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*             HTTPClient            *

  HTTPClient is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  HTTPClient is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  GNU General Public License for more details.
  You should have received a copy of the GNU General Public License
  along with HTTPClient.  If not, see <http://www.gnu.org/licenses/>.
* Creating a HTTP Client

HTTP Client works with the Arduino Ethernet Library. Before you can create
a HTTP client you must initialize your ethernet connection with something 

  Ethernet.begin(mac, ip);

For details on this see http://arduino.cc/en/Reference/ServerBegin

To create a client (in this example for pachube) you can simply call one of 
the constructors:

    //  The address of the server you want to connect to (pachube.com):
    byte server[] = { 173,203,98,29 }; 
    HTTPClient client("api.pachube.com",server);

which is equivalent to

    HTTPClient client("api.pachube.com",server,80);

Now you are ready to go.

* Posting request

HTTP client supports three types of requests
- normal GET request to get some data from a URL
- POST requests to transfer bigger amount of data to a server
- PUT request as sepcified by REST APIs
- currently there is no need for DELETE requests - so they do not exist yet.

The result of a request is a stream (aka FILE*) by that you can read the data
without the need to keep the whole answer in memory - which would fail for most
HTML pages.
FILE* streams are a bit more unusual the normal Arduino streams. They have been 
choosen since you can use all the nice fprintff and fscanf routines of avr-libc.
After reading the response from the stream it has to be closed with the method
DO NOT FORGET IT. Each stream has some data attached and if you forget to close the 
stream you get a memory leak, slowly filling up the precious memory of the Arduino.

The result code of a HTTP request can be read with getLastReturnCode(). It returns a 
integer containing the return code.  200 indicates that everything was ok.
For further details refer to http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

The HTTPClient has also a debug mode which can be witched on and off by using debug()
with parameter 0 as no debug and anything else Ð e.g. -1 Ð as enabling debug output.
By default the debug code is disabled. If debug is enabled the complete request and 
response is printed out on the serial connection. 
Very useful if your request do not work.

All request take a number of parameters (depending on the request type):

- the URI - a string (char*) containing the uri - which is normally everything 
  following the hostname of a URL for http://arduino.cc/en/Reference/HomePage
  it would be Reference/HomePage
- optional parameters as key value pairs. Parameters are appended to a URL like
  parameters are values of the struct http_client_parameter. It is easiest to
  do this like
      http_client_parameter parameters[] = {
        { "key","afad32216dd2aa83c768ce51eef041d69a90a6737b2187dada3bb301e4c48841" }
        ,{ NULL,NULL }
- for POST and PUT request a string with additional data can be passed as a string. The data
  has to be in memory. Future Versions may have future features.
- for all requests additional headers can be specified. It works exactly the same was as uri
    http_client_parameter pachube_api_header[] = {
      { "X-PachubeApiKey","afad32216dd2aa83c768ce51eef041d69a90a6737b2187dada3bb301e4c48841" }
      ,{ NULL,NULL }
Even though the HTTPClient supports HTTP 1.1 request no keep alive requests are supported currently.

*** Contributions ****

Thanks to colagrosso http://github.com/colagrosso for fixing the URL encoding
Thanks to hex705 http://github.com/hex705 for properly porting it to Arduino 1.0