Test DNS resolution and SSL connectivity to a given host.

Test-HostConnectivity.ps1

<#
  .SYNOPSIS
  Runs various networking tests to help debug connectivity issues to a specific host.

  .PARAMETER Uri
  The Uri that should be used as the remote host. This should be something like 'www.arc.net' which will be used
  to test by DNS and SSL connectivity as needed.

  .PARAMETER TestDns
  Whether or not to test DNS resolution to the provided Uri

  .PARAMETER TestSsl
  Whether or not to test SSL connectivity and validity to the provided Uri
#>
param (
  [Parameter(Mandatory = $true)]
  [string] $Uri,
  [switch] $TestDns,
  [switch] $TestSsl
)

function Test-DnsResolution {
  param (
    [string] $Uri
  )

  Write-Host "Clearing DNS Client Cache..."
  Clear-DnsClientCache

  if (!$?) {
    throw "Unable to clear Dns Client Cache"
  }
  Write-Host "Successfully cleared DNS Client Cache!" -ForegroundColor DarkGreen

  Write-Host "Attempting to resolve host $($Uri)"
  $resolutionResults = Resolve-DnsName -Name $Uri
  $formattedResults = ($resolutionResults | select-object IPAddress).IPAddress -join ", "

  if (!$?) {
    throw "Unable to resolve host"
  }
  Write-Host "Successfully resolved $($Uri) to $($formattedResults)" -ForegroundColor Blue
}

function Test-SslCertificate {
  param (
    [string] $Uri,
    [string] $Port = "443"
  )
  $Socket = New-Object System.Net.Sockets.Socket(
    [System.Net.Sockets.SocketType]::Stream,
    [System.Net.Sockets.ProtocolType]::Tcp)
  $Socket.Connect($Uri, $Port)
  try {
    $NetStream = New-Object System.Net.Sockets.NetworkStream($Socket, $true)
    $SslStream = New-Object System.Net.Security.SslStream($NetStream, $true)
    $SslStream.AuthenticateAsClient($Uri)
    $RemoteCertificate = [System.Security.Cryptography.X509Certificates.X509Certificate2]$SslStream.RemoteCertificate
    $DisplayData = [ordered]@{}
    $DisplayData.Add("Issuer", $RemoteCertificate.Issuer)
    $DisplayData.Add("Subject", $RemoteCertificate.Subject)
    $DisplayData.Add("Valid From", $RemoteCertificate.NotBefore)
    $DisplayData.Add("Valid Until", $RemoteCertificate.NotAfter)
    $DisplayData.Add("Signature Algorithm", $RemoteCertificate.SignatureAlgorithm.FriendlyName)
    $DisplayData.Add("Serial Number", $RemoteCertificate.SerialNumber)
    $DisplayData.Add("Thumbprint", $RemoteCertificate.Thumbprint)
    $FormattedCertificate = $DisplayData | Format-Table | Out-String

    Write-Host "Successfully retreived SSL certificate " -ForegroundColor Blue
    Write-Host $FormattedCertificate -ForegroundColor DarkGray

    Write-Host "Attempting to validate the retreived certificate from $($Uri)..."
    $CertificateValid = Test-Certificate -Policy SSL -Cert $RemoteCertificate
    if ($CertificateValid) {
      Write-Host "SSL certificate provided by $($Uri) is valid!" -Foreground Blue
    }
    else {
      Write-Error "SSL certificate provided by $($Uri) is invalid"
    }
  }
  catch {
    Write-Error "Unable to test SSL certificate for host, $($Uri). $($PSItem)"
  }
  finally {
    $SslStream.Close()
  }
}

if ($TestDns) {
  Write-Host "Testing DNS resolution for $($Uri)..." -ForegroundColor Yellow
  Test-DnsResolution -Uri $Uri
}

if ($TestSsl) {
  Write-Host "Testing SSL certificate for $($Uri)..." -ForegroundColor Yellow
  Test-SslCertificate -Uri $Uri
}