node/website/api.txt

NODE(1)
=======
Ryan Dahl <ry@tinyclouds.org>
Version, 0.1.7, 2009.08.27


== Name

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



== Synopsis

An example of a web server written with Node which responds with "Hello
World" after waiting two seconds:

----------------------------------------
node.http.createServer(function (request, response) {
  setTimeout(function () {
    response.sendHeader(200, {"Content-Type": "text/plain"});
    response.sendBody("Hello World");
    response.finish();
  }, 2000);
}).listen(8000);
puts("Server running at http://127.0.0.1:8000/");
----------------------------------------

To run the server, put the code into a file called +example.js+ and execute
it with the node program

----------------------------------------
> node example.js
Server running at http://127.0.0.1:8000/
----------------------------------------



== API

Node supports 3 byte-string encodings: ASCII (+"ascii"+), UTF-8 (+"utf8"+),
and raw binary (+"raw"+).  It uses strings to represent ASCII and UTF-8
encoded data. For the moment, arrays of integers are used to represent raw
binary data--this representation is rather inefficient. This will
change in the future, when
http://code.google.com/p/v8/issues/detail?id=270[V8 supports Blob objects].

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


=== Helpers

+puts(string)+::
Outputs the +string+ and a trailing new-line to +stdout+.
+
Everything in node is asynchronous; +puts()+ is no exception. This might
seem ridiculous but, if for example, one is piping +stdout+ into an NFS
file, +printf()+ will block from network latency.  There is an internal
queue for +puts()+ output, so you can be assured that output will be
displayed in the order it was called.


+node.debug(string)+::
A synchronous output function. Will block the process and
output the string immediately to stdout.


+p(object)+ ::
Print the JSON representation of +object+ to the standard output.


+print(string)+::
Like +puts()+ but without the trailing new-line.


+node.exit(code)+::
Immediately ends the process with the specified code.

+node.cwd()+::
Returns the current working directory of the process.


=== Global Variables



+ARGV+ ::
An array containing the command line arguments.


+__filename+ ::
The filename of the script being executed.

+process+ ::
A special global object. The +process+ object is like the +window+ object of
browser-side javascript.


=== Events

Many objects in Node emit events: a TCP server emits an event each time
there is a connection, a child process emits an event when it exits. All
objects which emit events are are instances of +node.EventEmitter+.

Events are represented by a snakecased string. Here are some examples:
+"connection"+, +"receive"+, +"message_begin"+.

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

Some asynchronous file operations return an +EventEmitter+ called a
_promise_.  A promise emits just a single event when the operation is
complete.

==== +node.EventEmitter+

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.listeners(event)+ ::
Returns an array of listeners for the specified event. This array can be
manipulated, e.g. to remove listeners.

+emitter.emit(event, args)+ ::
Execute each of the listeners in order with the array +args+ as arguments.

==== +node.Promise+

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

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


=== Standard I/O

Standard I/O is handled through a special object +node.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 either an array of integers
                            (raw encoding) or a string (ascii or utf8
                            encoding). This event will only be emited after
                            +node.stdio.open()+ has been called.
| +"close"+  |            | Made when stdin has been closed.
|=========================================================

+node.stdio.open(encoding="utf8")+::
Open stdin. The program will not exit until +node.stdio.close()+ has been
called or the +"close"+ event has been emitted.

+node.stdio.write(data)+::
Write data to stdout.

+node.stdio.writeError(data)+::
Write data to stderr. Synchronous.

+node.stdio.close()+::
Close stdin.


=== Modules

Node has a simple module loading system.  In Node, files and modules are in
one-to-one correspondence.  As an example, +foo.js+ loads the module
+circle.js+.

The contents of +foo.js+:

----------------------------------------
var circle = require("circle.js");
puts("The area of a cirlce of radius 4 is " + circle.area(4));
----------------------------------------

The contents of +circle.js+:

----------------------------------------
var PI = 3.14;

exports.area = function (r) {
  return PI * r * r;
};

exports.circumference = function (r) {
  return 2 * PI * r;
};
----------------------------------------

The module +circle.js+ has exported the functions +area()+ and
+circumference()+.  To export an object, add to the special +exports+
object.  (Alternatively, one can use +this+ instead of +exports+.) Variables
local to the module will be private. In this example the variable +PI+ is
private to +circle.js+.

