node/doc/api.txt

NODE(1)
=======
Ryan Dahl <ry@tinyclouds.org>
Version, 0.1.18, 2009.11.17


== 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.

+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

[cols="1,2,10",options="header"]
|=========================================================
| 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 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: e.g. +{"rss":5828608,"vsize":3112529920}+

+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.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}+.

+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) {
  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 are instances of +process.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.

==== +process.EventEmitter+

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

[cols="1,2,10",options="header"]
|=========================================================
| 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) {
  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.

==== +process.Promise+

+process.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.

[cols="1,2,10",options="header"]
|=========================================================
| Event       | Parameters       | Notes
| +"success"+ | (depends)        |
| +"error"+   | (depends)        |
| +"cancel"+  | (depends)        |
|=========================================================

+promise.addCallback(listener)+ ::
Adds a listener for the +"success"+ event. Returns the same promise object.

+promise.addErrback(listener)+ ::
Adds a listener for the +"error"+ event. Returns the same promise object.

+promise.addCancelback(listener)+ ::
Adds a listener for the +"cancel"+ event. Returns the same promise object.

+promise.emitSuccess(arg1, arg2, ...)+ ::
If you created the promise (by doing +new process.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.

+promise.emitCancel(arg1, arg2, ...)+ ::
Emits the +"cancel"+ event. You may still get a +"success"+ or +"error"+
callback if the promise giver does not handle the cancel event. Use
+promise.cancel()+ to ignore any later events.

+promise.cancel()+ ::
Clears all +"success"+ and +"error"+ event listeners from the promise, then
emits the +"cancel"+ event. Whether or not the promise is actually canceled
or not depends on the promise giver. This also clears Promise.timeout() if one
was set.

+promise.timeout(timeout = undefined)+ ::
If the +timeout+ parameter is provided, the promise will emit an +"error"+
event after the given amount of millseconds. The timeout is canceled by any
+"success"+, +"error"+ or +"cancel"+ event being emitted by the Promise.
+
To tell apart a timeout 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.

[cols="1,2,10",options="header"]
|=========================================================
| 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 on to it and 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 cirlce of radius 4 is " + area(4));
----------------------------------------




=== Timers


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


+clearTimeout(timeoutId)+::
Prevents said timeout from triggering.


+setInterval(callback, delay)+::
To schedule the repeated execution of callback every +delay+ milliseconds. Returns
a +intervalId+ for possible use with +clearInterval()+.


+clearInterval(intervalId)+::
Stops a interval from triggering.


=== Child Processes

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

==== +process.ChildProcess+

[cols="1,2,10",options="header"]
|=========================================================
| 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=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) {
  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
(+process.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) {
  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": "*/*"
}
----------------------------------------

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+

[cols="1,2,10",options="header"]
|=========================================================
|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+ does.
+
The +request_listener+ is a function which is automatically
added to the +"request"+ event.

+server.listen(port, hostname)+ ::
Begin accepting connections on the specified port and hostname.
If the hostname is omitted, the server will accept connections
directed to any address. 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.

[cols="1,2,10",options="header"]
|=========================================================
|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.uri+ ::
Request URI Object. This contains only the parameters that are
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.uri+ will be
+
----------------------------------------
{ full: "/status?name=ryan",
  path: "/status",
  queryString: "name=ryan",
  params: { "name": "ryan" },
  fragment: ""
}
----------------------------------------


+request.headers+ ::
Read only.


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


+request.setBodyEncoding(encoding)+ ::
Set the encoding for the request body. Either +"utf8"+ or +"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.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.get(path, request_headers)+, +client.head(path, request_headers)+, +client.post(path, request_headers)+, +client.del(path, request_headers)+, +client.put(path, request_headers)+ ::

Issues a request; if necessary establishes connection. Returns a +http.ClientRequest+ instance.
+
+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()+.)


==== +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.

[cols="1,2,10",options="header"]
|=========================================================
|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&mdash;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 receieved,
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) {
    puts("BODY: " + chunk);
  });
});

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




==== +http.ClientResponse+

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

[cols="1,2,10",options="header"]
|=========================================================
|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 a
                "data" key.
  - on error: no parameters.

==== +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 name = part.headers["Content-Disposition"].name;
  var buffer = "";

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

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

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


[cols="1,2,10",options="header"]
|=========================================================
|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.
|=========================================================

==== +multipart.Part+

[cols="1,2,10",options="header"]
|=========================================================
|Event           | Parameters   | Notes
|+"body"+        | +chunk+      | Emitted when a chunk of body is read.
|+"complete"+    |              | Emitted when the end of the part is reached.
|=========================================================


=== 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");
----------------------------------------


[cols="1,2,10",options="header"]
|=========================================================
|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.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+.

[cols="1,2,10",options="header"]
|=========================================================
|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.

=== DNS module

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

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

-------------------------------------------------------------------------
var dns = require("dns");

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

resolution.addCallback(function (addresses, ttl, cname) {
  puts("addresses: " + JSON.stringify(addresses));
  puts("ttl: " + JSON.stringify(ttl));
  puts("cname: " + JSON.stringify(cname));

  for (var i = 0; i < addresses.length; i++) {
    var a = addresses[i];
    var reversing = dns.reverse(a);
    reversing.addCallback( function (domains, ttl, cname) {
      puts("reverse for " + a + ": " + JSON.stringify(domains));
    });
    reversing.addErrback( function (code, msg) {
      puts("reverse for " + a + " failed: " + msg);
    });
  }
});

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


+dns.resolve4(domain)+::

Resolves a domain (e.g. +"google.com"+) into an array of IPv4 addresses (e.g.
+["74.125.79.104", "74.125.79.105", "74.125.79.106"]+).
This function returns a promise.
- on success: returns +addresses, ttl, cname+. +ttl+ (time-to-live) is an integer
  specifying the number of seconds this result is valid for. +cname+ is the
  canonical name for the query.
- on error: returns +code, msg+. +code+ is one of the error codes listed
  below and +msg+ is a string describing the error in English.

+dns.resolve6(domain)+::

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

+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.



== 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> ");
------------------------------------



== 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 http:/cvs.schmorp.de/libev/ev.html[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 http://code.google.com/p/waf/[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
http://github.com/ry/node_postgres[node_postgres] for a real example.

// vim: set syntax=asciidoc: