# NODE(1)

Ryan Dahl
`<ry@tinyclouds.org>`
version 0.1.27, 2010.02.03

## 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.sendHeader(200, {"Content-Type": "text/plain"});
      response.sendBody("Hello World\n");
      response.finish();
    }).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/

## API

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.

Unless otherwise noted, functions are all asynchronous and do not block execution.

### Global Objects

`global`

  The global namespace object.

`process`

  The process object. Most stuff lives in here. See the "process object" section.

`require(path)`

  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.

`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.chdir(directory)`

  Changes the current working directory of the process.

`process.umask(mask)`

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

  - returns the old 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.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:

      process.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 `posix.Stat`.

`process.unwatchFile(filename)`

  Stop watching for changes on `filename`.

`process.compile(source, scriptOrigin)`

  Just like `eval()` except that you can specify a `scriptOrigin` for better error reporting.

`process.mixin([deep], target, object1, [objectN])`

  Extend one object with one or more others, returning the modified object. If no target is specified, the `GLOBAL` namespace itself is extended. Keep in mind that the target object will be modified, and will be returned from `process.mixin()`.

  If a boolean true is specified as the first argument, Node performs a deep copy, recursively copying any objects it finds. Otherwise, the copy will share structure with the original object(s).

  Undefined properties are not copied. However, properties inherited from the object’s prototype will be copied over.

### System module

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

`puts(string)`

  Outputs the `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 the string immediately to stdout.

`inspect(object)`

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

`exec(command)`

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

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

  - on success: stdout buffer, stderr buffer

  - on error: exit code, stdout buffer, stderr buffer

### 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"`, `"receive"`, `"messageBegin"`.

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.

#### `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.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.

#### `events.Promise`

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

`events.Promise` inherits from `process.EventEmitter`. A promise emits one of two events: `"success"` or `"error"`. After emitting its event, it will not emit anymore events.

Event | Parameters | Notes
--- | --- | ---
`"success"` | (depends) |
`"error"` | (depends) |

`promise.addCallback(listener)`

  Adds a listener for the `"success"` event. Returns the same promise object. The listener is executed right away if the promise has already fired.

`promise.addErrback(listener)`

  Adds a listener for the `"error"` event. Returns the same promise object. The listener is executed right away if the promise has already fired.

`promise.emitSuccess(arg1, arg2, …)`

  If you created the promise (by doing `new events.Promise()`) then call `emitSuccess` to emit the `"success"` event with the given arguments.

  (`promise.emit("success", arg1, arg2, …)` should also work, but doesn’t at the moment due to a bug; use `emitSuccess` instead.)

`promise.emitError(arg1, arg2, …)`

  Emits the `"error"` event. If no error handler is attached to the promise between `promise.emitError()` and `process.nextTick()`, an exception is thrown.

  To explain the exception behavior, assume you have a "computeQuestion" function as follows:

      var events = require('events');
      function computeQuestion(answer) {
        var promise = new events.Promise();
        if (answer !== 42) {
          promise.emitError('wrong answer');
          return promise;
        }
        // compute the question for 42

        return promise;
      }

  You can stop an exception to be thrown here by attaching an errback handler right away (in the same event loop tick) like this:

      computeQuestion(23).addErrback(function() {
        // No exception will be thrown
      });

  However, if you try to attach the error handler in a later tick, the promise will already have thrown an exception:

      var promise = computeQuestion(23);
      setTimeout(function() {
        promise.addErrback(function() {
          // This will never execute, the promise already threw an exception
        });
      }, 1000);

`promise.timeout(timeout = undefined)`

  If the `timeout` parameter is provided, the promise will emit an `"error"` event after the given amount of milliseconds. The timeout is canceled by any `"success"` or `"error"` event being emitted by the promise.

  To tell a timeout apart from a regular "error" event, use the following test:

      promise.addErrback(function(e) {
        if (e instanceof Error && e.message === "timeout") {
          // handle timeout
        } else {
          // handle regular error
        }
      });

  If the `timeout` parameter is not provided, the current timeout value, if any, is returned.

`promise.wait()`

  Blocks futher execution until the promise emits a success or error event. Events setup before the call to `promise.wait()` was made may still be emitted and executed while `promise.wait()` is blocking.

  If there was a single argument to the `"success"` event then it is returned. If there were multiple arguments to `"success"` then they are returned as an array.

  If `"error"` was emitted instead, `wait()` throws an error.

  IMPORTANT `promise.wait()` is not a true fiber/coroutine. If any other promises are created and made to wait while the first promise waits, the first promise’s wait will not return until all others return. The benefit of this is a simple implementation and the event loop does not get blocked. Disadvantage is the possibility of situations where the promise stack grows infinitely large because promises keep getting created and keep being told to wait(). Use `promise.wait()` sparingly—probably best used only during program setup, not during busy server activity.