The module path is relative to the file calling +require()+.  That is,
+circle.js+ must be in the same directory as +foo.js+ for +require()+ to
find it.

HTTP URLs can also be used to load modules. For example,

----------------------------------------
var circle = require("http://tinyclouds.org/node/circle.js");
----------------------------------------

Like +require()+ the function +include()+ also loads a module. Instead of
returning a namespace object, +include()+ will add the module's exports into
the global namespace. For example:

----------------------------------------
include("circle.js");
puts("The area of a cirlce of radius 4 is " + area(4));
----------------------------------------

Functions +require_async()+ and +include_async()+ also exist.


==== +process.addListener("exit", function () { })+

When the program exits a special object called +process+ will emit an
+"exit"+ event.

The +"exit"+ event cannot perform I/O since the process is going to
forcably exit in less than microsecond. However, it is a good hook to
perform constant time checks of the module's state. E.G. for unit tests:

----------------------------------------
include("asserts.js");

var timer_executed = false;

setTimeout(function () {
  timer_executed = true
}, 1000);

process.addListener("exit", function () {
  assertTrue(timer_executed);
});
----------------------------------------

Just to reiterate: the +"exit"+ event, is not the place to close files or
shutdown servers. The process will exit before they get performed.



=== Timers


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


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


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


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


=== Child Processes

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

==== +node.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
triggered. +data+ is a string. At the moment all data passed to +stdout+ is
interrpreted as UTF-8 encoded.
+
If the child process closes its +stdout+ stream (a common thing to do on
exit), this event will be emitted with +data === null+.


|+"error"+  | +data+   |
Identical to the +"output"+ event except for +stderr+ instead of +stdout+.

|+"exit"+   | +code+   |
This event is emitted after the child process ends. +code+ is the final exit
code of the process. One can be assured that after this event is emitted
that the +"output"+ and +"error"+ callbacks will no longer be made.

|=========================================================

+node.createChildProcess(command)+::
Launches a new process with the given +command+. For example:
+
----------------------------------------
var ls = node.createChildProcess("ls -lh /usr");
ls.addListener("output", function (data) {
  puts(data);
});
----------------------------------------


+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 +"raw"+.


+child.close()+ ::
Closes the process's +stdin+ stream.


+child.kill(signal=node.SIGTERM)+ ::
Send a single to the child process.  If no argument is given, the process
will be sent +node.SIGTERM+.  The standard POSIX signals are defined under
the +node+ namespace (+node.SIGINT+, +node.SIGUSR1+, ...).



=== File I/O

File I/O is provided by simple wrappers around standard POSIX functions.
All POSIX wrappers have a similar form.
They return a promise (+node.Promise+). Example:

------------------------------------------------------------------------------
var promise = node.fs.unlink("/tmp/hello");
promise.addCallback(function () {
  puts("successfully deleted /tmp/hello");
});
------------------------------------------------------------------------------

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

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

It could be that +stat()+ is executed before the +rename()+.
The correct way to do this is to chain the promises.

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

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

------------------------------------------------------------------------------
node.fs.rename("/tmp/hello", "/tmp/world").wait();
node.fs.stat("/tmp/world").addCallback(function (stats) {
  puts("stats: " + JSON.stringify(stats));
});
------------------------------------------------------------------------------

+node.fs.rename(path1, path2)+ ::
  See rename(2).
  - on success: no parameters.
  - on error: no parameters.



+node.fs.stat(path)+ ::
  See stat(2).
  - on success: Returns +stats+ object. It looks like this:
    +{ dev: 2049, ino: 305352, mode: 16877, nlink: 12, uid: 1000, gid: 1000,
    rdev: 0, size: 4096, blksize: 4096, blocks: 8, atime:
    "2009-06-29T11:11:55Z", mtime: "2009-06-29T11:11:40Z", ctime:
    "2009-06-29T11:11:40Z" }+
  - on error: no parameters.

