NODE(1)

NAME

node - evented I/O for V8 JavaScript

SYNOPSIS

An example of a web server written with Node which responds with "Hello World":

var sys = require("sys"),
   http = require("http");
http.createServer(function (request, response) {
  response.writeHead(200, {"Content-Type": "text/plain"});
  response.write("Hello World\n");
  response.close();
}).listen(8000);
sys.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/

Encodings

Node supports 3 string encodings. UTF-8 ("utf8"), ASCII ("ascii"), and Binary ("binary"). "ascii" and "binary" only look at the first 8 bits of the 16bit JavaScript string characters. Both are relatively fast—use them if you can. "utf8" is slower and should be avoided when possible.

Global Objects

global: The global namespace object.
process: The process object. Most stuff lives in here. See the "process object" section.
require(): See the modules section.
require.paths: The search path for absolute path arguments to require().
__filename: The filename of the script being executed.
__dirname: The dirname of the script being executed.
module: A reference to the current module (of type process.Module). In particular module.exports is the same as the exports object. See src/process.js for more information.

The `process` Object

Event	Parameters	Notes
`"exit"`	`code`	Made when the process exits. A listener on this event should not try to perform I/O since the process will forcibly exit in less than a microsecond. However, it is a good hook to perform constant time checks of the module’s state (like for unit tests). The parameter `code` is the integer exit code passed to `process.exit()`.
`"uncaughtException"`	`exception`	Emitted when an exception bubbles all the way down to the event loop. If a listener is added for this exception, the default action (which is to print a stack trace and exit) will not occur.
`"SIGINT"`, `"SIGUSR1"`, …	(none)	Emitted when the processes receives a signal. See sigaction(2) for a list of standard POSIX signal names such as SIGINT, SIGUSR1, etc.

process.argv

An array containing the command line arguments.

process.env

An object containing the user environment. See environ(7).

process.pid

The PID of the process.

process.platform

What platform you’re running on. "linux2", "darwin", etc.

process.memoryUsage()

Returns the memory usage of the Node process. It looks like this

{ rss: 4935680
, vsize: 41893888
, heapTotal: 1826816
, heapUsed: 650472
}

heapTotal and heapUsed refer to V8’s memory usage.

process.nextTick(callback)

On the next loop around the event loop call this callback. This is not a simple alias to setTimeout(fn, 0), it’s much more efficient.

process.exit(code=0)

Ends the process with the specified code. By default it exits with the success code 0.

process.cwd()

Returns the current working directory of the process.

process.getuid(), process.setuid(id)

Gets/sets the user identity of the process. (See setuid(2).)

process.getgid(), process.setgid(id)

Gets/sets the group identity of the process. (See setgid(2).)

process.chdir(directory)

Changes the current working directory of the process.

process.umask([mask])

Sets or read the process’s file mode creation mask. Child processes inherit the mask from the parent process.

returns the old mask if mask argument is given, otherwise returns the current mask.

process.kill(pid, signal="SIGTERM")

Send a signal to a process. pid is the process id and signal is the signal to send; for example, "SIGINT" or "SIGUSR1". See kill(2) for more information.

process.compile(code, scriptOrigin)

Similar to eval() except that you can specify a scriptOrigin for better error reporting and the code cannot see the local scope.

System module

These function are in the module "sys". Use require("sys") to access them.

puts(string)

Outputs string and a trailing new-line to stdout.

print(string)

Like puts() but without the trailing new-line.

debug(string)

A synchronous output function. Will block the process and output string immediately to stdout.

log(string)

Output with timestamp.

inspect(object, showHidden, depth)

Return a string representation of object. (For debugging.)

If showHidden is true, then the object’s non-enumerable properties will be shown too.

If depth is provided, it tells inspect how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. The default is to only recurse twice. To make it recurse indefinitely, pass in null for depth.

exec(command, callback)

Executes the command as a child process, buffers the output and returns it in a callback.

var sys = require("sys");
sys.exec("ls /", function (err, stdout, stderr) {
  if (err) throw err;
  sys.puts(stdout);
});

The callback gets the arguments (err, stdout, stderr). On success err will be null. On error err will be an instance of Error and err.code will be the exit code of the child process.

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 instances of events.EventEmitter.

Events are represented by a camel-cased string. Here are some examples: "connection", "data", "messageBegin".

Functions can be then be attached to objects, to be executed when an event is emitted. These functions are called listeners.

`events.EventEmitter`

require("events") to access the events module.

All EventEmitters emit the event "newListener" when new listeners are added.

Event	Parameters	Notes
`"newListener"`	`event, listener`	This event is made any time someone adds a new listener.

emitter.addListener(event, listener)

Adds a listener to the end of the listeners array for the specified event.

server.addListener("connection", function (socket) {
  sys.puts("someone connected!");
});

emitter.removeListener(event, listener)

Remove a listener from the listener array for the specified event. Caution: changes array indices in the listener array behind the listener.

emitter.removeAllListeners(event)

Removes all listeners from the listener array for the specified event.

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, arg1, arg2, …)

Execute each of the listeners in order with the supplied arguments.

Standard I/O

Standard I/O is handled through a special object process.stdio. stdout and stdin are fully non-blocking (even when piping to files). stderr is synchronous.

