amqtt server not relaying traffic

[sjlongland]

Platform: Debian GNU/Linux 10 (Buster) on AMD64, also reproduced on Gentoo/AMD64
amqtt installed either from pypi or via git using pip.

A simple test without a configuration file… if I open up three terminal windows:

1. I run amqtt (no arguments)… the server starts successfully, binds to port 1883, listens for traffic. So far so good.
2. Second terminal I run amqtt_sub --url mqtt://localhost -t \# (note the backslash: needed on most shells to escape the #), it starts, connects and waits for traffic. amqtt on terminal (1) reports a client has connected.
3. Third terminal, I run amqtt_pub --url mqtt://localhost -t /testing -m 'test message'… it exits without error.

After running that test, no traffic is observed on terminal (2). If I kill amqtt and amqtt_sub, start up another MQTT server such as Mosquitto in place of amqtt, then repeat steps 2 & 3, I see the traffic relayed.

I have also tried setting up a configuration file with a password list and using authenticated users, it still fails to pass through traffic.

The idea of an embeddable and extensible MQTT server is fantastic, so I'm really hoping I can get this working but I'm starting simple first before I try hacking things.

[volkerjaenisch]

I can confirm the findings of @sjlongland .
Going into the code.
Volker

[FlorianLudwig]

@sjlongland thanks for reporting this issue!

The issue is the TopicAccessControlListPlugin - It should be possible to use amqtt without having any ACLs defined but currently it is not. As there a merge request refactoring that plugin (see #42) - we will deal with that first and ensure to add a test reproducing this issue.

I will see if I can help there this week and take on this one afterwards.

[sjlongland]

So, if I understand the bug correctly, if I configure an access control list (which ultimately will be my aim), it will work… it just doesn't work without an ACL due to a logic error?

[sjlongland]

So, others that might want to put the server through its paces… this gets things actually working:

# config.yml
{
    "listeners": {
        "default": {
            "type": "tcp",
            "bind": "0.0.0.0:1883",
        },
    },
    "sys_interval": 10,
    "auth": {
        "allow-anonymous": True,
        "plugins": ["auth_anonymous"],
    },
    "topic-check": {
        "enabled": True,
        "plugins": ["topic_acl"],
        "acl": {
            # username: [list of allowed topics]
            "anonymous": [
                "#"
            ],
        },
    },
}

amqtt -c config.yml -d

[FlorianLudwig]

I am still a bit hesitant to change defaults to far away from hbmqtt.

To fix this issue we should do two things:

1. rework the plugin system
2. improve documenttion how to use amqtt as a stand alone broker