# check-pxeservers.ps1
#
# Monitors the netstat table to see if pxe server communications are broken
# and if so, restarts the service on the target server.
# 
# NOTE: This script should be run on the PXE Manager Server!
#
# Author: Robbie Foust (rfoust@duke.edu)
# Last Modified: November 15, 2007
# 
# Based on a vbscript by Eric Olsen
# (http://juice.altiris.com/download/2671/pxe-monitor)
#

# separate your pxe server IP addresses with commas
$pxeServers = "192.168.0.5","192.168.0.10"

# quick function to convert netstat output into a psobject
function get-netstat {
	$null,$title,$null,$header,$data = netstat -an

	$data | % { 
		$protocol,$local_ip,$local_port,$foreign_ip,$foreign_port,$state = [regex]::replace($_.trimstart(" "),"\s{2,}|[:]",",").split(",")
		new-object psobject |
			add-member -pass -mem NoteProperty Protocol $protocol |
			add-member -pass -mem NoteProperty "Local IP" $local_ip |
			add-member -pass -mem NoteProperty "Local Port" $local_port |
			add-member -pass -mem NoteProperty "Foreign IP" $foreign_ip |
			add-member -pass -mem NoteProperty "Foreign Port" $foreign_port |
			add-member -pass -mem NoteProperty State $state
	}
}

while ($true) {
	$activePxe = @()

	# Run netstat to get a list of all active connections and
	# create a list of IP addresses that are talking to us on port 406
	get-netstat | % {
		if ($_."Local Port" -eq 406) {
			$activePxe += $_."Foreign IP"
		}
	}
	
	# look for the absense of pxe server IPs, and restart their services
	$pxeServers | % {
		if ($activePxe -notcontains $_) {
			write-host "No active connection from $_, checking service..."

			$svc = gwmi -query "select * from win32_service where name = 'Altiris PXE Config Helper'" -computer $_
			
			if ($svc.state -eq "Running") {
				write-host "Service is currently running, attempting restart..."
				if ($svc.stopservice().ReturnValue -ne 0) {
					write-warning "Unable to stop PXE service!"
				}
			start-sleep 10
			}
			else {
				write-host "Service is down, attempting to start it..."
			}

			if ($svc.startservice().ReturnValue -ne 0) {
				write-warning "Unable to start PXE services!"
			}
			else {
				write-host "Service started successfully."
			}
			
			start-sleep 5
		}

	start-sleep 5
	}

}