Event	Parameters	Notes
`"data"`	`data`	Made when stdin has received a chunk of data. Depending on the encoding that stdin was opened with, `data` will be a string. This event will only be emited after `process.stdio.open()` has been called.
`"close"`		Made when stdin has been closed.

process.stdio.open(encoding="utf8"): Open stdin. The program will not exit until process.stdio.close() has been called or the "close" event has been emitted.
process.stdio.write(data): Write data to stdout.
process.stdio.writeError(data): Write data to stderr. Synchronous.
process.stdio.close(): Close stdin.

Modules

Node uses the CommonJS module system.

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 in the same directory.

The contents of foo.js:

var circle = require("./circle"),
var sys = require("sys");
sys.puts( "The area of a circle 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 function puts() comes from the module "sys", which is a built-in module. Modules which are not prefixed by "./" are built-in module—more about this later.

A module prefixed with "./" is relative to the file calling require(). That is, circle.js must be in the same directory as foo.js for require("./circle") to find it.

Without the leading "./", like require("mjsunit") the module is searched for in the require.paths array. require.paths on my system looks like this:

[ "/home/ryan/.node_libraries"
, "/usr/local/lib/node/libraries"
]

That is, when require("mjsunit") is called Node looks for

"/home/ryan/.node_libraries/mjsunit.js"
"/home/ryan/.node_libraries/mjsunit.node"
"/home/ryan/.node_libraries/mjsunit/index.js"
"/home/ryan/.node_libraries/mjsunit/index.node"
"/usr/local/lib/node/libraries/mjsunit.js"
"/usr/local/lib/node/libraries/mjsunit.node"
"/usr/local/lib/node/libraries/mjsunit/index.js"
"/usr/local/lib/node/libraries/mjsunit/index.node"

interrupting once a file is found. Files ending in ".node" are binary Addon Modules; see the section below about addons. "index.js" allows one to package a module as a directory.

require.paths can be modified at runtime by simply unshifting new paths onto it, or at startup with the NODE_PATH environmental variable (which should be a list of paths, colon separated).

Use process.mixin() to include modules into the global namespace.

process.mixin(GLOBAL, require("./circle"), require("sys"));
puts("The area of a circle of radius 4 is " + area(4));

Timers

The following are global variables

setTimeout(callback, delay, [arg, …]): To schedule execution of callback after delay milliseconds. Returns a timeoutId for possible use with clearTimeout().

Optionally, you can also pass arguments to the callback.
clearTimeout(timeoutId): Prevents said timeout from triggering.
setInterval(callback, delay, [arg, …]): To schedule the repeated execution of callback every delay milliseconds. Returns a intervalId for possible use with clearInterval().

Optionally, you can also pass arguments to the callback.
clearInterval(intervalId): Stops a interval from triggering.

Child Processes

Node provides a tridirectional popen(3) facility through the class process.ChildProcess. It is possible to stream data through the child’s stdin, stdout, and stderr in a fully non-blocking way.

`process.ChildProcess`

Event	Parameters	Notes
`"output"`	`data`	Each time the child process sends data to its `stdout`, this event is emitted. `data` is a string. 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.

process.createChildProcess(command, args=[], env=process.env)

Launches a new process with the given command, command line arguments, and environmental variables. For example:

var ls = process.createChildProcess("ls", ["-lh", "/usr"]);
ls.addListener("output", function (data) {
  sys.puts(data);
});

Note, if you just want to buffer the output of a command and return it, then exec() in /sys.js might be better.

child.pid

The PID of the child process.

child.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 "binary".

child.close()

Closes the process’s stdin stream.

child.kill(signal="SIGTERM")

Send a signal to the child process. If no argument is given, the process will be sent "SIGTERM". See signal(7) for a list of available signals.

File System

File I/O is provided by simple wrappers around standard POSIX functions. To use this module do require("fs"). All the methods have asynchornous and synchronous forms.

The asynchronous form always take a completion callback as its last argument. The arguments passed to the completion callback depend on the method, but the first argument is always reserved for an exception. If the operation was completed successfully, then the first argument will be null or undefined.

Here is an example of the asynchornous version:

var fs = require("fs"),
    sys = require("sys");

fs.unlink("/tmp/hello", function (err) {
  if (err) throw err;
  sys.puts("successfully deleted /tmp/hello");
});

Here is the synchronous version:

var fs = require("fs"),
    sys = require("sys");

fs.unlinkSync("/tmp/hello")
sys.puts("successfully deleted /tmp/hello");

With the asynchronous methods there is no guaranteed ordering. So the following is prone to error:

fs.rename("/tmp/hello", "/tmp/world", function (err) {
  if (err) throw err;
  sys.puts("renamed complete");
});
fs.stat("/tmp/world", function (err, stats) {
  if (err) throw err;
  sys.puts("stats: " + JSON.stringify(stats));
});

It could be that fs.stat is executed before fs.rename. The correct way to do this is to chain the callbacks.

fs.rename("/tmp/hello", "/tmp/world", function (err) {
  if (err) throw err;
  fs.stat("/tmp/world", function (err, stats) {
    if (err) throw err;
    sys.puts("stats: " + JSON.stringify(stats));
  });
});

In busy processes, the programmer is strongly encouraged to use the asynchronous versions of these calls. The synchronous versions will block the entire process until they complete—halting all connections.

fs.rename(path1, path2, callback)

Asynchronous rename(2). No arguments other than a possible exception are given to the completion callback.

