WinCC Runtime Advanced: Internet Status Monitoring with VBScript

1. Overview

Plant-floor HMIs running Siemens WinCC Runtime Advanced V16 + Update 1 on a Windows PC or Panel PC frequently depend on a 4G/5G USB dongle, satellite backhaul, or a customer-supplied Ethernet connection to reach remote services (telemetry, MQTT brokers, asset dashboards, remote support VPN). When the upstream WAN link drops, operators must know within seconds — without minimizing the runtime window — that the link is down so they do not chase a non-existent PLC fault or restart healthy services.

This reference documents a complete, field-proven approach for driving a green/red internet status icon on a WinCC Runtime Advanced screen using a single internal Boolean tag updated by a VBScript action scheduled in the runtime. The article covers four detection strategies (ICMP ping, Microsoft NCSI HTTP probe, WMI adapter query, NCSI service registry read), TIA Portal tag configuration, scheduler wiring, screen animation, and a verification matrix.

2. Prerequisites

3. Network Status Detection Architecture

Windows reports network state on three distinct layers, and a robust HMI indicator must interrogate the layer that matches the operator's expectation. A green LED on the HMI should mean: "this PC can reach at least one well-known public service over the WAN interface in use right now."

Microsoft documents the Network Connectivity Status Indicator (NCSI) in detail; it is the same logic that drives the globe icon in the Windows system tray. NCSI performs a DNS lookup against dns.msftncsi.com, resolves it to 131.107.255.255, then issues an HTTP GET to http://www.msftncsi.com/ncsi.txt expecting the body Microsoft NCSI. NCSI also issues an ICMP ping to dns.msftncsi.com. Either active probe succeeding sets the tray icon to "connected." Replicating that behavior in VBScript gives the operator the same trust as the Windows icon.

Microsoft NCSI Overview (Windows Server docs)

4. Selecting the Probe Strategy

Recommended pattern: Combine the WMI adapter check with the NCSI HTTP probe. If NetConnectionStatus = 2 (Connected) and the HTTP probe returns 200, drive the tag TRUE. This eliminates false positives when the dongle is associated with the tower but the cellular APN has lost the PDP context.

5. Method 1 — ICMP Ping via WScript.Shell

The simplest probe. WScript.Shell.Exec returns a WshScriptExec object whose StdOut is parsed for the substring TTL= that Windows ping emits on a successful reply.

' Module: mod_InternetCheck
' Purpose: Returns TRUE if the configured IPv4 host replies to ICMP echo.
' Caveat: Some LTE carriers and corporate firewalls block ICMP. Use Method 2 if
'         you observe timeouts even when the link is healthy.
Const PING_TARGET  = "8.8.8.8"
Const PING_COUNT   = "1"
Const PING_TIMEOUT = "1000"   ' milliseconds

Function PingHost(ByVal sTarget)
    Dim oShell, oExec, sLine, bOK
    bOK = False
    Set oShell = CreateObject("WScript.Shell")
    Set oExec  = oShell.Exec("ping -n " & PING_COUNT & " -w " & PING_TIMEOUT & " " & sTarget)

    ' Guard against runaway processes: 5 s hard ceiling on stdout drain.
    Dim tStart : tStart = Timer
    Do While oExec.Status = 0 And (Timer - tStart) < 5
        WScript.Sleep 100
    Loop

    Do While Not oExec.StdOut.AtEndOfStream
        sLine = oExec.StdOut.ReadLine
        If InStr(1, sLine, "TTL=", vbTextCompare) > 0 Then
            bOK = True
            Exit Do
        End If
    Loop

    Set oExec  = Nothing
    Set oShell = Nothing
    PingHost = bOK
End Function

6. Method 2 — NCSI HTTP Probe via WinHttpRequest

This is the recommended primary probe. The NCSI text file at http://www.msftncsi.com/ncsi.txt is the same URL Windows queries; the expected body is exactly Microsoft NCSI. Set aggressive timeouts because a stalled probe will block the scheduler and freeze your tag updates.

