Communications
==============

Apart from moving around in the game world and talking, players might
need other forms of communication. This is offered by Evennia's ``Comm``
system. Stock evennia implements a 'MUX-like' system of channels, but
there is nothing stopping you from changing things to better suit your
taste.

Comms rely on two main database objects - ``Msg`` and ``Channel``.

Msg
---

The ``Msg`` object is the basic unit of communication in Evennia. A
message works a little like an e-mail; it always has a sender (a
`Player <Players.html>`_) and one or more recipients. The recipients may
be either other Players, or a *Channel* (see below). You can mix
recipients to send the message to both Channels and Players if you like.

Once created, a ``Msg`` is normally not changed. It is peristently saved
in the database. This allows for comprehensive logging of
communications, both in channels, but also for allowing
senders/receivers to have 'mailboxes' with the messages they want to
keep.

Properties defined on \`Msg\`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-  ``sender`` - this is a reference to a unique `Player <Players.html>`_
   object sending the message.
-  ``receivers`` - a list of target `Players <Players.html>`_ to send
   to.
-  ``channels`` - a list of target Channels to send to.
-  ``message`` - the actual text being sent
-  ``date_sent`` - when message was sent (auto-created).
-  ``locks`` - a `lock definition <Locks.html>`_.

You create new messages in code using ``ev.create_message`` (or
``src.utils.create.create_message.``)

!TempMsg
~~~~~~~~

``src.objects.models`` contains a class called ``TempMsg`` that mimics a
``Msg`` but does not get saved to the database and do not require a
sender object of a certain type. It's not used by default, but you could
use it in code to send one-off messages to systems expecting a ``Msg``.

Channels
--------

Channels act as generic distributors of messages. Players *subscribe* to
channels and can then send and receive message from it. Channels have
`Locks <Locks.html>`_ to limit who may join them.

There are three default channels created in stock Evennia - ``MUDinfo``,
``MUDconnections`` and ``Public``. Two first ones are server-related
messages meant for Admins, the last one is open to everyone to chat on
(all new players are automatically joined to it when logging in, useful
for asking questions). The default channels created are defined by
``settings.CHANNEL_PUBLIC``, ``settings.CHANNEL_MUDINFO`` and
``settings.CHANNEL_CONNECTINFO``.

You create new channels with ``ev.create_message`` (or
``src.utils.create.create_channel``).

In code, messages are sent to a channel using the
``msg(message, from_obj=None)`` method. The argument ``message`` can
either be a previously constructed ``Msg`` object or a message string.
If you send a text string, you should usually also define ``from_obj``;
a ``Msg`` object will then be created for you behind the scenes. If you
don't supply ``from_obj``, just the string will be sent to the channel
and nothing will be stored in the database (could be useful for certain
spammy error messages). You can also use ``channel.tempmsg()`` to always
send a non-persistent message, also if you send it a ``Msg`` object.

::

    # assume we have a 'sender' object and a channel named 'mychan'

    # send and store in database 
    from src.utils import create
    mymsg = create.create_message(sender, "Hello!", channels=[mychan])
    mychan.msg(mymsg)

    # send a one-time message
    mychan.msg("Hello!")

    # send a one-time message created from a Msg object
    mychan.tempmsg(mymsg)

As a more advanced note, sending text to channels is a "special
exception" as far as commands are concerned, and you may completely
customize how this works by defining a *system\_command* with your own
code. See `Commands <Commands.html>`_ for more details.

Properties defined on \`Channel\`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-  ``key`` - main name for channel
-  ``aliases`` - alternative native names for channels
-  ``desc`` - optional description of channel (seen in listings)
-  ``keep_log`` (bool) - if the channel should store messages (default)
-  ``locks`` - A `lock definition <Locks.html>`_. Channels normally use
   the access\_types ``send, admin`` and ``listen``.

External Connections
====================

Channels may also communicate through what is called an *External
Connection*. Whereas normal users send messages through in-game Evennia
commands, an external connection instead takes data from a remote
location. `IMC2 <IMC2.html>`_ and `IRC <IRC.html>`_ connections make use
of this.