NODE(1)

NAME

node - purely event-based I/O for V8 javascript

SYNOPSIS

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/

DESCRIPTION

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.

API

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.

Helpers

puts(string): Alias for stdout.puts(). Outputs the string and a trailing new-line to stdout.

Everything in node is asynchronous; puts() is no exception. This might seem ridiculous but, if for example, one is piping stdout into an NFS file, printf() will block from network latency. There is an internal queue for puts() 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.

Global Variables

ARGV: An array containing the command line arguments.
stdout, stderr, and stdin: Objects of type node.fs.File. (See below.)
__filename: The filename of the script being executed.

Events

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.

`node.EventEmitter`

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`

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.

Modules

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));
}

`onLoad()`

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.

`onExit()`

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.

Timers

setTimeout(callback, delay): To schedule execution of callback after delay milliseconds. Returns a timeoutId for possible use with clearTimeout().
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 with clearInterval().
clearInterval(intervalId): Stops a interval from triggering.

Child Processes

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.

`node.Process`

Event	Parameters	Notes
`"output"`	`data`	Each time the child process sends data to its `stdout`, this event is triggered. `data` is a string. At the moment all data passed to `stdout` is interrpreted as UTF-8 encoded. + If the child process closes its `stdout` stream (a common thing to do on exit), this event will be emitted with `data === null`.
`"error"`	`data`	Identical to the `"output"` event except for `stderr` instead of `stdout`.
`"exit"`	`code`	This event is emitted after the child process ends. `code` is the final exit code of the process. One can be assured that after this event is emitted that the `"output"` and `"error"` callbacks will no longer be made.

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 the node namespace (node.SIGINT, node.SIGUSR1, …).

File I/O

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.

POSIX Wrappers

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 at node.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. If position is null, 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 either node.UTF8 or node.RAW.

on success: returns data, bytes_read, what was read from the file.
on error: no parameters.

`node.fs.File`

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();

Event	Parameters	Notes
`"error"`		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: how file.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 at position. 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.

HTTP

The HTTP interfaces in Node are designed to support many features of the protocol which have been traditionally difficult to use. In particular, large, possibly chunk-encoded, messages. The interface is careful to never buffer entire requests or responses—the user is able to stream data.

HTTP message headers are represented by an 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.

`node.http.Server`

Event	Parameters	Notes
`"request"`	`request, response`	`request` is an instance of `node.http.ServerRequest` + `response` is an instance of `node.http.ServerResponse`
`"connection"`	`connection`	When a new TCP connection is established. `connection` is an object of type `node.http.Connection`. Usually users will not want to access this event. The `connection` can also be accessed at `request.connection`.
`"close"`	`errorno`	Emitted when the server closes. `errorno` is an integer which indicates what, if any, error caused the server to close. If no error occured `errorno` will be 0.

node.http.createServer(request_listener, options);: Returns a new web server object.

The options argument is optional. The options argument accepts the same values as the options argument for node.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.

`node.http.ServerRequest`

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
`"body"`	`chunk`	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 `request.setBodyEncoding()`.
`"complete"`		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 is undefined. 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.

`node.http.ServerResponse`

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 the encoding 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.

`node.http.Client`

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 and host 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 a ClientRequest object.

Do remember to include the Content-Length header if you plan on sending a body. If you plan on streaming the body, perhaps set Transfer-Encoding: chunked.

Note	the 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 with `request.sendBody()`.)

`node.http.ClientRequest`

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
`"response"`	`response`	Emitted when a response is received to this request. Typically the user will set a listener to this via the `request.finish()` method. + This event is emitted only once. + The `response` argument will be an instance of `node.http.ClientResponse`.

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 when chunk 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. The response_listener callback is executed with one argument which is an instance of node.http.ClientResponse.

`node.http.ClientResponse`

This object is created internally and passed to the "response" event.

Event	Parameters	Notes
`"body"`	`chunk`	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 `response.setBodyEncoding()`.
`"complete"`		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.

TCP

`node.tcp.Server`

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, {backlog: 1024});
server.listen(7000, "localhost");

Event	Parameters	Notes
`"connection"`	`connection`	Emitted when a new connection is made. `connection` is an instance of `node.tcp.Connection`.
`"close"`	`errorno`	Emitted when the server closes. `errorno` is an integer which indicates what, if any, error caused the server to close. If no error occured `errorno` will be 0.

node.tcp.createServer(connection_listener, options={});: Creates a new TCP server.

The connection_listener argument is automatically set as a listener for the "connection" event.

options for now only supports one option: backlog which should be an integer and describes how large of a connection backlog the operating system should maintain for this server. The backlog defaults to 1024.
server.listen(port, host=null): Tells the server to listen for TCP connections to port and host. Note, host is optional. If host is not specified the server will accept connections to any IP address on the specified port.
server.close(): Stops the server from accepting new connections.

`node.tcp.Connection`

This object is used as a TCP client and also as a server-side socket for node.tcp.Server.

Event	Parameters	Notes
`"connect"`		Call once the connection is established.
`"receive"`	`data`	Called when data is received on the connection. Encoding of data is set by `connection.setEncoding()`. `data` will either be a string, in the case of utf8, or an array of integer in the case of raw encoding.
`"eof"`		Called when the other end of the connection sends a FIN packet. After this is emitted the `readyState` will be `"writeOnly"`. One should probably just call `connection.close()` when this event is emitted.
`"disconnect"`	`had_error`	Emitted once the connection is fully disconnected. The argument `had_error` is a boolean which says if the connection was closed due to a transmission error. (TODO: access error codes.)

node.tcp.createConnection(port, host="127.0.0.1"): Creates a new connection object and opens a connection to the specified port and host. 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).

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api.txt

api.txt

NODE(1)

NAME

SYNOPSIS

DESCRIPTION

API

Helpers

Global Variables

Events

`node.EventEmitter`

`node.Promise`

Modules

`onLoad()`

`onExit()`

Timers

Child Processes

`node.Process`

File I/O

POSIX Wrappers

`node.fs.File`

HTTP

`node.http.Server`

`node.http.ServerRequest`

`node.http.ServerResponse`

`node.http.Client`

`node.http.ClientRequest`

`node.http.ClientResponse`

TCP

`node.tcp.Server`

`node.tcp.Connection`

Files

api.txt

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api.txt

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NODE(1)

NAME

SYNOPSIS

DESCRIPTION

API

Helpers

Global Variables

Events

node.EventEmitter

node.Promise

Modules

onLoad()

onExit()

Timers

Child Processes

node.Process

File I/O

POSIX Wrappers

node.fs.File

HTTP

node.http.Server

node.http.ServerRequest

node.http.ServerResponse

node.http.Client

node.http.ClientRequest

node.http.ClientResponse

TCP

node.tcp.Server

node.tcp.Connection

`node.EventEmitter`

`node.Promise`

`onLoad()`

`onExit()`

`node.Process`

`node.fs.File`

`node.http.Server`

`node.http.ServerRequest`

`node.http.ServerResponse`

`node.http.Client`

`node.http.ClientRequest`

`node.http.ClientResponse`

`node.tcp.Server`

`node.tcp.Connection`