$server = 'target' #(using the FQHN)
$username = 'u_target'
$password = 'u_targetpwd' #(the correct one, of course)

$pass = ConvertTo-SecureString -AsPlainText $password -Force
$Cred = New-Object System.Management.Automation.PSCredential -Argumentlist $username,$pass

$scbScriptBlock = {
# a valid script. For simplicity assume it's
Get-ChildItem C:
}

Invoke-Command -ComputerName $server -Credential $Cred -ScriptBlock $scbScriptBlock

[target] Connecting to remote server failed with following error messages  :
The connection to the specified remote host was refused. Verify that the
WS-Management service is running on the remote host and configured to
listen for requests on the correct port and HTTP URL. For more information,
see the about_Remote_Troubleshooting Help topic.
+ CategoryInfo      : OpenError: (:) [], PSRemotingTransportException
+ FullyQualifiedErrorID : PSSessionStateBroken

Import-Module PSDiagnostics
Enable-PsWsmanCombinedTrace
<run your script>
Disable-PsWsmanCombinedTrace

netstat -ano | findstr /i ":598"
  TCP    0.0.0.0:5985           0.0.0.0:0              LISTENING       4
  TCP    192.168.1.132:49223    192.168.1.131:5985     ESTABLISHED     972
  TCP    [::]:5985              [::]:0                 LISTENING       4

netsh winhttp show proxy

netsh winhttp reset proxy