fs.renameSync(path1, path2)

Synchronous rename(2).

fs.truncate(fd, len, callback)

Asynchronous ftruncate(2). No arguments other than a possible exception are given to the completion callback.

fs.truncateSync(fd, len)

Synchronous ftruncate(2).

fs.chmod(path, mode, callback)

Asynchronous chmod(2). No arguments other than a possible exception are given to the completion callback.

fs.chmodSync(path, mode)

Synchronous chmod(2).

fs.stat(path, callback)

fs.lstat(path, callback)

Asynchronous stat(2) or lstat(2). The callback gets two arguments (err, stats) where stats is a fs.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"
}

See the fs.Stats section below for more information.

fs.statSync(path)

fs.lstatSync(path)

Synchronous stat(2) or lstat(2). Returns an instance of fs.Stats.

fs.link(srcpath, dstpath, callback)

Asynchronous link(2). No arguments other than a possible exception are given to the completion callback.

fs.linkSync(dstpath, srcpath)

Synchronous link(2).

fs.symlink(linkdata, path, callback)

Asynchronous symlink(2). No arguments other than a possible exception are given to the completion callback.

fs.symlinkSync(linkdata, path)

Synchronous symlink(2).

fs.readlink(path, callback)

Asynchronous readlink(2). The callback gets two arguments (err, resolvedPath).

fs.readlinkSync(path)

Synchronous readlink(2). Returns the resolved path.

fs.realpath(path, callback)

Asynchronous realpath(2). The callback gets two arguments (err, resolvedPath).

fs.realpathSync(path)

Synchronous realpath(2). Returns the resolved path.

fs.unlink(path, callback)

Asynchronous unlink(2). No arguments other than a possible exception are given to the completion callback.

fs.unlinkSync(path)

Synchronous unlink(2).

fs.rmdir(path, callback)

Asynchronous rmdir(2). No arguments other than a possible exception are given to the completion callback.

fs.rmdirSync(path)

Synchronous rmdir(2).

fs.mkdir(path, mode, callback)

Asynchronous mkdir(2). No arguments other than a possible exception are given to the completion callback.

fs.mkdirSync(path, mode)

Synchronous mkdir(2).

fs.readdir(path, callback)

Asynchronous readdir(3). Reads the contents of a directory. The callback gets two arguments (err, files) where files is an array of the names of the files in the directory excluding "." and "..".

fs.readdirSync(path)

Synchronous readdir(3). Returns an array of filenames excluding "." and "..".

fs.close(fd, callback)

Asynchronous close(2). No arguments other than a possible exception are given to the completion callback.

fs.closeSync(fd)

Synchronous close(2).

fs.open(path, flags, mode, callback)

Asynchronous file open. See open(2). Flags can be "r", "r+", "w", "w+", "a", or "a+". The callback gets two arguments (err, fd).

fs.openSync(path, flags, mode)

Synchronous open(2).

fs.write(fd, data, position, encoding, callback)

Write data to the file specified by fd. 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).

The callback will be given two arguments (err, written) where written specifies how many bytes were written.

fs.writeSync(fd, data, position, encoding)

Synchronous version of fs.write(). Returns the number of bytes written.

fs.read(fd, length, position, encoding, callback)

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.

The callback is given three arguments, (err, data, bytesRead) where data is a string—what was read—and bytesRead is the number of bytes read.

fs.readSync(fd, length, position, encoding)

Synchronous version of fs.read. Returns an array [data, bytesRead].

fs.readFile(filename, encoding="utf8", callback)

Asynchronously reads the entire contents of a file. Example:

fs.readFile("/etc/passwd", function (err, data) {
  if (err) throw err;
  sys.puts(content);
});

The callback is passed two arguments (err, data), where data is the contents of the file.

fs.readFileSync(filename, encoding="utf8")

Synchronous version of fs.readFile. Returns the contents of the filename.

fs.writeFile(filename, data, encoding="utf8", callback)

Asynchronously writes data to a file. Example:

fs.writeFile("message.txt", "Hello Node", function (err) {
  if (err) throw err;
  sys.puts("It's saved!");
});

fs.writeFileSync(filename, data, encoding="utf8")

The synchronous version of fs.writeFile.

fs.watchFile(filename, [options,] listener)

Watch for changes on filename. The callback listener will be called each time the file changes.

The second argument is optional. The options if provided should be an object containing two members a boolean, persistent, and interval, a polling value in milliseconds. The default is {persistent: true, interval: 0}.

The listener gets two arguments the current stat object and the previous stat object:

fs.watchFile(f, function (curr, prev) {
  sys.puts("the current mtime is: " + curr.mtime);
  sys.puts("the previous mtime was: " + prev.mtime);
});

These stat objects are instances of fs.Stat.

fs.unwatchFile(filename)

Stop watching for changes on filename.

