PowerShell/Scripts/list-dns-servers.ps1

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<#
.SYNOPSIS
Lists DNS servers
.DESCRIPTION
This PowerShell script measures the latency of public and free DNS servers and lists it.
.EXAMPLE
PS> ./list-dns-servers
Provider IPv4 Latency
-------- ---- -------
AdGuard DNS 94.140.14.14 / 94.140.15.15 222 / 205 ms
...
.LINK
https://github.com/fleschutz/PowerShell
.NOTES
Author: Markus Fleschutz | License: CC0
#>
function CheckDNSServer { param($Provider, $IPv4Pri, $IPv4Sec)
$SW = [system.diagnostics.stopwatch]::startNew()
$null = (nslookup fleschutz.de $IPv4Pri 2>$null)
[int]$Elapsed1 = $SW.Elapsed.TotalMilliseconds
$SW = [system.diagnostics.stopwatch]::startNew()
$null = (nslookup fleschutz.de $IPv4Sec 2>$null)
[int]$Elapsed2 = $SW.Elapsed.TotalMilliseconds
New-Object PSObject -Property @{ Provider=$Provider; IPv4="$IPv4Pri / $IPv4Sec"; Latency="$Elapsed1 / $Elapsed2 ms" }
}
function List-DNS-Servers {
Write-Progress "Loading Data/public-dns-servers.csv..."
$Table = Import-CSV "$PSScriptRoot/../Data/public-dns-servers.csv"
Write-Progress "Measuring latency..."
foreach($Row in $Table) {
CheckDNSServer $Row.PROVIDER $Row.IPv4_PRI $Row.IPv4_SEC
}
Write-Progress -completed " "
}
try {
List-DNS-Servers | Format-Table -property @{e='Provider';width=50},@{e='IPv4';width=32},@{e='Latency';width=15}
exit 0 # success
} catch {
"⚠️ Error in line $($_.InvocationInfo.ScriptLineNumber): $($Error[0])"
exit 1
}