@callback close(state :: any()) :: :ok

Callback used for cleaning up the transport layer when the session is closed.

@callback execute(request :: any(), state :: any(), options :: Keyword.t()) ::
  :ok | {:ok, reply :: any()} | {:error, reason :: any()}

Callback for executing requests with a given transport layer.

@callback handle_info(msg :: any(), state :: any()) ::
  {action :: term(), state :: any()}
  | {action :: term(), reply :: any(), state :: any()}

Callback for handling any transport-layer specific messages. Session will redirect any unknown messages to this callback.

It is useful for eg. correctly handling :tcp_close message and similar.

@callback init(url :: URI.t(), options :: Keyword.t()) :: {:ok, any()} | {:error, any()}

Callback for initialization of transport layer implementation.

Upon successful initialization, the callback should return {:ok, state}. Value of state can be anything, but it is recommended that it contains some information that identifies a transport layer instance.