`fs.Stats`

Objects returned from fs.stat() and fs.lstat() are of this type.

stats.isFile()
stats.isDirectory()
stats.isBlockDevice()
stats.isCharacterDevice()
stats.isSymbolicLink()
stats.isFIFO()
stats.isSocket(): …

`fs.FileReadStream`

Event	Parameters	Notes
`"open"`	`fd`	The file descriptor was opened.
`"data"`	`chunk`	A chunk of data was read.
`"error"`	`err`	An error occured. This stops the stream.
`"end"`		The end of the file was reached.
`"close"`		The file descriptor was closed.

fs.createReadStream(path, [options]);

Returns a new FileReadStream object.

options is an object with the following defaults:

{ "flags": "r"
, "encoding": "binary"
, "mode": 0666
, "bufferSize": 4 * 1024
}

readStream.readable

A boolean that is true by default, but turns false after an "error" occured, the stream came to an "end", or forceClose() was called.

readStream.pause()

Stops the stream from reading further data. No "data" event will be fired until the stream is resumed.

readStream.resume()

Resumes the stream. Together with pause() this useful to throttle reading.

readStream.forceClose([callback])

Allows to close the stream before the "end" is reached. No more events other than "close" will be fired after this method has been called.

`fs.FileWriteStream`

Event	Parameters	Notes
`"open"`	`fd`	The file descriptor was opened.
`"drain"`		No more data needs to be written.
`"error"`	`err`	An error occured. This stops the stream.
`"close"`		The file descriptor was closed.

fs.createWriteStream(path, [options]);

Returns a new FileWriteStream object.

options is an object with the following defaults:

{ "flags": "w"
, "encoding": "binary"
, "mode": 0666
}

writeStream.writeable

A boolean that is true by default, but turns false after an "error" occured or close() / forceClose() was called.

writeStream.write(data, [callback])

Returns true if the data was flushed to the kernel, and false if it was queued up for being written later. A "drain" will fire after all queued data has been written.

You can also specify callback to be notified when the data from this write has been flushed. The first param is err, the second is bytesWritten.

writeStream.close([callback])

Closes the stream right after all queued write() calls have finished.

writeStream.forceClose([callback])

Allows to close the stream regardless of its current state.

HTTP

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

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

HTTP message headers are represented by an object like this:

{ "content-length": "123"
, "content-type": "text/plain"
, "connection": "keep-alive"
, "accept": "*/*"
}

Keys are lowercased. Values are not modified.

In order to support the full spectrum of possible HTTP applications, Node’s HTTP API is very low-level. It deals with 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.

`http.Server`

Event	Parameters	Notes
`"request"`	`request, response`	`request` is an instance of `http.ServerRequest` `response` is an instance of `http.ServerResponse`
`"connection"`	`connection`	When a new TCP connection is established. `connection` is an object of type `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.

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 tcp.Server.

The request_listener is a function which is automatically added to the "request" event.
server.setSecure(format_type, ca_certs, crl_list, private_key, certificate): Enable TLS for all incoming connections, with the specified credentials.

format_type currently has to be "X509_PEM", and each of the ca, crl, key and cert parameters are in the format of PEM strings.

ca_certs is a string that holds a number of CA certificates for use in accepting client connections that authenticate themselves with a client certificate. private_key is a PEM string of the unencrypted key for the server.
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. This function is synchronous.
server.close(): Stops the server from accepting new connections.

`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
`"data"`	`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 a string. The body encoding is set with `request.setBodyEncoding()`.
`"end"`	(none)	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.url

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

GET /status?name=ryan HTTP/1.1\r\n
Accept: text/plain\r\n
\r\n

Then request.url will be:

"/status?name=ryan"

If you would like to parse the URL into its parts, you can use require("url").parse(request.url). Example:

node> require("url").parse("/status?name=ryan")
{ href: '/status?name=ryan'
, search: '?name=ryan'
, query: 'name=ryan'
, pathname: '/status'
}

If you would like to extract the params from the query string, you can use the require("querystring").parse function, or pass true as the second argument to require("url").parse. Example:

node> require("url").parse("/status?name=ryan", true)
{ href: '/status?name=ryan'
, search: '?name=ryan'
, query: { name: 'ryan' }
, pathname: '/status'
}

request.headers

Read only.

request.httpVersion

The HTTP protocol version as a string. Read only. Examples: "1.1", "1.0"

request.setBodyEncoding(encoding="binary")

Set the encoding for the request body. Either "utf8" or "binary". Defaults to "binary".

request.pause()

Pauses request from emitting events. Useful to throttle back an upload.

request.resume()

Resumes a paused request.

request.connection

The http.Connection object.

`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.writeHead(statusCode[, reasonPhrase] , headers)

Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers. Optionally one can give a human-readable reasonPhrase as the second argument.

Example:

var body = "hello world";
response.writeHead(200, {
  "Content-Length": body.length,
  "Content-Type": "text/plain"
});

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

response.write(chunk, encoding="ascii")

This method must be called after writeHead 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.

The first time response.write() is called, it will send the buffered header information and the first body to the client. The second time response.write() is called, Node assumes you’re going to be streaming data, and sends that seperately. That is, the response is buffered up to the first chunk of body.

response.close()

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.close(), MUST be called on each response.

`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 sys = require("sys"),
   http = require("http");
var google = http.createClient(80, "www.google.com");
var request = google.request("GET", "/", {"host": "www.google.com"});
request.addListener('response', function (response) {
  sys.puts("STATUS: " + response.statusCode);
  sys.puts("HEADERS: " + JSON.stringify(response.headers));
  response.setBodyEncoding("utf8");
  response.addListener("data", function (chunk) {
    sys.puts("BODY: " + chunk);
  });
});
request.close();

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.request([method], path, [request_headers]): Issues a request; if necessary establishes connection. Returns a http.ClientRequest instance.

+ method is optional and defaults to "GET" if omitted.

