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README.md

Using Sirius

First point your bridge at your laptop, port 5002 (or similar).

Then run:

$ bin/gunicorn -k flask_sockets.worker manage:app -b 0.0.0.0:5002 -w 1

Navigate browser to http://127.0.0.1:5002/

Environment variables

The server can be configured with the following variables:

TWITTER_CONSUMER_KEY=...
TWITTER_CONSUMER_SECRET=...
FLASK_CONFIG=...

For dokku this means using e.g.:

dokku config:set sirius FLASK_CONFIG=heroku
dokku config:set sirius TWITTER_CONSUMER_KEY=DdrpQ1uqKuQouwbCsC6OMA4oF
dokku config:set sirius TWITTER_CONSUMER_SECRET=S8XGuhptJ8QIJVmSuIk7k8wv3ULUfMiCh9x1b19PmKSsBh1VDM

Creating fake printers and friends

Resetting the actual hardware all the time gets a bit tiresome so there's a fake command that creates unclaimed fake little printers:

$ ./manage.py fake printer
[...]
Created printer
     address: 602d48d344b746f5
       DB id: 8
      secret: 66a596840f
  claim code: 5oop-e9dp-hh7v-fjqo

Functionally there is no difference between resetting and creating a new printer so we don't distinguish between the two.

To create a fake friend from twitter who signed up do this:

$ ./manage.py fake user stephenfry

You can also claim a printer in somebody else's name:

$ ./manage.py fake claim b7235a2b432585eb quentinsf 342f-eyh0-korc-msej testprinter

Sirius Architecture

Layers

The design is somewhat stratified: each layer only talks to the one below and above. The ugliest bits are how database and protocol loop interact.

UI / database
----------------------------
protocol_loop / send_message
----------------------------
encoders / decoders
----------------------------
websockets
----------------------------

Information flow (websockets)

The entry point for the bridge is in sirius.web.webapp. Each new websocket connection spawns a gevent thread (specified by running the flask_sockets gunicorn worker) which runs sirius.protocol.protocol_loop.accept immediately. accept registers the websocket/bridge_address mapping in a global dictionary; it then loops forever, decoding messages as they come in.

Claim codes

Devices are associated with an account when a user enters a "claim code". This claim code contains a "hardware-xor" which is derived via a lossy 3-byte hash from the device address. The XOR-code for a device is always the same even though the address changes!

The claim codes are meant to be used "timely", i.e. within a short window of the printer reset. If there are multiple, conflicting claim codes we always pick the most recently created code.

We are also deriving this hardware xor when a device calls home with an "encryption_key_required". In that case we connect the device to the claim code via the hardware-xor and send back the correct encryption key.

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