### 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

1. `"/home/ryan/.node_libraries/mjsunit.js"`

2. `"/home/ryan/.node_libraries/mjsunit.node"`

3. `"/home/ryan/.node_libraries/mjsunit/index.js"`

4. `"/home/ryan/.node_libraries/mjsunit/index.node"`

5. `"/usr/local/lib/node/libraries/mjsunit.js"`

6. `"/usr/local/lib/node/libraries/mjsunit.node"`

7. `"/usr/local/lib/node/libraries/mjsunit/index.js"`

8. `"/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

`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.

### POSIX module

File I/O is provided by simple wrappers around standard POSIX functions. To use this module do `require("posix")`.

All POSIX wrappers have a similar form. They return a promise (`events.Promise`). Example of deleting a file:

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

    var promise = posix.unlink("/tmp/hello");

    promise.addCallback(function () {
      sys.puts("successfully deleted /tmp/hello");
    });

There is no guaranteed ordering to the POSIX wrappers. The following is very much prone to error

    posix.rename("/tmp/hello", "/tmp/world");
    posix.stat("/tmp/world").addCallback(function (stats) {
      sys.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.

    posix.rename("/tmp/hello", "/tmp/world").addCallback(function () {
      posix.stat("/tmp/world").addCallback(function (stats) {
        sys.puts("stats: " + JSON.stringify(stats));
      });
    });

Or use the `promise.wait()` functionality:

    posix.rename("/tmp/hello", "/tmp/world").wait();
    var stats = posix.stat("/tmp/world").wait();
    sys.puts("stats: " + JSON.stringify(stats));

`posix.rename(path1, path2)`

  See rename(2).

  - on success: no parameters.

  - on error: no parameters.

`posix.stat(path)`

  See stat(2).

  - on success: Returns `posix.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 `posix.Stats` section below for more information.

  - on error: no parameters.

`posix.unlink(path)`

  See unlink(2)

  - on success: no parameters.

  - on error: no parameters.

`posix.rmdir(path)`

  See rmdir(2)

  - on success: no parameters.

  - on error: no parameters.

`posix.mkdir(path, mode)`

  See mkdir(2)

  - on success: no parameters.

  - on error: no parameters.

`posix.readdir(path)`

  Reads the contents of a directory.

  - on success: One argument, an array containing the names (strings) of the files in the directory (excluding "." and "..").

  - on error: no parameters.

`posix.close(fd)`

  See close(2)

  - on success: no parameters.

  - on error: no parameters.

`posix.open(path, flags, mode)`

  See open(2). The constants like `O_CREAT` are defined at `process.O_CREAT`.

  - on success: `fd` is given as the parameter.

  - on error: no parameters.

`posix.write(fd, data, position, encoding)`

  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).

  - on success: returns an integer `written` which specifies how many bytes were written.

  - on error: no parameters.

`posix.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.

  - on success: returns `data, bytes_read`, what was read from the file.

  - on error: no parameters.

`posix.cat(filename, encoding="utf8")`

  Outputs the entire contents of a file. Example:

      posix.cat("/etc/passwd").addCallback(function (content) {
        sys.puts(content);
      });

  - on success: returns `data`, what was read from the file.

  - on error: no parameters.

#### `posix.Stats`

Objects returned from `posix.stat()` are of this type.

`stats.isFile()`
`stats.isDirectory()`
`stats.isBlockDevice()`
`stats.isCharacterDevice()`
`stats.isSymbolicLink()`
`stats.isFIFO()`
`stats.isSocket()`

  …

### 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
--- | --- | ---
`"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 a string. The body encoding is set with `request.setBodyEncoding()`.
`"complete"` | (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.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`, are 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.

  The first time `sendBody` is called, it will send the buffered header information and the first body to the client. The second time `sendBody` 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.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.

#### `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.finish(function (response) {
      sys.puts("STATUS: " + response.statusCode);
      sys.puts("HEADERS: " + JSON.stringify(response.headers));
      response.setBodyEncoding("utf8");
      response.addListener("body", function (chunk) {
        sys.puts("BODY: " + chunk);
      });
    });

`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.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()`.)

`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.

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 `http.ClientResponse`.

`request.sendBody(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.finish(responseListener)`

  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 `responseListener` is a callback which will be executed when the response headers have been received. The `responseListener` callback is executed with one argument which is an instance of `http.ClientResponse`.