+ request_headers is optional. 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.close() 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.write().)

client.setSecure(format_type, ca_certs, crl_list, private_key, certificate): Enable TLS for the client connection, with the specified credentials.

format_type currently has to be "X509_PEM", and each of the ca, crl, key and cert parameters are in the format of PEM strings, and optional.

ca_certs is a string that holds a number of CA certificates for use in deciding the authenticity of the remote server. private_key is a PEM string of the unencrypted key for the client, which together with the certificate allows the client to authenticate itself to the server.

`http.ClientRequest`

This object is created internally and returned from the request methods of a http.Client. It represents an in-progress request whose header has already been sent.

To get the response, add a listener for response to the request object. response will be emitted from the request object when the response headers have been received. The response event is executed with one argument which is an instance of http.ClientResponse.

During the response event, one can add listeners to the response object; particularly to listen for the "data" event. Note that the response event is called before any part of the response body is received, so there is no need to worry about racing to catch the first part of the body. As long as a listener for +data is added during the +response event, the entire body will be caught.

// Good
request.addListener('response', function (response) {
  response.addListener("data", function (chunk) {
    sys.puts("BODY: " + chunk);
  });
});

// Bad - misses all or part of the body
request.addListener('response', function (response) {
  setTimeout(function () {
    response.addListener("data", function (chunk) {
      sys.puts("BODY: " + chunk);
    });
  }, 10);
});

Event	Parameters	Notes
`"response"`	`response`	Emitted when a response is received to this request. This event is emitted only once. The `response` argument will be an instance of `http.ClientResponse`.

request.write(chunk, encoding="ascii"): Sends a chunk 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.close(): 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".

`http.ClientResponse`

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

Event	Parameters	Notes
`"data"`	`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 a String. The body encoding is set with `response.setBodyEncoding()`.
`"end"`		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.
response.setBodyEncoding(encoding): Set the encoding for the response body. Either "utf8" or "binary". Defaults to "binary".
response.pause(): Pauses response from emitting events. Useful to throttle back a download.
response.resume(): Resumes a paused response.
response.client: A reference to the http.Client that this response belongs to.

Multipart Parsing

A library to parse multipart internet messages is included with Node. To use it, require("multipart").

multipart.parse(message): Returns a multipart.Stream wrapper around a streaming message. The message must contain a headers member, and may be either an HTTP request object or a JSGI-style request object with either a forEachable or String body.
See the Stream class below.
multipart.cat(message, callback): On success, callback is called with (null, stream) where stream is a multipart.Stream object representing the completed message. The body of each part is saved on the body member.
On error, callback is called with (err) where err is an instanceof the Error object. This indicates that the message was malformed in some way.
Note: This function saves the entire message into memory. As such, it is ill-suited to parsing actual incoming messages from an HTTP request! If a user uploads a very large file, then it may cause serious problems. No checking is done to ensure that the file does not overload the memory. Only use multipart.cat with known and trusted input!

`multipart.Stream`

The multipart.Stream class is a streaming parser wrapped around a message. The Stream also contains the properties described for the part objects below, and is a reference to the top-level message.

Event	Parameters	Notes
`"partBegin"`	`part`	Emitted when a new part is found in the stream. `part` is a `part object`, described below.
`"partEnd"`	`part`	Emitted when a part is done.
`"body"`	`chunk`	Emitted when a chunk of the body is read.
`"complete"`		Emitted when the end of the stream is reached.
`"error"`	`error`	Emitted when a parse error is encountered. This indicates that the message is malformed.

stream.part: The current part being processed. This is important, for instance, when responding to the body event.
stream.isMultiPart: True if the stream is a multipart message. Generally this will be true, but non-multipart messages will behave the same as a multipart message with a single part, and isMultiPart will be set to false.
stream.parts: An array of the parts contained within the message. Each is a part object.
stream.pause: If the underlying message supports pause and resume, then this will pause the stream.
stream.resume: If the underlying message supports pause and resume, then this will resume the paused stream.

`multipart.Part`

As it parses the message, the Stream object will create Part objects.

part.parent: The message that contains this part.
part.headers: The headers object for this message.
part.filename: The filename, if specified in the content-disposition or content-type header. For uploads, downloads, and attachments, this is the intended filename for the attached file.
part.name: The name, if specified in the content-disposition or content-type header. For multipart/form-data messages, this is the name of the field that was posted, and the body specifies the value.
part.isMultiPart: True if this part is a multipart message.
part.parts: Array of children contained within a multipart message, or falsey.
part.boundary: For multipart messages, this is the boundary that separates subparts.
part.type: For multipart messages, this is the multipart type specified in the content-type header. For example, a message with content-type: multipart/form-data will have a type property of form-data.