+node.fs.unlink(path)+ ::
  See unlink(2)
  - on success: no parameters.
  - on error: no parameters.


+node.fs.rmdir(path)+ ::
  See rmdir(2)
  - on success: no parameters.
  - on error: no parameters.


+node.fs.close(fd)+ ::
  See close(2)
  - on success: no parameters.
  - on error: no parameters.


+node.fs.open(path, flags, mode)+::
  See open(2). The constants like +O_CREAT+ are defined at +node.O_CREAT+.
  - on success: +fd+ is given as the parameter.
  - on error: no parameters.


+node.fs.write(fd, data, position)+::
  Write data to the file specified by +fd+. +data+ is either an array of
  integers (for raw data) or a string for UTF-8 encoded characters.
  +position+ refers to the offset from the beginning of the file where this
  data should be written. If +position+ is +null+, the data will be written at
  the current position. See pwrite(2).
  - on success: returns an integer +written+ which specifies how many _bytes_ were written.
  - on error: no parameters.


+node.fs.read(fd, length, position, encoding)+::

Read data from the file specified by +fd+.
+
+length+ is an integer specifying the number of
bytes to read.
+
+position+ is an integer specifying where to begin
reading from in the file.
+
+encoding+ is either +node.UTF8+
or +node.RAW+.
+
- on success: returns +data, bytes_read+, what was read from the file.
- on error: no parameters.

+node.fs.cat(filename, encoding)+::

Outputs the entire contents of a file. Example:
+
--------------------------------
node.fs.cat("/etc/passwd", "utf8").addCallback(function (content) {
  puts(content);
});
--------------------------------
+
- on success: returns +data+, what was read from the file.
- on error: no parameters.


=== 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.  That means, for example, that Node
does not, and will never, provide API to access or manipulate Cookies or
multi-part bodies.  _This is left to the user._


==== +node.http.Server+

[cols="1,2,10",options="header"]
|=========================================================
|Event           | Parameters   | Notes

|+"request"+     | +request, response+ |
+request+ is an instance of +node.http.ServerRequest+
+
+response+ is an instance of +node.http.ServerResponse+

|+"connection"+  | +connection+ |
When a new TCP connection is established.
+connection+ is an object of type +node.http.Connection+. Usually users will not
want to access this event. The +connection+ can also be accessed at
+request.connection+.

|+"close"+       | +errorno+    | Emitted when the server closes. +errorno+
                                  is an integer which indicates what, if any,
                                  error caused the server to close. If no
                                  error occured +errorno+ will be 0.

|=========================================================

+node.http.createServer(request_listener, options);+ ::
Returns a new web server object.
+
The +options+ argument is optional. The
+options+ argument accepts the same values as the
options argument for +node.tcp.Server+ does.
+
The +request_listener+ is a function which is automatically
added to the +"request"+ event.

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

+server.close()+ ::
Stops the server from accepting new connections.



==== +node.http.ServerRequest+

This object is created internally by a HTTP server--not by
the user--and passed as the first argument to a +"request"+ listener.

[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 either a String in the case of UTF-8 encoding or
an array of numbers in the case of raw encoding.  The body encoding is set
with +request.setBodyEncoding()+.

|+"complete"+    |        |
Emitted exactly once for each message. No arguments.
After emitted no other events will be emitted on the request.

|=========================================================

+request.method+ ::
The request method as a string. Read only. Example:
+"GET"+, +"DELETE"+.