  In the `responseListener` callback, one can add more listeners to the response, in particular listening for the `"body"` event. Note that the `responseListener` is called before any part of the 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 `"body"` is added during the `responseListener` callback, the entire body will be caught.

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

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

#### `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 a String. 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.

`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 HTTP requests with `multipart/form-data` is included with Node. To use it, `require("multipart")`.

`multipart.parse(options)`

  - on success: Returns an object where each key holds the value of one part of the stream. `options` can either be an instance of `http.ServerRequest` or an object containing a "boundary" and an optional "data" key.

  - on error: Returns an instanceof Error object. Right now only the request content-type / boundary option is checked. The stream data itself is not validated.

#### `multipart.Stream`

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

    var multipart = require("multipart");
    var stream = new multipart.Stream(options);
    var parts = {};

    stream.addListener("part", function (part) {
      var buffer = "";

      part.addListener("body", function(chunk) {
        buffer = buffer + chunk;
      });

      part.addListener("complete", function() {
        parts[part.name] = buffer;
      });
    });

    stream.addListener("complete", function() {
      // The parts object now contains all parts and data
    });

Event | Parameters | Notes
--- | --- | ---
`"part"` | `part` | Emitted when a new part is found in the stream. `part` is an instance of `multipart.Part`.
`"complete"` |  | Emitted when the end of the stream is reached.

`stream.bytesTotal`

  The amount of bytes this stream is expected to have.

`stream.bytesReceived`

  The amount of bytes received by this stream so far.

#### `multipart.Part`

Event | Parameters | Notes
--- | --- | ---
`"body"` | `chunk` | Emitted when a chunk of body is read.
`"complete"` |  | Emitted when the end of the part is reached.

`part.name`

  The field name of this part.

`part.filename`

  The filename of this part. Only set for file uploads.

### 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.send("hello\r\n");
      });
      socket.addListener("receive", function (data) {
        socket.send(data);
      });
      socket.addListener("eof", function () {
        socket.send("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()`.
`"receive"` | `data` | Called when data is received on the connection. `data` will be a string. Encoding of data is set by `connection.setEncoding()`.
`"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.
`"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.send(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.

`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.readPause()`

  Pauses the reading of data. That is, `"receive"` events will not be emitted. Useful to throttle back an upload.

`connection.readResume()`

  Resumes reading if reading was paused by `readPause()`.

`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.send()` 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");

    var resolution = dns.resolve4("www.google.com");

    resolution.addCallback(function (addresses, ttl, cname) {
      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];
        var reversing = dns.reverse(a);
        reversing.addCallback( function (domains, ttl, cname) {
          sys.puts("reverse for " + a + ": " + JSON.stringify(domains));
        });
        reversing.addErrback( function (code, msg) {
          sys.puts("reverse for " + a + " failed: " + msg);
        });
      }
    });

    resolution.addErrback(function (code, msg) {
      sys.puts("error: " + msg);
    });

`dns.resolve(domain, rrtype = A)`

  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). 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. 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: returns `code, msg`. `code` is one of the error codes listed below and `msg` is a string describing the error in English.

`dns.resolve4(domain)`

  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)`

  The same as `dns.resolve4()` except for IPv6 queries (an `AAAA` query).

`dns.resolveMx(domain)`

  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)`

  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)`

  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)`

  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 and `msg` is a string describing the error in English.

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:

      node> require("path").normalizeArray(["", "foo", "bar", "baz", "asdf", "quux", ".."])
      [
        "",
        "foo",
        "bar",
        "baz",
        "asdf"
      ]

`path.normalize(p)`

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

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

`path.dirname(p)`

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

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

`path.basename(p, ext)`

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

      node> require("path").basename("/foo/bar/baz/asdf/quux.html")
      "quux.html"
      node> require("path").basename("/foo/bar/baz/asdf/quux.html", ".html")
      "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:

      node> require("path").extname("index.html")
      ".html"
      node> require("path").extname("index")
      ""

`path.exists(p, callback)`

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

      require("path").exists("/etc/passwd", function (exists) {
        require("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:

      node> require("querystring").stringify({foo:"bar", baz : {quux:"asdf", oof : "rab"}, boo:[1,2,3]})
      "foo=bar&baz%5Bquux%5D=asdf&baz%5Boof%5D=rab&boo%5B%5D=1&boo%5B%5D=2&boo%5B%5D=3"

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

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

      node> require("querystring").parse("foo=bar&baz%5Bquux%5D=asdf&baz%5Boof%5D=rab&boo%5B%5D=1")
      {
        "foo": "bar",
        "baz": {
          "quux": "asdf",
          "oof": "rab"
        },
        "boo": [
          1
        ]
      }

`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.