Example

Here is an example for parsing a multipart/form-data request:

var multipart = require("multipart"),
  sys = require("sys"),
  http = require("http");
http.createServer(function (req, res) {
  var mp = multipart.parse(req),
    fields = {},
    name, filename;
  mp.addListener("error", function (er) {
    res.writeHead(400, {"content-type":"text/plain"});
    res.write("You sent a bad message!\n"+er.message);
    res.close();
  });
  mp.addListener("partBegin", function (part) {
    name = part.name;
    filename = part.filename;
    if (name) fields[name] = "";
  });
  mp.addListener("body", function (chunk) {
    if (name) {
      // just a demo.  in reality, you'd probably
      // want to sniff for base64 encoding, decode,
      // and write the bytes to a file or something.
      if (fields[name].length > 1024) return;
      fields[name] += chunk;
    }
  });
  mp.addListener("complete", function () {
    var response = "You posted: \n" + sys.inspect(fields);
    res.writeHead(200, {
      "content-type" : "text/plain",
      "content-length" : response.length
    });
    res.write(response);
    res.close();
  })
});

Nested Multipart Messages

Nested multipart parsing is supported. The stream.part object always refers to the current part. If part.isMultiPart is set, then that part is a multipart message, which contains other parts. You can inspect its parts array to see the list of sub-parts, which may also be multipart, and contain sub-parts.

TCP

To use the TCP server and client one must require("tcp").

`tcp.Server`

Here is an example of a echo server which listens for connections on port 7000:

var tcp = require("tcp");
var server = tcp.createServer(function (socket) {
  socket.setEncoding("utf8");
  socket.addListener("connect", function () {
    socket.write("hello\r\n");
  });
  socket.addListener("data", function (data) {
    socket.write(data);
  });
  socket.addListener("end", function () {
    socket.write("goodbye\r\n");
    socket.close();
  });
});
server.listen(7000, "localhost");

Event	Parameters	Notes
`"connection"`	`connection`	Emitted when a new connection is made. `connection` is an instance of `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 occurred `errorno` will be 0.

tcp.createServer(connection_listener);: Creates a new TCP server.

The connection_listener argument is automatically set as a listener for the "connection" event.
server.setSecure(format_type, ca_certs, crl_list, private_key, certificate): Enable TLS for all incoming connections, with the specified credentials.

format_type currently has to be "X509_PEM", and each of the ca, crl, key and cert parameters are in the format of PEM strings.

ca_certs is a string that holds a number of CA certificates for use in accepting client connections that authenticate themselves with a client certificate. private_key is a PEM string of the unencrypted key for the server.
server.listen(port, host=null, backlog=128): Tells the server to listen for TCP connections to port and host.

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 128. The backlog argument defines the maximum length to which the queue of pending connections for the server may grow.

This function is synchronous.
server.close(): Stops the server from accepting new connections. This function is asynchronous, the server is finally closed when the server emits a "close" event.

`tcp.Connection`

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

Event	Parameters	Notes
`"connect"`		Call once the connection is established after a call to `createConnection()` or `connect()`.
`"data"`	`data`	Called when data is received on the connection. `data` will be a string. Encoding of data is set by `connection.setEncoding()`.
`"end"`		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.
`"timeout"`		Emitted if the connection times out from inactivity. The `"close"` event will be emitted immediately following this event.
`"drain"`		Emitted when the write buffer becomes empty. Can be used to throttle uploads.
`"close"`	`had_error`	Emitted once the connection is fully closed. The argument `had_error` is a boolean which says if the connection was closed due to a transmission error. (TODO: access error codes.)

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.

When the connection is established the "connect" event will be emitted.
connection.connect(port, host="127.0.0.1"): Opens a connection to the specified port and host. createConnection() also opens a connection; normally this method is not needed. Use this only if a connection is closed and you want to reuse the object to connect to another server.

This function is asynchronous. When the "connect" event is emitted the connection is established. If there is a problem connecting, the "connect" event will not be emitted, the "close" event will be emitted with had_error == true.
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 "ascii", "utf8", or "binary") for data that is received.
connection.write(data, encoding="ascii"): Sends data on the connection. The second parameter specifies the encoding in the case of a string—it defaults to ASCII because encoding to UTF8 is rather slow.

Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory. drain will be emitted when the buffer is again free.
connection.close(): Half-closes the connection. I.E., it sends a FIN packet. It is possible the server will still send some data. After calling this readyState will be "readOnly".
connection.forceClose(): Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).
connection.pause(): Pauses the reading of data. That is, "data" events will not be emitted. Useful to throttle back an upload.
connection.resume(): Resumes reading after a call to pause().
connection.setTimeout(timeout): Sets the connection to timeout after timeout milliseconds of inactivity on the connection. By default all tcp.Connection objects have a timeout of 60 seconds (60000 ms).

If timeout is 0, then the idle timeout is disabled.
connection.setNoDelay(noDelay=true): Disables the Nagle algorithm. By default TCP connections use the Nagle algorithm, they buffer data before sending it off. Setting noDelay will immediately fire off data each time connection.write() is called.
connection.verifyPeer(): Returns an integer indicating the trusted status of the peer in a TLS connection.

Returns 1 if the peer’s certificate is issued by one of the trusted CAs, the certificate has not been revoked, is in the issued date range, and if the peer is the server, matches the hostname.

Returns 0 if no certificate was presented by the peer, or negative result if the verification fails (with a given reason code). This function is synchronous.
connection.getPeerCertificate(format): For a TLS connection, returns the peer’s certificate information, as defined by the given format.

A format of "DNstring" gives a single string with the combined Distinguished Name (DN) from the certificate, as comma delimited name=value pairs as defined in RFC2253. This function is synchronous.

DNS module

Use require("dns") to access this module.

