Slave channels

Slave channel is more like a wrap over an API of IM, it encloses messages from the IM into appropriate objects and deliver it to the master channel.

Although we suggest that slave channel should match with an IM platform, but you may try to model it for anything that can deliver information as messages, and has a limited list of end-points to deliver messages to and from as chats.

In most of the cases, slave channels SHOULD be identified as one single user from the IM platform, instead of a bot. You should only use a bot for slave channels when:

  • the IM platform puts no difference between a user and a bot, or

  • bots on the IM platform can do exactly same things, if not more, as a user, and bots can be created easier than user account.

Additional features

Slave channels can offer more functions than what EFB requires, such as creating groups, search for friends, etc, via additional features.

Such features are accessed by the user in a CLI-like style. An “additional feature” method MUST only take one string parameter aside from self, and wrap it with extra() decorator. The extra decorator takes 2 arguments: name – a short name of the feature, and desc – a description of the feature with its usage.

desc SHOULD describe what the feature does and how to use it. It’s more like the help text for an CLI program. Since method of invoking the feature depends on the implementation of the master channel, you SHOULD use "{function_name}" as its name in desc, and master channel will replace it with respective name depend on their implementation.

The method MUST in the end return a string, which will be shown to the user as its result, or None to notify the master channel there will be further interaction happen. Depending on the functionality of the feature, it may be just a simple success message, or a long chunk of results.

The callable MUST NOT raise any exception to its caller. Any exceptions occurred within should be expected and processed.

Callable name of such methods has a more strict standard than a normal Python 3 identifier name, for compatibility reason. An additional feature callable name MUST:

  • be case sensitive

  • include only upper and lower-case letters, digits, and underscore.

  • does not start with a digit.

  • be in a length between 1 and 20 inclusive

  • be as short and concise as possible, but keep understandable

It can be expressed in a regular expression as:


An example is as follows:

       desc="Return back the same string from input.\n"
            "    {function_name} text")
def echo(self, arguments: str = "") -> str:
    return arguments

Message commands

Message commands are usually sent by slave channels so that users can respond to certain messages that has specific required actions.

Possible cases when message commands could be useful:

  • Add as friends when a contact card is received.

  • Accept or decline when a friend request is received.

  • Vote to a voting message.

A message can be attached with a list of commands, in which each of them has:

  • a human-friendly name,

  • a callable name,

  • a list of positional arguments (*args), and

  • a dict of keyword arguments (**kwargs)

When the User clicked the button, the corresponding method of your channel will be called with provided arguments.

Note that all such methods MUST return a str as a respond to the action from user, and they MUST NOT raise any exception to its caller. Any exceptions occurred within MUST be expected and processed.

Message delivery

Slave channels SHOULD deliver all messages that the IM provides, including what the User sent outside of this channel. But it SHOULD NOT deliver message sent from the master channel again back to the master channel as a new message.

Implementation details

See SlaveChannel.