Low-latency button press and motion events for homebridge-skybell

skybell-sniff

# /etc/default/skybell-sniff
# Copyright © 2017 Alexander Thoukydides

# SkyBell HD doorbell hostname (or IP address) and name
SKYBELL_HOST=skybell
SKYBELL_NAME='Doorbell'

# Configuration for homebridge-skybell webhooks
HOMEBRIDGE_SKYBELL_PORT=47569
HOMEBRIDGE_SKYBELL_SECRET='My webhooks secret'

# Gateway/router hostname and ssh username
ROUTER_HOST=192.168.0.1
ROUTER_USER=root

# Command used to sniff the doorbell traffic
SKYBELL_CMD_TCPDUMP="ssh ${ROUTER_USER}@${ROUTER_HOST} \"/usr/sbin/tcpdump -lpnttti eth0 host ${SKYBELL_HOST} and port 5683\""

# Command executed when a button press or motion is detected
SKYBELL_CMD_MOTION="curl -d '{\"secret\":\"${HOMEBRIDGE_SKYBELL_SECRET}\",\"name\":\"${SKYBELL_NAME}\"}' http://localhost:${HOMEBRIDGE_SKYBELL_PORT}/homebridge-skybell/trigger/motion"

skybell-sniff.pl

#!/usr/bin/perl
# Copyright © 2017 Alexander Thoukydides

use strict;
use warnings;

use Socket;

# Ensure that standard output is not buffered
$| = 1, select $_ for select STDOUT;

# Process the command line, substituting environment variables
die "$0 SKYBELL-HOST TCPDUMP-COMMAND MOTION-COMMAND\n" unless scalar @ARGV == 3;
foreach my $arg (@ARGV)
{
    $arg =~ s/\$\{(\w+)}/$ENV{$1}/ge;
}
my ($skybell_host, $cmd_tcpdump, $cmd_motion) = @ARGV;

# Timeout (in seconds) to recognise a packet sequence
my $timeout = 10;

# Resolve hostname to a numeric IP address (since that is what tcpdump outputs)
my $skybell_ip_packed = gethostbyname($skybell_host)
    or die "Failed to resolve $skybell_host: $!\n";
my $skybell_ip = inet_ntoa($skybell_ip_packed);

# Start monitoring the SkyBell HD CoAP traffic
open(my $pipe, '-|', $cmd_tcpdump)
    or die "Failed to spawn '$cmd_tcpdump': $!\n";

# Monitor the SkyBell traffic
print "Monitoring SkyBell HD $skybell_host ($skybell_ip)\n";
my $state = 'idle';
my $time = 0;
while (<$pipe>)
{
    # Parse the tcpdump output
    if (!/(\d+):(\d+):(\d+.\d+) IP (\d+(?:\.\d+){3})\.\d+ > [\.\d]+: UDP, length (\d+)\s*$/)
    {
        print "Unexpected tcpdump format: $_";
        next;
    }
    my $time_delta = (($1 *60) + $2) * 60 + $3;
    my $from_skybell = $4 eq $skybell_ip;
    my $length = $5 + 0;
    #printf "%10.6f seconds  %4d bytes %4s %s\n",
    #    $time_delta, $length, ($from_skybell ? 'from' : 'to'), $skybell_host;

    # Check for a timeout from the start of the sequence
    if ($state ne 'idle' and $timeout < ($time += $time_delta))
    {
        print "(Returning to idle)\n";
        $state = 'idle';
        $time = 0;
    }

    # Process the sniffed packet
    if ($state eq 'idle')
    {
        if ($from_skybell and $length == 465)
        {
            print "(Possible motion detected)\n";
            $state = 'armed';
        }
        elsif (not $from_skybell and 800 < $length)
        {
            print "On-demand requested\n";
            $state = 'on-demand';
        }
    }
    elsif ($state eq 'armed')
    {
        if(not $from_skybell and $length == 49)
        {
            print "Motion detected\n";
            $state = 'motion';
            system($cmd_motion) == 0
                or warn "Failed to execute command: $?\n";
        }
    }
}

# Should never reach this point
die "tcpdump process died unexpectedly\n";

skybell-sniff.service

# /etc/systemd/system/skybell-sniff.service
# Copyright © 2017 Alexander Thoukydides

[Unit]
Description=SkyBell HD event detection
After=network-online.target

[Service]
Type=simple
User=root
EnvironmentFile=/etc/default/skybell-sniff
ExecStart=/usr/local/bin/skybell-sniff.pl ${SKYBELL_HOST} ${SKYBELL_CMD_TCPDUMP} ${SKYBELL_CMD_MOTION}
StandardOutput=journal
Restart=on-failure
RestartSec=10
KillMode=process

[Install]
WantedBy=multi-user.target

Hi, it seems that there's a new issue with Skybell binary_sensors. As some of you here really know what you're talking about, please take a look here:
home-assistant/core#11975
Thank you!