PRTG Get-HTTPResonse

# ___ ___ _____ ___
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#|  _/   / | || (_ |
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#    NETWORK MONITOR
#-------------------
# Description: The script will check if a URL returns the expected return code and alert you if it doesn't
# Parameters:
# - URL: The site you want to check. Format: www.google.de
# - ResponseCode: The expected numerical response code (overview: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html).
# - DefaultDNS: Use the DNS server that is configured as $DNS inside the script
# - DNS: Use a DNS server of your choice
# - Protocol: http or https are supported.
# - HeaderHost: Modify the host variable in the header of the http request
# ------------------
# (c) 2014 Stephan Linke | Paessler AG

param(
    [string]$URL,
    [int]$ResponseCode,
    [string]$DefaultDNS = "false",
    [string]$DNS = "",
    [string]$protocol = "http",
    [string]$HeaderHost = "www.example.com"
)

# Set a default external DNS server
if($DefaultDNS -eq "true"){ $DNS = "8.8.8.8" }

# Ignore SSL errors
[System.Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}

# If a DNS is set, use it to resolve the URL
if($DNS -ne ""){
    $resolvedIP = Resolve-DnsName $URL -Server $DNS | Select IPAddress
    $URL = $protocol+"://"+$resolvedIP[0].IPAddress+"/"
    $req = [system.Net.WebRequest]::Create($URL)

}
# ...otherwise use the given URL
else{
    $URL = $protocol+"://"+$URL+"/"

    $req = [system.Net.WebRequest]::Create($URL)

}

# Add some headers to the web request (for round robin dns and load balancers)
$req.Host = $HeaderHost;
$req.AllowAutoRedirect=$false
# catch exceptions
try                             { $res = $req.GetResponse() }
catch [System.Net.WebException] { $res = $_.Exception.Response }


# get the numeric response code of the request
$Response = (($res.StatusCode) -as [int])

# and some error handling
if([int]$Response -eq [int]$ResponseCode){
    Write-Host $Response":Page returned HTTP code "$ResponseCode" as expected (used "$URL").";
    exit 0;
}

elseif([int]$Response -eq 0){
    Write-Host $Response":Connection error (used "$URL").";
}

else{
    Write-Host $Response":Page returned "$Response" unexpectedly (used "$URL").";
    exit 1;
}