Return the server certificate a server is using on a specified port

Get-ServerCertificate.ps1

<#
.SYNOPSIS
Return the server certificate a server is using on a specified port
.PARAMETER ComputerName
The remote computer to query
.PARAMETER Port
The remote TCP port to query
.PARAMETER SubjectNameIdentifier
The Subject Name Identifier to send to the server, defaults to the computer name
.PARAMETER SkipCertificateCheck
Bypass certificate trust checking
#>
[CmdletBinding()]
[OutputType( [System.Security.Cryptography.X509Certificates.X509Certificate2] )]
param(
    [Parameter( Mandatory, Position = 1 )]
    [string]
    $ComputerName,
    [uint]
    $Port = '443',
    [string]
    $SubjectNameIdentifier,
    [switch]
    $SkipCertificateCheck
)

#Requires -Version 7.1

try {

    $TcpClient = [System.Net.Sockets.TcpClient]::new( $ComputerName, $Port )
    $SslStream = [System.Net.Security.SslStream]::new( $TcpClient.GetStream(), $false, ( $SkipCertificateCheck ? {$true} : $null ) )
    $SslStream.AuthenticateAsClient(( $SubjectNameIdentifier ?? $ComputerName ))
    $SslStream.RemoteCertificate -as [System.Security.Cryptography.X509Certificates.X509Certificate2]

} catch {

    throw $_.Exception.Message

} finally {
    
    ${SslStream}?.Close()
    ${TcpClient}?.Close()

}