How many com port in my computer?

In some computer, it have two com port, but some have only one! How do I know how many com port my computer have in VB Code! it is because I want allow the user to select different com port, so I need to know the max. available com port. Thank!

[Bart]

Here ya go:

'// API Declarations
Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, lpSecurityAttributes As SECURITY_ATTRIBUTES, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Public Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long

'// API Structures
Public Type SECURITY_ATTRIBUTES
nLength As Long
lpSecurityDescriptor As Long
bInheritHandle As Long
End Type

'// API constants
Public Const FILE_SHARE_READ = &H1
Public Const FILE_SHARE_WRITE = &H2
Public Const OPEN_EXISTING = 3
Public Const FILE_ATTRIBUTE_NORMAL = &H80


'// Return TRUE if the COM exists, FALSE if the COM does not exist
Public Function COMAvailable(COMNum As Integer) As Boolean
Dim hCOM As Long
Dim ret As Long
Dim sec As SECURITY_ATTRIBUTES

'// try to open the COM port
hCOM = CreateFile("COM" & COMNum & "", 0, FILE_SHARE_READ + _
FILE_SHARE_WRITE, sec, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0)
If hCOM = -1 Then
COMAvailable = False
Else
COMAvailable = True
'// close the COM port
ret = CloseHandle(hCOM)
End If
End Function

Then, use the code below to go through all the possible COM ports, and find if they are available or not. This code presumes that you have a Combo box named cboComm.

Private Sub ListComPorts()
Dim i As Integer

cboComm.Clear
For i = 1 To 16
If COMAvailable(i) Then
cboComm.AddItem i
End If
Next
cboComm.ListIndex = 0
End Sub

[planethax]

Where do I put the

'// API Declarations
Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, lpSecurityAttributes As SECURITY_ATTRIBUTES, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Public Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
 
'// API Structures
Public Type SECURITY_ATTRIBUTES
nLength As Long
lpSecurityDescriptor As Long
bInheritHandle As Long
End Type
 
'// API constants
Public Const FILE_SHARE_READ = &H1
Public Const FILE_SHARE_WRITE = &H2
Public Const OPEN_EXISTING = 3
Public Const FILE_ATTRIBUTE_NORMAL = &H80
 
 
'// Return TRUE if the COM exists, FALSE if the COM does not exist
Public Function COMAvailable(COMNum As Integer) As Boolean
Dim hCOM As Long
Dim ret As Long
Dim sec As SECURITY_ATTRIBUTES
 
'// try to open the COM port
hCOM = CreateFile("COM" & COMNum & "", 0, FILE_SHARE_READ + _
FILE_SHARE_WRITE, sec, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0)
If hCOM = -1 Then
COMAvailable = False
Else
COMAvailable = True
'// close the COM port
ret = CloseHandle(hCOM)
End If
End Function

I put in a new module, didnt work, I tried it on the child form where the combo box is and that did not work either?
Thanx

[CVMichael]

Just FYI... this thread is 7 year old...

I tried the code, and it works for me....

I just tried it like this (with that code in a module):

Dim K As Long
    
    For K = 1 To 16
        Debug.Print K, COMAvailable(K)
    Next K

And I got "True" on comm port 1...

[planethax]

Ok, I put above code in a module called modCom.bas
then put

Private Sub ListComPorts()
Dim i As Integer

cboComm.Clear
For i = 1 To 16
If COMAvailable(i) Then
cboComm.AddItem i
End If
Next
cboComm.ListIndex = 0
End Sub

on my frmConnection (which is a midi child)
even added a MSCom control to form (didnt know if UI had to or not)
still didnt work.
added the snippet you put the so it looked like

Private Sub ListComPorts()
Dim i As Integer
Dim K As Long
For K = 1 To 16
Debug.Print K, COMAvailable(K)
Next K


cboComm.Clear
For i = 1 To 16
If COMAvailable(i) Then
cboComm.AddItem i
End If

still when I run app, there is nothing in the combo box?
I must be missing something simple here?

[CVMichael]

Did you name the combo box "cboComm" ?

[planethax]

Yes it is
I have attached my files, It must be something simple I have overlooked.

[planethax]

I know tjis thread is very Old, but I thought I would post here rather than start a new one as it is on the same issue.

I have tried everything I can think of, and yet still can not get this to work, and I have tried on 4 different Pc's

I have completely started fresh and ree did whole app. but no go.
I deleted file from prev thread and am posting my latest.
Please some one look at this and help me out, I know I have just overlooked something simple.

[planethax]

Thanx.
I had to add

Show
DoEvents
ListComPorts

to the Form_load event