Here is an example which resolves "www.google.com" then reverse resolves the IP addresses which are returned.

var dns = require("dns"),
    sys = require("sys");

dns.resolve4("www.google.com", function (err, addresses, ttl, cname) {
  if (err) throw err;

  sys.puts("addresses: " + JSON.stringify(addresses));
  sys.puts("ttl: " + JSON.stringify(ttl));
  sys.puts("cname: " + JSON.stringify(cname));

  for (var i = 0; i < addresses.length; i++) {
    var a = addresses[i];
    dns.reverse(a, function (err, domains, ttl, cname) {
      if (err) {
        puts("reverse for " + a + " failed: " + e.message);
      } else {
        sys.puts("reverse for " + a + ": " + JSON.stringify(domains));
      }
    });
  }
});

dns.resolve(domain, rrtype = A, callback): Resolves a domain (e.g. "google.com") into an array of the record types specified by rrtype. Valid rrtypes are A (IPV4 addresses), AAAA (IPV6 addresses), MX (mail exchange records), TXT (text records), SRV (SRV records), and PTR (used for reverse IP lookups).

The callback has arguments (err, 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. The type of each item in addresses is determined by the record type, and described in the documentation for the corresponding lookup methods below.

On error, err would be an instanceof Error object, where err.errno is one of the error codes listed below and err.message is a string describing the error in English.
dns.resolve4(domain, callback): The same as dns.resolve(), but only for IPv4 queries (A records). addresses is an array of IPv4 addresses (e.g. ["74.125.79.104", "74.125.79.105", "74.125.79.106"]).
dns.resolve6(domain, callback): The same as dns.resolve4() except for IPv6 queries (an AAAA query).
dns.resolveMx(domain, callback): The same as dns.resolve(), but only for mail exchange queries (MX records). addresses is an array of MX records, each with a priority and an exchange attribute (e.g. [{"priority": 10, "exchange": "mx.example.com"},…]).
dns.resolveTxt(domain, callback): The same as dns.resolve(), but only for text queries (TXT records). addresses is an array of the text records available for domain (e.g., ["v=spf1 ip4:0.0.0.0 ~all"]).
dns.resolveSrv(domain, callback): The same as dns.resolve(), but only for service records (SRV records). addresses is an array of the SRV records available for domain. Properties of SRV records are priority, weight, port, and name (e.g., [{"priority": 10, {"weight": 5, "port": 21223, "name": "service.example.com"}, …]).
dns.reverse(ip, callback): Reverse resolves an ip address to an array of domain names.

The callback has arguments (err, 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.

If there an an error, err will be non-null and an instanceof the Error object.

Each DNS query can return an error code.

dns.TEMPFAIL: timeout, SERVFAIL or similar.
dns.PROTOCOL: got garbled reply.
dns.NXDOMAIN: domain does not exists.
dns.NODATA: domain exists but no data of reqd type.
dns.NOMEM: out of memory while processing.
dns.BADQUERY: the query is malformed.

Assert Module

This module is used for writing unit tests for your applications, you can access it with require("assert").

assert.fail(actual, expected, message, operator): Tests if actual is equal to expected using the operator provided.
assert.ok(value, message): Tests if value is a true value, it is equivilant to assert.equal(true, value, message);
assert.equal(actual, expected, message): Tests shallow, coercive equality with the equal comparison operator ( == ).
assert.notEqual(actual, expected, message): Tests shallow, coercive non-equality with the not equal comparison operator ( != ).
assert.deepEqual(actual, expected, message): Tests for deep equality.
assert.notDeepEqual(actual, expected, message): Tests for any deep inequality.
assert.strictEqual(actual, expected, message): Tests strict equality, as determined by the strict equality operator ( === )
assert.notStrictEqual(actual, expected, message): Tests strict non-equality, as determined by the strict not equal operator ( !== )
assert.throws(block, error, message): Expects block to throw an error.
assert.doesNotThrow(block, error, message): Expects block not to throw an error.

Path Module

This module contains utilities for dealing with file paths. Use require("path") to use it. It provides the following methods:

path.join(/* path1, path2, … */)

Join all arguments together and resolve the resulting path. Example:

node> require("path").join("/foo", "bar", "baz/asdf", "quux", "..")
"/foo/bar/baz/asdf"

path.normalizeArray(arr)

Normalize an array of path parts, taking care of ".." and "." parts. Example:

path.normalizeArray(["",
  "foo", "bar", "baz", "asdf", "quux", ".."])
// returns
[ '', 'foo', 'bar', 'baz', 'asdf' ]

path.normalize(p)

Normalize a string path, taking care of ".." and "." parts. Example:

path.normalize("/foo/bar/baz/asdf/quux/..")
// returns
"/foo/bar/baz/asdf"

path.dirname(p)

Return the directory name of a path. Similar to the Unix dirname command. Example:

path.dirname("/foo/bar/baz/asdf/quux")
// returns
"/foo/bar/baz/asdf"

path.basename(p, ext)

Return the last portion of a path. Similar to the Unix basename command. Example:

path.basename("/foo/bar/baz/asdf/quux.html")
// returns
"quux.html"

path.basename("/foo/bar/baz/asdf/quux.html", ".html")
// returns
"quux"

path.extname(p)

Return the extension of the path. Everything after the last ., if there is no . then it returns an empty string. Examples:

path.extname("index.html")
// returns
".html"

path.extname("index")
// returns
""

path.exists(p, callback)

Test whether or not the given path exists. Then, call the callback argument with either true or false. Example:

path.exists("/etc/passwd", function (exists) {
  sys.debug(exists ? "it's there" : "no passwd!");
});

URL Module

This module has utilities for URL resolution and parsing.

