plugin XEP-0353, XEP-0234, jingle: WebRTC data channel signaling implementation: Implement XEP-0343: Signaling WebRTC Data Channels in Jingle. The current version of the XEP (0.3.1) has no implementation and contains some flaws. After discussing this on xsf@, Daniel (from Conversations) mentioned that they had a sprint with Larma (from Dino) to work on another version and provided me with this link: https://gist.github.com/iNPUTmice/6c56f3e948cca517c5fb129016d99e74 . I have used it for my implementation. This implementation reuses work done on Jingle A/V call (notably XEP-0176 and XEP-0167 plugins), with adaptations. When used, XEP-0234 will not handle the file itself as it normally does. This is because WebRTC has several implementations (browser for web interface, GStreamer for others), and file/data must be handled directly by the frontend. This is particularly important for web frontends, as the file is not sent from the backend but from the end-user's browser device. Among the changes, there are: - XEP-0343 implementation. - `file_send` bridge method now use serialised dict as output. - New `BaseTransportHandler.is_usable` method which get content data and returns a boolean (default to `True`) to tell if this transport can actually be used in this context (when we are initiator). Used in webRTC case to see if call data are available. - Support of `application` media type, and everything necessary to handle data channels. - Better confirmation message, with file name, size and description when available. - When file is accepted in preflight, it is specified in following `action_new` signal for actual file transfer. This way, frontend can avoid the display or 2 confirmation messages. - XEP-0166: when not specified, default `content` name is now its index number instead of a UUID. This follows the behaviour of browsers. - XEP-0353: better handling of events such as call taken by another device. - various other updates. rel 441

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ping: get response time of an XMPP entity
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``ping`` is more or less the equivalent of the command of the same name on most OSes, but
for XMPP. It send a `XEP-0199`_ PING and wait for the answer. When (and if) received, the
time to receive the answer is shown, else the time to receive the error message is shown.
This can be helpful to quickly test the connection with the server or a device.

If you need to get only the response time (without text around), you may use ``-d,
--delay-only``.

.. _XEP-0199: https://xmpp.org/extensions/xep-0199.html

example
-------

Get reponse time of a server::

  $ li ping example.org