allow to specify session_id for connect()

[vladak]

The ConnectionManager used by MiniMQTT disallows connecting to the same host/port combination multiple times. Sometimes it is actually handy to be able to create multiple connections, e.g. to test a MQTT broker implementation. This change allows for that by propagating the session_id parameter from connect() to the ConnectionManager.

Tested with CPython and a MQTT broker (called femtomqtt) running on localhost:

#!/usr/bin/env python3

try:
    import logging
except ImportError:
    import adafruit_logging as logging

try:
    from secrets import secrets
except ImportError:
    pass

import ssl
import sys

import adafruit_minimqtt.adafruit_minimqtt as MQTT


def main(session_id):
    logger = logging.getLogger(__name__)
    try:
        console_handler = logging.StreamHandler()
        logger.addHandler(console_handler)
    except Exception:
        pass
    logger.setLevel(logging.DEBUG)

    try:
        import wifi
        import socketpool

        logger.info("Connecting to wifi")
        wifi.radio.connect(secrets["SSID"], secrets["password"], timeout=10)
        logger.info("Connected to wifi")
        pool = socketpool.SocketPool(wifi.radio)
        host = secrets["broker"]
    except ImportError:
        import socket

        pool = socket
        host = "localhost"

    port = 1883
    mqtt_client = MQTT.MQTT(
        broker=host,
        port=port,
        socket_pool=pool,
        ssl_context=ssl.create_default_context(),
        connect_retries=1,
    )

    mqtt_client.logger = logger

    for i in range(2):
        logger.debug(f"connect #{i} with session_id = {session_id}")
        if session_id:
            session_id += f"{i}"
        mqtt_client.connect(session_id=session_id)


if __name__ == "__main__":
    session_id = None
    if len(sys.argv) > 1:
        session_id = sys.argv[1]
    try:
        main(session_id)
    except KeyboardInterrupt:
       pass

With no arguments the program ends with:

connect #0 with session_id = None
Attempting to connect to MQTT broker (attempt #0)
Attempting to establish MQTT connection...
Sending CONNECT to broker...
Fixed Header: bytearray(b'\x10\x14')
Variable Header: bytearray(b'\x00\x04MQTT\x04\x02\x00<')
Receiving CONNACK packet from broker
Got message type: 0x20 pkt: 0x20
Resetting reconnect backoff
connect #1 with session_id = None
Attempting to connect to MQTT broker (attempt #0)
Attempting to establish MQTT connection...
Closing socket
Socket error when connecting: Socket already connected to mqtt://localhost:1883
Traceback (most recent call last):
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py", line 430, in connect
    ret = self._connect(
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py", line 501, in _connect
    self._sock = self._connection_manager.get_socket(
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/venv/lib/python3.10/site-packages/adafruit_connection_manager.py", line 311, in get_socket
    raise RuntimeError(f"Socket already connected to {proto}//{host}:{port}")
RuntimeError: Socket already connected to mqtt://localhost:1883

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/./session_id.py", line 66, in <module>
    main(session_id)
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/./session_id.py", line 58, in main
    mqtt_client.connect(session_id=session_id)
  File "/home/vkotal/Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py", line 464, in connect
    raise MMQTTException(exc_msg) from last_exception
adafruit_minimqtt.adafruit_minimqtt.MMQTTException: ('Connect failure', None)

with any argument 2 connections are created (verified with netstat):

connect #0 with session_id = foo
Attempting to connect to MQTT broker (attempt #0)
Attempting to establish MQTT connection...
Sending CONNECT to broker...
Fixed Header: bytearray(b'\x10\x13')
Variable Header: bytearray(b'\x00\x04MQTT\x04\x02\x00<')
Receiving CONNACK packet from broker
Got message type: 0x20 pkt: 0x20
Resetting reconnect backoff
connect #1 with session_id = foo0
Attempting to connect to MQTT broker (attempt #0)
Attempting to establish MQTT connection...
Sending CONNECT to broker...
Fixed Header: bytearray(b'\x10\x13')
Variable Header: bytearray(b'\x00\x04MQTT\x04\x02\x00<')
Receiving CONNACK packet from broker
Got message type: 0x20 pkt: 0x20
Resetting reconnect backoff

Also tested the same code on Adafruit CircuitPython 9.2.0 on 2024-10-28; Adafruit Feather ESP32S3 4MB Flash 2MB PSRAM with ESP32S3.