+request.uri+ ::
Request URI Object. This contains only the parameters that are
present in the actual http request. That is, if the request is
+
----------------------------------------
GET /status?name=ryan HTTP/1.1\r\n
Accept: */*\r\n
\r\n
----------------------------------------
+
Then +request.uri+ will be
+
----------------------------------------
{ path: "/status",
  file: "status",
  directory: "/",
  params: { "name" : "ryan" }
}
----------------------------------------
+
In particular, note that +request.uri.protocol+ is
+undefined+. This is because there was no URI protocol given
in the actual HTTP Request.
+
+request.uri.anchor+, +request.uri.query+, +request.uri.file+, +request.uri.directory+, +request.uri.path+, +request.uri.relative+, +request.uri.port+, +request.uri.host+, +request.uri.password+, +request.uri.user+, +request.uri.authority+, +request.uri.protocol+, +request.uri.params+, +request.uri.toString()+, +request.uri.source+


+request.headers+ ::
Read only.


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


+request.setBodyEncoding(encoding)+ ::
Set the encoding for the request body. Either +"utf8"+ or +"raw"+. Defaults
to raw.


+request.pause()+ ::
Pauses request from emitting events.  Useful to throttle back an upload.


+request.resume()+ ::
Resumes a paused request.


+request.connection+ ::
The +node.http.Connection+ object.


==== +node.http.ServerResponse+

This object is created internally by a HTTP server--not by the user. It is
passed as the second parameter to the +"request"+ event.

+response.sendHeader(statusCode, headers)+ ::

Sends a response header to the request. The status code is a 3-digit HTTP
status code, like +404+. The second argument, +headers+ 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.


+response.finish()+ ::
This method signals to the server that all of the response headers and body
has been sent; that server should consider this message complete.
The method, +response.finish()+, MUST be called on each
response.



==== +node.http.Client+

An HTTP client is constructed with a server address as its
argument, the returned handle is then used to issue one or more
requests.  Depending on the server connected to, the client might
pipeline the requests or reestablish the connection after each
connection. _Currently the implementation does not pipeline requests._

Example of connecting to +google.com+

----------------------------------------
var google = node.http.createClient(80, "google.com");
var request = google.get("/");
request.finish(function (response) {
  puts("STATUS: " + response.statusCode);
  puts("HEADERS: " + JSON.stringify(response.headers));
  response.setBodyEncoding("utf8");
  response.addListener("body", function (chunk) {
    puts("BODY: " + chunk);
  });
});
----------------------------------------

+node.http.createClient(port, host)+ ::

Constructs a new HTTP client. +port+ and
+host+ refer to the server to be connected to. A
connection is not established until a request is issued.

+client.get(path, request_headers)+, +client.head(path, request_headers)+, +client.post(path, request_headers)+, +client.del(path, request_headers)+, +client.put(path, request_headers)+ ::

Issues a request; if necessary establishes connection. Returns a +node.http.ClientRequest+ instance.
+
+request_headers+ is optional.
Additional request headers might be added internally
by Node. Returns a +ClientRequest+ object.
+
Do remember to include the +Content-Length+ header if you
plan on sending a body. If you plan on streaming the body, perhaps
set +Transfer-Encoding: chunked+.
+
NOTE: the request is not complete. This method only sends
the header of the request. One needs to call
+request.finish()+ to finalize the request and retrieve
the response.  (This sounds convoluted but it provides a chance
for the user to stream a body to the server with
+request.sendBody()+.)


==== +node.http.ClientRequest+

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

[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 +node.http.ClientResponse+.
|=========================================================


+request.sendBody(chunk, encoding="ascii")+ ::

Sends a sucessive peice of the body.  By calling this method
many times, the user can stream a request body to a
server&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(response_listener)+ ::

Finishes sending the request. If any parts of the body are
unsent, it will flush them to the socket. If the request is
chunked, this will send the terminating +"0\r\n\r\n"+.
+
The parameter +response_listener+ is a callback which
will be executed when the response headers have been received.
The +response_listener+ callback is executed with one
argument which is an instance of +node.http.ClientResponse+.



==== +node.http.ClientResponse+

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

[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 either a String in the case of UTF-8 encoding or
an array of numbers in the case of raw encoding.  The body encoding is set
with +response.setBodyEncoding()+.

|+"complete"+    |        |
Emitted exactly once for each message. No arguments.
After emitted no other events will be emitted on the response.

|=========================================================

+response.statusCode+ ::
  The 3-digit HTTP response status code. E.G. +404+.

