Communication
*************

Sending HTTP requests and receiving responses is an important feature of almost
every application running in the browser. Most commonly, the technique used is
termed Ajax. qooxdoo's communication stack offers many ways to facilitate HTTP
communication at different levels of abstraction.

.. _pages/communication#low_level_requests:

Low-level requests
==================

At the very core, HTTP requests from the browser are made by interfacing with
the HTTP client API or by adding a script tag to the document. Classes dealing
with those low-level transport methods can be found in the ``qx.bom.request``
namespace. Usually they are not instantiated directly by the user.

``Xhr`` is a wrapper of the HTTP client API offered by the browser. It's
purpose is to hide inconsistencies and to work around bugs found in popular
implementations. The interface of ``qx.bom.request.Xhr`` is similar to
`XMLHttpRequest <http://www.w3.org/TR/XMLHttpRequest2/>`_, the HTTP client API
specified by the W3C.

``Script`` is a script loader. Internally, the class deals with adding and
removing script tags to the document and keeping track of the load status. Just
like ``qx.bom.request.Xhr``, the interface is modeled based on XMLHttpRequest.

``Jsonp`` builds on the script loader and adds functionality needed to receive
JSONP responses. JSONP stands for JSON with padding and is a technique to
safely receive remote data. It's main advantage compared to to ``Xhr`` is that
cross-origin requests are supported in all browsers.

Higher-level requests
=====================

Classes found in ``qx.io.request`` build on the groundwork laid by
``qx.bom.request``. Properties allow to conveniently setup a request and
fine-grained events facilitate handling changes of the request's status or
response.

.. toctree::

  communication/request_io

Note that historically, qooxdoo comes with two transport layers. The old
transport layer is described below.

.. toctree::

   communication/remote_io


REST
=============

``qx.io.rest.Resource`` is a client-side wrapper of a REST resource.

.. toctree::

  communication/rest

Remote Procedure Calls (RPC)
=========================================

.. toctree::

   communication/rpc

RPC Servers
-----------

.. toctree::

   communication/rpc_server_writer_guide

Specific Widget Communication
=============================

.. toctree::

   widget/table_remote_model

Development & Testing
=====================

.. toctree::

  communication/fake_server