Add a function to send ping packets

[felipediel]

Some Broadlink firmwares have a watchdog timer to ensure that the device remains connected to the cloud. The devices reboot when they don't receive heartbeat messages from the cloud for more than 3 minutes.

Lots of users want to block access to the internet for privacy reasons and this is causing their devices to reboot periodically. This PR comes to add a function to send heartbeat messages and keep the devices awake even without access to the cloud.

Credits to @marcan, who found the watchdog packet.

Fixes: #458

[felipediel]

@marcan Thanks for your dedication to this. Is this code working?

import broadlink as blk
import time

while True:
    blk.keep_alive("192.168.0.17", 80)  # Example device
    time.sleep(120)

[KTibow]

Any way for me to test this? Just pull the branch and install?

[felipediel]

This test requires a specific environment:

1. Enable UPnP on the router and connect a UPnP device to this router (I connected another router).
2. Block outbound connections from the device on the firewall.
3. Run Home Assistant and set up the Broadlink integration.
4. Wait 10 minutes.
5. Check the remote entity history. Messy.
6. Install this branch on your computer and run this script.
7. Wait 10 minutes.
8. Check the remote entity history. It needs to be ok. 100% availability.

This test is dangerous. We don't know if blocking the device is healthy in the long run. I already have the technology to test, so you don't need to take the risk if you don't want to.

[KTibow]

Okay. I was thinking about testing with the SP4, but I don't control the router I have and your SP4 support PR hasn't been merged yet. Thanks for letting me know.

[felipediel]

I tested. It's working! 🎉

I'm gonna make some fine adjustments and then I release for review...

[KTibow]

Sad that this didn't make it into 0.117, but hopefully this makes it into 0.118!

[marcan]

Sorry for the late test. I tested this in lieu of my previous crontab hack:

import broadlink as blk
import time

while True:
    blk.keep_alive("192.168.7.255", 80)
    time.sleep(120)

(I had to change the parameters from a tuple to separate host/port)

It works fine, I can see the packets going out and no reassociations from my devices.

[felipediel]

Closing to merge with the dev branch. We no longer merge directly into master in order to keep things clean.