+response.httpVersion+ ::
  The HTTP version of the connected-to server. Probably either
  +"1.1"+ or +"1.0"+.

+response.headers+ ::
  The response headers.

+response.setBodyEncoding(encoding)+ ::
  Set the encoding for the response body. Either +"utf8"+ or +"raw"+.
  Defaults to raw.

+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 +node.http.Client+ that this response belongs to.



=== TCP

==== +node.tcp.Server+

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

----------------------------------------
function echo (socket) {
  socket.setEncoding("utf8");
  socket.addListener("connect", function () {
    socket.send("hello\r\n");
  });
  socket.addListener("receive", function (data) {
    socket.send(data);
  });
  socket.addListener("eof", function () {
    socket.send("goodbye\r\n");
    socket.close();
  });
}
var server = node.tcp.createServer(echo);
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 +node.tcp.Connection+.
|+"close"+       | +errorno+    | Emitted when the server closes. +errorno+
                                  is an integer which indicates what, if any,
                                  error caused the server to close. If no
                                  error occured +errorno+ will be 0.
|=========================================================

+node.tcp.createServer(connection_listener);+ ::
Creates a new TCP server.
+
The +connection_listener+ argument is automatically set as a listener for
the +"connection"+ event.


+server.listen(port, host=null, backlog=1024)+ ::
Tells the server to listen for TCP connections to +port+ 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 1024.  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.


==== +node.tcp.Connection+

This object is used as a TCP client and also as a server-side
socket for +node.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.  Encoding of data is set
                                  by +connection.setEncoding()+.  +data+
                                  will either be a string, in the case of
                                  utf8, or an array of integer in the case
                                  of raw encoding.
|+"eof"+         |              | Called when the other end of the
                                  connection sends a FIN packet.
                                  After this is emitted the +readyState+
                                  will be +"writeOnly"+. One should probably
                                  just call +connection.close()+ when this
                                  event is emitted.
|+"timeout"+     |              | Emitted if the connection times out from
                                  inactivity. The +"close"+ event will be 
                                  emitted immediately following this event. 
|+"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.)
|=========================================================

+node.tcp.createConnection(port, host="127.0.0.1")+::
Creates a new connection object and opens a connection to the specified
+port+ and +host+. If the second parameter is omitted, localhost is assumed.
+
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 +"utf8"+ or +"raw"+) for data that is received.

+connection.send(data, encoding="ascii")+::
Sends data on the connection. The data should be eithre an array
of integers (for raw binary) or a string (for utf8 or ascii).
The second parameter specifies the encoding in the case of a
string--it defaults to ASCII because encoding to UTF8 is
rather slow.


+connection.close()+::
Half-closes the connection. I.E. sends a FIN packet. It is
possible the server will still send some data. After calling
this +readyState+ will be +"readOnly"+.


+connection.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 inacitivty on
the connection. By default all +node.tcp.Connection+ objects have a timeout
of 60 seconds (60000 ms).
+
If +timeout+ is 0, then the idle timeout is disabled.


=== DNS

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

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

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

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

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


+node.dns.resolve4(domain)+::

Resolves a domain (e.g. +"google.com"+) into an array of IPv4 addresses (e.g.
+["74.125.79.104", "74.125.79.105", "74.125.79.106"]+).
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.

+node.dns.resolve6(domain)+::

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

+node.dns.reverse(ip)+::

Reverse resolves an ip address to an array of domain names.

- on success: returns +domains, ttl, cname+. +ttl+ (time-to-live) is an integer
  specifying the number of seconds this result is valid for. +cname+ is the
  canonical name for the query. +domains+ is an array of domains.
- on error: returns +code, msg+. +code+ is one of the error codes listed
  below and +msg+ is a string describing the error in English.


Each DNS query can return an error code.

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


// vim: set syntax=asciidoc: