Function Test-PortAvailable
{
    param(
    [validaterange(1,65535)]
    [int]$Port
    )
    $sockt=New-Object System.Net.Sockets.Socket -ArgumentList 'InterNetwork','Stream','TCP'
    $ip = (Get-NetIPConfiguration).IPv4Address |
        Select -First 1 -ExpandProperty IPAddress
    $ipAddress = [Net.IPAddress]::Parse($ip)
    Try
    {
        $ipEndpoint = New-Object System.Net.IPEndPoint $ipAddress,$port
        $sockt.Bind($ipEndpoint)
        return $true
    }
    Catch [exception]
    {
        return $false
    }
    Finally
    {
        $sockt.Close()
    }
}

PS> Test-PortAvailable -Port 102
True
PS> Test-PortAvailable -Port 1025
False