u9n / mqtt-sn-gateway

An asyncio Python implementation of a MQTT-SN Gateway

mqtt-sn-gateway

An asyncio Python implementation of a MQTT-SN Gateway

About

We built this since we needed a nice way to interface MQTT-SN devices into our data stream. It is not feature complete as we wrote it quite quick but we hope to add onto it as our need grows. We used a transparent gateway before we built this and once we got over 1000 devices we got problems with the underlying I/O implementation. So this gateway is built as an aggregating gateway with multiple connections to the MQTT broker.

Supported features

• CONNECT - In-memory store of clients
• REGISTER - In-memory store of registered topics in clients
• PUBLISH - Receive a PUBLISH and forward it to MQTT broker

Not supported - yet!

• Gateway ADVERTISE
• LAST WILL and TESTAMENT
• QoS 2 and QoS-1
• SUBSCRIBE
• PINGREG/PINGRESP
• Encapsulated messages
• DTLS encryption

Future work

We would like a Redis-backed client and topic store. This would make it possible to run several instances of the gateway with shared and persistent state for handling higher loads and services outages.

Install

Requires Python 3.7 and higher (since we use asyncio and it is much nicer in 3.7+)

pip install mqtt-sn-gateway

Run via CLI

After installing via pip you can run the server via the command mqtt-sn-server

mqtt-sn-gateway --help

>
Usage: mqtt-sn-gateway [OPTIONS]

  Will assume there is a .env file in the root of the package. This is for
  simple development. To use .env files as in production use the --env-file
  arg to specify path. To make force the application to discard all .env files
  use the --no-env-files flag.

Options:
  --debug          Enable debug logging
  --env-file TEXT  Path to .env file
  --no-env-files   Discard all use of .env files.
  --help           Show this message and exit.

Run via Docker

You can pull the latest docker-image and run via docker if needed.

docker pull quay.io/u9n/mqtt-sn-gateway

Settings

You can use either an .env file or environment variables to set up the gateway.

• HOST: str, Example 0.0.0.0
• PORT: int, Port so serve the gateway. Ex 2883
• BROKER_HOST: str, Broker host, Ex: test.mosquitto.com
• BROKER_PORT: int, Borker port, Default=1883
• BROKER_CONNECTIONS: int: How many connections the gatewat should have to the broker, default=10
• BACK_PRESSURE_LIMIT: int: How many unhandled UDP-packets should be queued up before not receiving more traffic, Default=1000

Extend

It is possible to implement your own client and topic stores. Just supply the gateway an object the follows the correct Protocol.

class ClientStore(Protocol):
    def add_client(self, client: MqttSnClient) -> None:
        ...

    def get_client(self, remote_addr: Tuple[str, int]) -> Optional[MqttSnClient]:
        ...

    def delete_client(self, remote_addr: Tuple[str, int]) -> None:
        ...
    
    
class TopicStore(Protocol):
    def add_topic_for_client(self, client_id: bytes, topic_name: str) -> int:
        ...

    def get_topic_for_client(self, client_id: bytes, topic_id: int) -> Optional[str]:
        ...

Contribute

We appreciate all contributions. File a bug report or fix the issue yourself and submit a pull request.

Commercial support or custom development

We at Utilitarian can help your company with integrating the gateway to your systems. Contact us if you wish to speed up development or make sure your solution has long-term support.

mqtt-sn-gateway's Issues

DISCONNECT on invalid state

When using the in-memory stores all state is lost on a restart. Devices that have done a CONNECT and REGISTER will now try to PUBLISH, but the gateway does not know of them.

If the gateway can't find the client in the store on a PUBLISH it is not sending a PUBACK with return_code=NOT_SUPPORTED.

This is not the best choice. For some devices the devices keeps on trying to publish until it finally sends an new CONNECT.

It would be better to send a DISCONNECT in the client cant be found to indicate to the client it needs a new CONNECT.

Correct handling of QoS-0 and QoS-1

As of now we are always sending messages (publish) to the MQTT-broker with QoS-1. This should be changed so that the actual message is sent with correct QoS.

As QoS -1 and QoS2 is not yet supported it should return an NOT_SUPPORTED error in those cases.

Support Gateway Advertisement and Discovery

To support Gateway Advertisement and Discovery we also needs support of setting a Gatway ID.

Should be easy enough to just have a separate async task that on schedule sends multicast messages and also can receive an push from a search request to send the multcast message sooner.

Correct handling of DUP in PUBLISH

As of now the DUP flag in the PUBLISH message is not used when sending PUBLISH to MQTT-broker. It should be used.