' Module: mod_NCSIProbe
' Purpose: Replicates the Microsoft NCSI active probe. Returns TRUE only when
'          DNS resolution and HTTP both succeed and the body matches.
Const NCSI_URL     = "http://www.msftncsi.com/ncsi.txt"
Const NCSI_BODY    = "Microsoft NCSI"
Const NCSI_TIMEOUT = 1500   ' ms (resolve + connect + send + receive)

Function ProbeNCSI()
    Dim oHTTP, sBody
    ProbeNCSI = False
    On Error Resume Next
    Set oHTTP = CreateObject("WinHttp.WinHttpRequest.5.1")
    If oHTTP Is Nothing Then Exit Function

    oHTTP.SetTimeouts NCSI_TIMEOUT, NCSI_TIMEOUT, NCSI_TIMEOUT, NCSI_TIMEOUT
    oHTTP.Open "GET", NCSI_URL, False
    oHTTP.SetRequestHeader "User-Agent", "WinCC_NCSI/1.0"
    oHTTP.Send

    If Err.Number = 0 Then
        If oHTTP.Status = 200 Then
            sBody = oHTTP.ResponseText
            If InStr(1, sBody, NCSI_BODY, vbTextCompare) > 0 Then
                ProbeNCSI = True
            End If
        End If
    End If
    On Error Goto 0
    Set oHTTP = Nothing
End Function

7. Method 3 — WMI Network Adapter Enumeration

Use WMI to confirm the cellular adapter is actually NetConnectionStatus = 2 (Connected) before trusting any application-layer probe. This stops a false green LED when the dongle is enumerated but has no IP address.

' Module: mod_WMIAdapter
' Purpose: Inspect each Win32_NetworkAdapter and return TRUE if any enabled
'          adapter reports a connected link state. Optionally filter by name
'          substring (e.g., the LTE dongle's friendly name).
Function AdapterConnected(Optional ByVal sNameContains = "")
    Dim oWMI, oItems, oItem, bOK
    bOK = False
    On Error Resume Next
    Set oWMI   = GetObject("winmgmts:{impersonationLevel=impersonate}!.\\root\\cimv2")
    Set oItems = oWMI.ExecQuery("Select * from Win32_NetworkAdapter where NetEnabled=True")
    If Err.Number <> 0 Then
        AdapterConnected = False
        Exit Function
    End If

    For Each oItem In oItems
        If Len(sNameContains) = 0 Or InStr(1, oItem.Name, sNameContains, vbTextCompare) > 0 Then
            If oItem.NetConnectionStatus = 2 Then bOK = True  ' 2 = Connected
        End If
    Next
    On Error Goto 0
    AdapterConnected = bOK
End Function

NetConnectionStatus codes (per Win32_NetworkAdapter): 0 = Disconnected, 1 = Connecting, 2 = Connected, 3 = Disconnecting, 4 = Hardware not present, 5 = Hardware disabled, 6 = Hardware malfunction, 7 = Media disconnected, 8 = Authenticating, 9 = Authentication succeeded, 10 = Authentication failed, 11 = Invalid address, 12 = Credentials required.

8. Method 4 — Read the NCSI Service Registry (Caching Layer)

Windows NCSI writes its most recent decision to HKLM\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters\Internet. Reading these keys is near-instant and immune to the network being slow; however it does not replace an active probe, because a reboot, sleep, or a fast disconnect may leave a stale value.

' Module: mod_NCSIStatus
' Purpose: Read Windows' cached NCSI verdict. Returns "Online" or "Offline".
Function ReadNCSIStatus()
    Dim oShell, sVal
    On Error Resume Next
    Set oShell = CreateObject("WScript.Shell")
    sVal = oShell.RegRead("HKLM\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters\Internet\ActiveWebProbeResult")
    If Err.Number <> 0 Then sVal = "Unknown"
    On Error Goto 0
    ReadNCSIStatus = sVal
End Function

Typical values: ActiveWebProbeResult = active (healthy) or inactive (no NCSI). ActiveWebProbeHost = www.msftncsi.com and ActiveWebProbePath = ncsi.txt.

