client.head(path, request_headers)
,client.post(path, request_headers)
,client.del(path, request_headers)
,client.put(path, request_headers)
-
Issues a request; if necessary establishes connection. Returns a
node.http.ClientRequest
instance.request_headers
is optional.request_headers
should be an array of 2-element arrays. Additional request headers might be added internally by Node. Returns aClientRequest
object.Do remember to include the
Content-Length
header if you plan on sending a body. If you plan on streaming the body, perhaps setTransfer-Encoding: chunked
.Notethe request is not complete. This method only sends the header of the request. One needs to call request.finish()
to finalize the request and retrieve the response. (This sounds convoluted but it provides a chance for the user to stream a body to the server withrequest.sendBody()
.)
This object is created internally and returned from the request methods of a
node.http.Client
. It represents an in-progress request whose header has
already been sent.
Event | Parameters | Notes |
---|---|---|
|
|
Emitted when a response is received to this request. Typically the user will
set a listener to this via the |
request.sendBody(chunk, encoding="ascii")
-
Sends a sucessive peice of the body. By calling this method many times, the user can stream a request body to a server—in that case it is suggested to use the
["Transfer-Encoding", "chunked"]
header line when creating the request.The
chunk
argument should be an array of integers or a string.The
encoding
argument is optional and only applies whenchunk
is a string. The encoding argument should be either"utf8"
or"ascii"
. By default the body uses ASCII encoding, as it is faster. request.finish(response_listener)
-
Finishes sending the request. If any parts of the body are unsent, it will flush them to the socket. If the request is chunked, this will send the terminating
"0\r\n\r\n"
.The parameter
response_listener
is a callback which will be executed when the response headers have been received. Theresponse_listener
callback is executed with one argument which is an instance ofnode.http.ClientResponse
.
This object is created internally and passed to the "response"
event.
Event | Parameters | Notes |
---|---|---|
|
|
Emitted when a piece of the message body is received. Example: A chunk of
the body is given as the single argument. The transfer-encoding has been
decoded. The body chunk is either a String in the case of UTF-8 encoding or
an array of numbers in the case of raw encoding. The body encoding is set
with |
|
Emitted exactly once for each message. No arguments. After emitted no other events will be emitted on the response. |
response.statusCode
-
The 3-digit HTTP response status code. E.G.
404
. response.httpVersion
-
The HTTP version of the connected-to server. Probably either
"1.1"
or"1.0"
. response.headers
-
The response headers. An Array of 2-element arrays.
response.setBodyEncoding(encoding)
-
Set the encoding for the response body. Either
"utf8"
or"raw"
. Defaults to raw. response.client
-
A reference to the
node.http.Client
that this response belongs to.
Here is an example of a echo server which listens for connections on port 7000
function echo (socket) { socket.setEncoding("utf8"); socket.addListener("connect", function () { socket.send("hello\r\n"); }); socket.addListener("receive", function (data) { socket.send(data); }); socket.addListener("eof", function () { socket.send("goodbye\r\n"); socket.close(); }); } var server = node.tcp.createServer(echo); server.listen(7000, "localhost");
Event | Parameters | Notes |
---|---|---|
|
|
Emitted when a new connection is made.
|
|
|
Emitted when the server closes. |
node.tcp.createServer(connection_listener);
-
Creates a new TCP server.
The
connection_listener
argument is automatically set as a listener for the"connection"
event. server.listen(port, host=null, backlog=1024)
-
Tells the server to listen for TCP connections to
port
andhost
.
host
is optional. If host
is not specified the server will accept client
connections on any network address.
The third argument, backlog
, is also optional and defaults to 1024. The
backlog
argument defines the maximum length to which the queue of pending
connections for the server may grow. If a connection request arrives when
the queue is full, the client may receive a "ECONNREFUSED" error or, if the
underlying protocol supports retransmission, the request may be ignored so
that a later reattempt at connection succeeds
server.close()
-
Stops the server from accepting new connections.
