function Select-AvailableWinRmHosts {
    <#
    .SYNOPSIS
    Returns a filtered list of servers that are responding to WinRM requests.

    .PARAMETER ComputerName
        List of servers to test WinRM connections against.

    .PARAMETER ReturnBadServers
        Returns the list of servers that could not be connected to.
    #>
    [CmdletBinding()]
    param(
        [string[]]$ComputerName,
        [switch]$ReturnBadServers
    )

    if(Test-IsCollectionNullOrEmpty $ComputerName) {
        return $null
    }

    $results = Invoke-Parallel -objects $ComputerName -returnObjects -numThreads 32 -script {
        param($server)

        # Invoke a simple script block to verify that WinRM is listening.
        try {
            $success = (1 -eq (Invoke-Command -ComputerName $server -ErrorAction Stop -ScriptBlock { return 1 }))
            if($success) {
                return $server
            } else {
                return $null
            }
        } catch {
            Write-Warning "Select-AvailableWinRMHosts: Could not connect to [$server]`n$_"
            return $null
        }
    }
    $results = ($results | Where-Object { $null -ne $_ })

    # Produce a list of the unavailable servers from the available servers.
    if($ReturnBadServers.IsPresent) {
        $results = $ComputerName | Where-Object { $results -notcontains $_ }
    }

    return $results
}