Parsed URL objects have some or all of the following fields, depending on whether or not they exist in the URL string. Any parts that are not in the URL string will not be in the parsed object. Examples are shown for the URL "http://user:pass@host.com:8080/p/a/t/h?query=string#hash"

href: The full URL that was originally parsed. Example: "http://user:pass@host.com:8080/p/a/t/h?query=string#hash"
protocol: The request protocol. Example: "http:"
host: The full host portion of the URL, including port and authentication information. Example: "user:pass@host.com:8080"
auth: The authentication information portion of a URL. Example: "user:pass"
hostname: Just the hostname portion of the host. Example: "host.com"
port: The port number portion of the host. Example: "8080"
pathname: The path section of the URL, that comes after the host and before the query, including the initial slash if present. Example: "/p/a/t/h"
search: The "query string" portion of the URL, including the leading question mark. Example: "?query=string"
query: Either the "params" portion of the query string, or a querystring-parsed object. Example: "query=string" or {"query":"string"}
hash: The "fragment" portion of the URL including the pound-sign. Example: "#hash"

The following methods are provided by the URL module:

url.parse(urlStr, parseQueryString=false): Take a URL string, and return an object. Pass true as the second argument to also parse the query string using the querystring module.
url.format(urlObj): Take a parsed URL object, and return a formatted URL string.
url.resolve(from, to): Take a base URL, and a href URL, and resolve them as a browser would for an anchor tag.

Query String Module

This module provides utilities for dealing with query strings. It provides the following methods:

querystring.stringify(obj, sep="&", eq="=")

Serialize an object to a query string. Optionally override the default separator and assignment characters. Example:

querystring.stringify({foo: 'bar'})
// returns
"foo=bar"

querystring.parse(str, sep="&", eq="=")

Deserialize a query string to an object. Optionally override the default separator and assignment characters.

querystring.parse('a=b&b=c')
// returns
{ 'a': 'b'
, 'b': 'c'
}

querystring.escape

The escape function used by querystring.stringify, provided so that it could be overridden if necessary.

querystring.unescape

The unescape function used by querystring.parse, provided so that it could be overridden if necessary.

REPL

A Read-Eval-Print-Loop is available both as a standalone program and easily includable in other programs.

The standalone REPL is called node-repl and is installed at $PREFIX/bin/node-repl. It’s recommended to use it with the program rlwrap for a better user interface. I set

alias node-repl="rlwrap node-repl"

in my zsh configuration.

Inside the REPL, Control+D will exit. The special variable _ (underscore) contains the result of the last expression.

The library is called /repl.js and it can be used like this:

var sys = require("sys"),
    tcp = require("tcp"),
   repl = require("repl");
nconnections = 0;
tcp.createServer(function (c) {
  sys.error("Connection!");
  nconnections += 1;
  c.close();
}).listen(5000);
repl.start("simple tcp server> ");

The repl provides access to any variables in the global scope. You can expose a variable to the repl explicitly by assigning it to the repl.scope object:

var count = 5;
repl.start();
repl.scope.count = count;

Addons

Addons are dynamically linked shared objects. They can provide glue to C and C++ libraries. The API (at the moment) is rather complex, involving knowledge of several libraries:

V8 JavaScript, a C++ library. Used for interfacing with JavaScript: creating objects, calling functions, etc. Documented mostly in the v8.h header file (deps/v8/include/v8.h in the Node source tree).
libev, C event loop library. Anytime one needs to wait for a file descriptor to become readable, wait for a timer, or wait for a signal to received one will need to interface with libev. That is, if you perform any I/O, libev will need to be used. Node uses the EV_DEFAULT event loop. Documentation can be found here.
libeio, C thread pool library. Used to execute blocking POSIX system calls asynchronously. Mostly wrappers already exist for such calls, in src/file.cc so you will probably not need to use it. If you do need it, look at the header file deps/libeio/eio.h.
Internal Node libraries. Most importantly is the node::EventEmitter class which you will likely want to derive from.
Others. Look in deps/ for what else is available.

Node statically compiles all its dependencies into the executable. When compiling your module, you don’t need to worry about linking to any of these libraries.

To get started let’s make a small Addon which does the following except in C++:

exports.hello = "world";

To get started we create a file hello.cc:

#include <v8.h>

using namespace v8;

extern "C" void
init (Handle<Object> target)
{
  HandleScope scope;
  target->Set(String::New("hello"), String::New("World"));
}

This source code needs to be built into hello.node, the binary Addon. To do this we create a file called wscript which is python code and looks like this:

srcdir = "."
blddir = "build"
VERSION = "0.0.1"

def set_options(opt):
  opt.tool_options("compiler_cxx")

def configure(conf):
  conf.check_tool("compiler_cxx")
  conf.check_tool("node_addon")

def build(bld):
  obj = bld.new_task_gen("cxx", "shlib", "node_addon")
  obj.target = "hello"
  obj.source = "hello.cc"

Running node-waf configure build will create a file build/default/hello.node which is our Addon.

node-waf is just WAF, the python-based build system. node-waf is provided for the ease of users.

All Node addons must export a function called init with this signature:

extern "C" void init (Handle<Object> target)

For the moment, that is all the documentation on addons. Please see node_postgres for a real example.