scripts-MediaPC/MQTTmsgOnShutdown/onShutdown.ps1

# onShutdown.ps1
#
# for Windows 10
# - sends an MQTT message on Shutdown and a different one on Restart
# - intended to switch off a Tasmota plug, delayed, after shutdown, but NOT on restart
#
# Prerequisites:
# - download Mosquitto Windows x64 installer
# - extract and copy mosquitto_pub.exe, mosquitto.dll, libssl-1_1-x64.dll and libcrypto-1_1-x64.dll to
#   c:\Tools\mosquitto (or anywhere and change $mosquittoPubPath accordingly)
#
# This script checks if there is a Event 1074 (source: User32) in the System Event Log, that is
# less than 15 seconds old. 
# If so, it checks the content of this event, which contains the info if we are about to 
# "power off" or "restart". 
#
# The script must be set as shutdown script via Windows Group Policy (local GPO)
# Setup: Start -> Run -> gpedit.msc
#   -> Computer Configuration -> Windows Settings -> Scripts (Startup/Shutdown) -> Shutdown
#   -> there, go to tab "PowerShell Scripts" and simply browse for this script. 
#      Group Policy service seems to handle the PS Execution-Policy, 
#      so that it does not have to be set to unrestricted system-wide. 
#      I saved the script to C:\scripts\onShutdown.ps1
#
# Starting it via Task Scheduler on Event 1074 unfortunately does not work, as the script 
# is getting killed before it actually has done anything most times. 
# Via Group Policy, the shutdown will be delayed until the script has finished its work. 

$logFile = "C:\LOG\onShutdown_PS.log"

$mosquittoPubPath = "c:\Tools\mosquitto\mosquitto_pub.exe"
$mqttHost = "mqtt.lan"
#$mqttUser = "username"
#$mqttPwd = "password"

# Topic to send status info to (SHUTDOWN or RESTART)
$mqttStatTopic = "MediaPC/ShutdownEvent"

# Topic/Payload on Shutdown (i.E. send an Event to a Tasmota device)
$mqttTopicOnShutdown = "cmnd/TasmotaMediaPC/event"
$mqttPayloadOnShutdown = "delayedOff"

# Topic/Payload on Restart (i.E. send an Event to a Tasmota device)
#$mqttTopicOnRestart = ""
#$mqttPayloadOnRestart = ""

###########

$scriptPath = split-path -parent $MyInvocation.MyCommand.Definition

$mosquittoPubUserPassword = ""
if($mqttUser -and $mqttPwd -and $mqttUser -ne "" -and $mqttPwd -ne "") {
	$mosquittoPubUserPassword = "-u $mqttUser -P $mqttPwd "
}

$logDate = "{0:yyyy-MM-dd HH:mm:ss}" -f (Get-Date)
if($logFile) { Write-Output $logDate >> $logFile }

Get-WinEvent -FilterHashtable @{logname='System'; id=1074} -MaxEvents 1 | ForEach-Object {
    $ts_event = [datetime]$_.TimeCreated
    $ts_delta = (New-TimeSpan -Start $ts_event).TotalSeconds
    $ts_str = $ts_delta.ToString("#")
	$command = $_.Properties[4].Value
    
    if($logFile) { Write-Output "  last shutdown-event was '$command', $ts_str s ago" >> $logFile }

	if($ts_delta -lt 15) {
		if($logFile) { Write-Output "    ==> OK, publish MQTT messages." >> $logFile }
        if($command -eq "power off") {
			$cmdLine = "$mosquittoPubPath -h $mqttHost $mosquittoPubUserPassword-t $mqttStatTopic -m SHUTDOWN"
			Invoke-Expression $cmdLine
			if($mqttTopicOnShutdown -and $mqttTopicOnShutdown -ne "") {
				$cmdLine = "$mosquittoPubPath -h $mqttHost $mosquittoPubUserPassword-t $mqttTopicOnShutdown -m $mqttPayloadOnShutdown"
				Invoke-Expression $cmdLine
			}
        }
        elseif($command -eq "restart") {
			$cmdLine = "$mosquittoPubPath -h $mqttHost $mosquittoPubUserPassword-t $mqttStatTopic -m RESTART"
			Invoke-Expression $cmdLine
			if($mqttTopicOnRestart -and $mqttTopicOnRestart -ne "") {
				$cmdLine = "$mosquittoPubPath -h $mqttHost $mosquittoPubUserPassword-t $mqttTopicOnRestart -m $mqttPayloadOnRestart"
				Invoke-Expression $cmdLine
			}
        }
    }
    else {
        if($logFile) { Write-Output "    ==> too old. Nothing to do." >> $logFile }
    }
}