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182 lines
6 KiB
ReStructuredText
182 lines
6 KiB
ReStructuredText
Send/Receive IQ Stanzas
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=======================
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Unlike :class:`~sleekxmpp.stanza.message.Message` and
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:class:`~sleekxmpp.stanza.presence.Presence` stanzas which only use
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text data for basic usage, :class:`~sleekxmpp.stanza.iq.Iq` stanzas
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require using XML payloads, and generally entail creating a new
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SleekXMPP plugin to provide the necessary convenience methods to
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make working with them easier.
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Basic Use
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---------
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XMPP's use of :class:`~sleekxmpp.stanza.iq.Iq` stanzas is built around
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namespaced ``<query />`` elements. For clients, just sending the
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empty ``<query />`` element will suffice for retrieving information. For
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example, a very basic implementation of service discovery would just
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need to be able to send:
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.. code-block:: xml
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<iq to="user@example.com" type="get" id="1">
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<query xmlns="http://jabber.org/protocol/disco#info" />
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</iq>
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Creating Iq Stanzas
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~~~~~~~~~~~~~~~~~~~
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SleekXMPP provides built-in support for creating basic :class:`~sleekxmpp.stanza.iq.Iq`
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stanzas this way. The relevant methods are:
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq`
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq_get`
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq_set`
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq_result`
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq_error`
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* :meth:`~sleekxmpp.basexmpp.BaseXMPP.make_iq_query`
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These methods all follow the same pattern: create or modify an existing
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:class:`~sleekxmpp.stanza.iq.Iq` stanza, set the ``'type'`` value based
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on the method name, and finally add a ``<query />`` element with the given
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namespace. For example, to produce the query above, you would use:
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.. code-block:: python
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self.make_iq_get(queryxmlns='http://jabber.org/protocol/disco#info',
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ito='user@example.com')
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Sending Iq Stanzas
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~~~~~~~~~~~~~~~~~~
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Once an :class:`~sleekxmpp.stanza.iq.Iq` stanza is created, sending it
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over the wire is done using its :meth:`~sleekxmpp.stanza.iq.Iq.send()`
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method, like any other stanza object. However, there are a few extra
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options to control how to wait for the query's response.
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These options are:
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* ``block``: The default behaviour is that :meth:`~sleekxmpp.stanza.iq.Iq.send()`
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will block until a response is received and the response stanza will be the
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return value. Setting ``block`` to ``False`` will cause the call to return
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immediately. In which case, you will need to arrange some way to capture
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the response stanza if you need it.
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* ``timeout``: When using the blocking behaviour, the call will eventually
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timeout with an error. The default timeout is 30 seconds, but this may
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be overidden two ways. To change the timeout globally, set:
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.. code-block:: python
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self.response_timeout = 10
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To change the timeout for a single call, the ``timeout`` parameter works:
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.. code-block:: python
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iq.send(timeout=60)
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* ``callback``: When not using a blocking call, using the ``callback``
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argument is a simple way to register a handler that will execute
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whenever a response is finally received. Using this method, there
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is no timeout limit. In case you need to remove the callback, the
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name of the newly created callback is returned.
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.. code-block:: python
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cb_name = iq.send(callback=self.a_callback)
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# ... later if we need to cancel
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self.remove_handler(cb_name)
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Properly working with :class:`~sleekxmpp.stanza.iq.Iq` stanzas requires
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handling the intended, normal flow, error responses, and timed out
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requests. To make this easier, two exceptions may be thrown by
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:meth:`~sleekxmpp.stanza.iq.Iq.send()`: :exc:`~sleekxmpp.exceptions.IqError`
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and :exc:`~sleekxmpp.exceptions.IqTimeout`. These exceptions only
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apply to the default, blocking calls.
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.. code-block:: python
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try:
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resp = iq.send()
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# ... do stuff with expected Iq result
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except IqError as e:
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err_resp = e.iq
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# ... handle error case
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except IqTimeout:
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# ... no response received in time
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pass
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If you do not care to distinguish between errors and timeouts, then you
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can combine both cases with a generic :exc:`~sleekxmpp.exceptions.XMPPError`
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exception:
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.. code-block:: python
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try:
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resp = iq.send()
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except XMPPError:
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# ... Don't care about the response
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pass
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Advanced Use
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------------
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Going beyond the basics provided by SleekXMPP requires building at least a
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rudimentary SleekXMPP plugin to create a :term:`stanza object` for
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interfacting with the :class:`~sleekxmpp.stanza.iq.Iq` payload.
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.. seealso::
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* :ref:`create-plugin`
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* :ref:`work-with-stanzas`
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* :ref:`using-handlers-matchers`
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The typical way to respond to :class:`~sleekxmpp.stanza.iq.Iq` requests is
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to register stream handlers. As an example, suppose we create a stanza class
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named ``CustomXEP`` which uses the XML element ``<query xmlns="custom-xep" />``,
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and has a :attr:`~sleekxmpp.xmlstream.stanzabase.ElementBase.plugin_attrib` value
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of ``custom_xep``.
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There are two types of incoming :class:`~sleekxmpp.stanza.iq.Iq` requests:
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``get`` and ``set``. You can register a handler that will accept both and then
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filter by type as needed, as so:
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.. code-block:: python
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self.register_handler(Callback(
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'CustomXEP Handler',
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StanzaPath('iq/custom_xep'),
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self._handle_custom_iq))
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# ...
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def _handle_custom_iq(self, iq):
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if iq['type'] == 'get':
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# ...
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pass
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elif iq['type'] == 'set':
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# ...
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pass
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else:
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# ... This will capture error responses too
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pass
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If you want to filter out query types beforehand, you can adjust the matching
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filter by using ``@type=get`` or ``@type=set`` if you are using the recommended
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:class:`~sleekxmpp.xmlstream.matcher.stanzapath.StanzaPath` matcher.
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.. code-block:: python
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self.register_handler(Callback(
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'CustomXEP Handler',
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StanzaPath('iq@type=get/custom_xep'),
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self._handle_custom_iq_get))
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# ...
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def _handle_custom_iq_get(self, iq):
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assert(iq['type'] == 'get')
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