9. TIA Portal Configuration — Internal Bit Tag

1. Open the HMI device in TIA Portal V16.
2. Project tree → HMI Tags → double-click to open the tag table.
3. Add a new tag:

   Field	Value
   Name	InternetStatus_OK
   Connection	Internal tag
   Data type	Bool
   Length	1
   Acquisition mode	Cyclic continuous
   Update cycle	1 s (default 100 ms works for most; see verification)

4. Add an optional second tag for diagnostics: InternetStatus_LastResult as WString[64] storing the textual outcome of the last probe.

10. WinCC Scheduler — VBScript Action

1. Project tree → Schedules → add a new schedule (e.g., Sched_InternetCheck).
2. Set the trigger to a 5 s interval. Do not go below 2 s; the NCSI HTTP probe can take 1.5 s on cellular and you do not want overlapping invocations.
3. Attach a VBScript action and paste the orchestrator below. The action sets the internal tag, never a PLC tag — the operator screen is the only consumer.

' Action: act_InternetCheck (attached to Sched_InternetCheck)
' Period: 5 s. Writes HMI internal tag "InternetStatus_OK".
Option Explicit

Dim bAdapter, bProbe, bOK, sResult

bAdapter = AdapterConnected("")              ' Method 3
bProbe   = ProbeNCSI()                       ' Method 2
bOK      = (bAdapter And bProbe)             ' combine

If bOK Then
    sResult = "Online (" & FormatDateTime(Now, vbShortTime) & ")"
    SmartTags("InternetStatus_OK") = True
Else
    sResult = "Offline (" & FormatDateTime(Now, vbShortTime) & ")"
    SmartTags("InternetStatus_OK") = False
End If

SmartTags("InternetStatus_LastResult") = sResult

11. HMI Screen — Green / Red Indication

1. Open the runtime screen (e.g., Screen_Main).
2. Drop two identical circle objects (Circle_Online, Circle_Offline) on top of each other.
3. For each, open Properties → Animations → Appearance and configure:

   Object	Tag	Value range	Result
   Circle_Online	InternetStatus_OK	0 = invisible, 1 = green fill (#00B050)	Visible when link is up
   Circle_Offline	InternetStatus_OK (inverted via "NOT")	0 = red fill (#C00000), 1 = invisible	Visible when link is down

4. Add a multi-line text field bound to InternetStatus_LastResult for an audit trail visible to operators.
5. Optionally add a tooltip on each circle that explains the failure mode when offline (e.g., "Dongle association lost — check signal LEDs").

The animation logic can be summarized as a small state machine:

                  ProbeNCSI = TRUE
        +--------------------------+
        |                          v
   [Offline]  --- AdapterConnected = TRUE --->  [Online]
        ^                          |
        |                          |
        +------- ProbeNCSI = FALSE +
                OR
        +------- AdapterConnected = FALSE

12. Edge Cases and Field Caveats

13. Verification and Commissioning Checklist

1. Compile and download the HMI project. Confirm the runtime starts in Service mode with the project autoload enabled.
2. Open the screen containing the indicator. The green circle should appear within one probe cycle (≤ 5 s) of runtime start.
3. Pull the USB dongle. The red circle should appear within 10 s (worst case: one cycle for adapter query, one for HTTP timeout).
4. Reinsert the dongle. Confirm the green circle returns and InternetStatus_LastResult updates with the timestamp.
5. Open a CMD prompt and run nslookup www.msftncsi.com to confirm DNS is healthy. Run curl -v http://www.msftncsi.com/ncsi.txt and confirm the body is Microsoft NCSI.
6. From the same Windows account that hosts the runtime, run cscript //nologo "C:\Program Files\Siemens\Automation\WinCC RT Advanced\bin\WCCILpm.exe" (or open the HMI control center) and verify the schedule fires at the configured interval.
7. Disable the WAN link in Device Manager to confirm the offline branch fires without operator intervention.
8. Tail Windows Event Viewer → Application for any COM or scripting errors during a 24 h soak test.

14. Frequently Asked Questions