Echo whether a process is running on a range of remote computers - vbscript

Question

I'm trying to create a script that will connect to remote computers within an IP address range and then echo which of those is running the explorer.exe process.
When I run the script within a small range (10.2.1.1 - 10.2.1.10), I know that 10.2.1.4 is offline and that 10.2.1.9 and 10.2.1.10 are not Windows based computers and should therefore echo "Explorer.exe is not running" however that doesn't seem to be the case. They appear to return the same result of the previous server. For instance, 10.2.1.3 has 3 instances of Explorer.exe and echo's 3 times, I then get the same result for 10.2.1.4 which is offline.
My script is as follows:
On Error Resume Next
intStartingAddress = InputBox("Please enter a starting address: (e.g. 1)", "Starting Address")
intEndingAddress = InputBox("Please enter an ending address: (e.g. 254)", "Ending Address")
strSubnet = InputBox("Please enter a subnet excluding the last octet: (e.g. 10.2.1.)", "Subnet")
For i = intStartingAddress to intEndingAddress
strComputer = strSubnet & i
Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colProcess = objWMIService.ExecQuery("Select * From Win32_Process Where Name = 'Explorer.exe'")
For Each objProcess in colProcess
If colProcess.Count > 0 Then
Wscript.Echo strComputer & " Explorer.exe is running."
Else
Wscript.Echo strComputer & " Explorer.exe is not running."
End If
Next
Next
Wscript.Echo "That's all folks!"

Answer 1

What makes you believe that non-Windows computers would respond to WMI queries in the first place? For most non-Windows computers the statement
Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" _
& strComputer & "\root\cimv2")
will simply fail, because they don't support WMI (which is short for Windows Management Instrumentation). Because of this error, the objWMIService object remains the same as it was in the previous loop cycle, so your subsequent instructions query the same host you did before. You never see the error, though, because it's masked by the global On Error Resume Next.
This can be mitigated by removing the global On Error Resume Next and changing this loop:
For i = intStartingAddress to intEndingAddress
strComputer = strSubnet & i
Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
...
Next
into something like this:
For i = intStartingAddress to intEndingAddress
strComputer = strSubnet & i
Set objWMIService = Nothing
On Error Resume Next
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" _
& strComputer & "\root\cimv2")
On Error Goto 0
If Not objWMIService Is Nothing Then
...
Else
WScript.Echo strComputer & " cannot be accessed."
End If
Next
You can distinguish between unreachable computers and computers that don't appear to be running Windows by combining the above with a ping test:
Set wmi = GetObject("winmgmts://./root/cimv2")
qry = "SELECT * FROM Win32_PingStatus WHERE Address='" & strComputer & "'"
For Each ping In wmi.ExecQuery(qry)
reachable = (0 = ping.StatusCode)
Next
If reachable Then
If objWMIService Is Nothing Then
'computer is not running Windows
Else
'computer is running Windows
End If
Else
'computer is offline
End If

Answer 2

First: I would move the colProcess.Count check to occur before the colProcess loop. If there are no collections in the object you will not get an echo response.
Second: I would test for a value within the WMI query such as ProcessID and check if it is Null or if it does have a value, meaning that it is actually running.
intStartingAddress = InputBox("Please enter a starting address: (e.g. 1)", "Starting Address")
intEndingAddress = InputBox("Please enter an ending address: (e.g. 254)", "Ending Address")
strSubnet = InputBox("Please enter a subnet excluding the last octet: (e.g. 10.2.1.)", "Subnet")
For i = intStartingAddress to intEndingAddress
strComputer = strSubnet & i
Set objWMIService = Nothing
On Error Resume Next
Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
On Error Goto 0
If objWMIService Is Nothing Then
Wscript.Echo strComputer & " Explorer.exe is not running."
Else
Set colProcess = objWMIService.ExecQuery("Select * From Win32_Process Where Name = 'Explorer.exe'")
If colProcess.Count = 0 Then
Wscript.Echo strComputer & " Explorer.exe is not running."
Else
For Each objProcess in colProcess
If IsNull(objItem.ProcessID) Or Not IsNumeric(objItem.ProcessID) Then
Wscript.Echo strComputer & " Explorer.exe is not running."
Else
Wscript.Echo strComputer & " Explorer.exe is running. (Process ID: " & objItem.ProcessID & ")"
End If
Next
End If
End If
Next
Wscript.Echo "That's all folks!"
EDIT:
Modified Script to take into account the WMI Query will fail on Non-Windows Operating Systems as pointed out by Ansgar Wiechers.