This object is used as a TCP client and also as a server-side
socket for node.tcp.Server
.
Event | Parameters | Notes |
---|---|---|
|
Call once the connection is established. |
|
|
|
Called when data is received on the
connection. Encoding of data is set
by |
|
Called when the other end of the
connection sends a FIN packet.
After this is emitted the |
|
|
|
Emitted once the connection is fully
disconnected. The argument |
node.tcp.createConnection(port, host="127.0.0.1")
-
Creates a new connection object and opens a connection to the specified
port
andhost
. If the second parameter is omitted, localhost is assumed. connection.remoteAddress
-
The string representation of the remote IP address. For example,
"74.125.127.100"
or"2001:4860:a005::68"
.This member is only present in server-side connections.
connection.readyState
-
Either
"closed"
,"open"
,"opening"
,"readOnly"
, or"writeOnly"
. connection.setEncoding(encoding)
-
Sets the encoding (either
"utf8"
or"raw"
) for data that is received. connection.send(data, encoding="ascii")
-
Sends data on the connection. The data should be eithre an array of integers (for raw binary) or a string (for utf8 or ascii). The second parameter specifies the encoding in the case of a string—it defaults to ASCII because encoding to UTF8 is rather slow.
connection.close()
-
Half-closes the connection. I.E. sends a FIN packet. It is possible the server will still send some data. After calling this
readyState
will be"readOnly"
. connection.fullClose()
-
Close both ends of the connection. Data that is received after this call is responded to with RST packets. If you don’t know about this, just use
close()
. connection.forceClose()
-
Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).
Here is an example of which resolves "www.google.com"
then reverse
resolves the IP addresses which are returned.
var resolution = node.dns.resolve4("www.google.com"); resolution.addCallback(function (addresses, ttl, cname) { puts("addresses: " + JSON.stringify(addresses)); puts("ttl: " + JSON.stringify(ttl)); puts("cname: " + JSON.stringify(cname)); for (var i = 0; i < addresses.length; i++) { var a = addresses[i]; var reversing = node.dns.reverse(a); reversing.addCallback( function (domains, ttl, cname) { puts("reverse for " + a + ": " + JSON.stringify(domains)); }); reversing.addErrback( function (code, msg) { puts("reverse for " + a + " failed: " + msg); }); } }); resolution.addErrback(function (code, msg) { puts("error: " + msg); });
node.dns.resolve4(domain)
-
Resolves a domain (e.g.
"google.com"
) into an array of IPv4 addresses (e.g.["74.125.79.104","74.125.79.105","74.125.79.106","74.125.79.147","74.125.79.99","74.125.79.103"]
). This function returns a promise.-
on success: returns
addresses, ttl, cname
.ttl
(time-to-live) is an integer specifying the number of seconds this result is valid for.cname
is the canonical name for the query. -
on error: returns
code, msg
.code
is one of the error codes listed below andmsg
is a string describing the error in English.
-
node.dns.resolve6(domain)
-
The same as
node.dns.resolve4()
except for IPv6 queries (anAAAA
query). node.dns.reverse(ip)
-
Reverse resolves an ip address to an array of domain names.
-
on success: returns
domains, ttl, cname
.ttl
(time-to-live) is an integer specifying the number of seconds this result is valid for.cname
is the canonical name for the query.domains
is an array of domains. -
on error: returns
code, msg
.code
is one of the error codes listed below andmsg
is a string describing the error in English.
-
Each DNS query can return an error code.
-
node.dns.TEMPFAIL
: timeout, SERVFAIL or similar. -
node.dns.PROTOCOL
: got garbled reply. -
node.dns.NXDOMAIN
: domain does not exists. -
node.dns.NODATA
: domain exists but no data of reqd type. -
node.dns.NOMEM
: out of memory while processing. -
node.dns.BADQUERY
: the query is malformed.