HOWTO: Add and Remove Network Connections

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0
• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

SUMMARY

This article demonstrates how to programmatically create and remove network connections by using Windows API functions. The following example will add a connection to a network share and will disconnect from the same share.

MORE INFORMATION

NOTE: This code only includes minimal error trapping. It only reports success or failure of the API calls. Any production use of this code should examine the values returned by the API functions and handle the errors appropriately. The most common error constants are listed for this purpose.

Steps to Reproduce Behavior

1. Create a new Standard EXE project.

2. Add a module to the project.

3. Copy and paste the following Declares and Type into the module: (NOTE: If you add this to a Form module, make all entries Private.)

         Declare Function WNetAddConnection2 Lib "mpr.dll" Alias _
         "WNetAddConnection2A" (lpNetResource As NETRESOURCE, _
         ByVal lpPassword As String, ByVal lpUserName As String, _
         ByVal dwFlags As Long) As Long
   

         Declare Function WNetCancelConnection2 Lib "mpr.dll" Alias _
         "WNetCancelConnection2A" (ByVal lpName As String, _
         ByVal dwFlags As Long, ByVal fForce As Long) As Long
   

         Type NETRESOURCE
           dwScope As Long
           dwType As Long
           dwDisplayType As Long
           dwUsage As Long
           lpLocalName As String
           lpRemoteName As String
           lpComment As String
           lpProvider As String
         End Type
   
         Public Const NO_ERROR = 0
         Public Const CONNECT_UPDATE_PROFILE = &H1
         ' The following includes all the constants defined for NETRESOURCE,
         ' not just the ones used in this example.
         Public Const RESOURCETYPE_DISK = &H1
         Public Const RESOURCETYPE_PRINT = &H2
         Public Const RESOURCETYPE_ANY = &H0
         Public Const RESOURCE_CONNECTED = &H1
         Public Const RESOURCE_REMEMBERED = &H3
         Public Const RESOURCE_GLOBALNET = &H2
         Public Const RESOURCEDISPLAYTYPE_DOMAIN = &H1
         Public Const RESOURCEDISPLAYTYPE_GENERIC = &H0
         Public Const RESOURCEDISPLAYTYPE_SERVER = &H2
         Public Const RESOURCEDISPLAYTYPE_SHARE = &H3
         Public Const RESOURCEUSAGE_CONNECTABLE = &H1
         Public Const RESOURCEUSAGE_CONTAINER = &H2
         ' Error Constants:
         Public Const ERROR_ACCESS_DENIED = 5&
         Public Const ERROR_ALREADY_ASSIGNED = 85&
         Public Const ERROR_BAD_DEV_TYPE = 66&
         Public Const ERROR_BAD_DEVICE = 1200&
         Public Const ERROR_BAD_NET_NAME = 67&
         Public Const ERROR_BAD_PROFILE = 1206&
         Public Const ERROR_BAD_PROVIDER = 1204&
         Public Const ERROR_BUSY = 170&
         Public Const ERROR_CANCELLED = 1223&
         Public Const ERROR_CANNOT_OPEN_PROFILE = 1205&
         Public Const ERROR_DEVICE_ALREADY_REMEMBERED = 1202&
         Public Const ERROR_EXTENDED_ERROR = 1208&
         Public Const ERROR_INVALID_PASSWORD = 86&
         Public Const ERROR_NO_NET_OR_BAD_PATH = 1203&
   
   

4. Add two CommandButtons to Form1. These will be Command1 and Command2 by default.

5. Add the following code to Form1, substituting a valid share name for "\\ServerName\ShareName":

         Option Explicit
   

         Private Sub Command1_Click()
         Dim NetR As NETRESOURCE
         Dim ErrInfo As Long
         Dim MyPass, MyUser As String
   

         NetR.dwScope = RESOURCE_GLOBALNET
         NetR.dwType = RESOURCETYPE_DISK
         NetR.dwDisplayType = RESOURCEDISPLAYTYPE_SHARE
         NetR.dwUsage = RESOURCEUSAGE_CONNECTABLE
         NetR.lpLocalName = "X:" ' If undefined, Connect with no device
         NetR.lpRemoteName = "\\ServerName\ShareName"   ' Your valid share
         'NetR.lpComment = "Optional Comment"
         'NetR.lpProvider =    ' Leave this undefined
   
         ' If the UserName and Password arguments are NULL, the user context
         ' for the process provides the default user name.
         ErrInfo = WNetAddConnection2(NetR, MyPass, MyUser, _
         CONNECT_UPDATE_PROFILE)
         If ErrInfo = NO_ERROR Then
           MsgBox "Net Connection Successful!", vbInformation, _
           "Share Connected"
         Else
           MsgBox "ERROR: " & ErrInfo & " - Net Connection Failed!", _
           vbExclamation, "Share not Connected"
         End If
         End Sub
   
         Private Sub Command2_Click()
         Dim ErrInfo As Long
         Dim strLocalName As String
   
         ' You may specify either the lpRemoteName or lpLocalName
         'strLocalName = "\\ServerName\ShareName"
         strLocalName = "X:"
         ErrInfo = WNetCancelConnection2(strLocalName, _
         CONNECT_UPDATE_PROFILE, False)
         If ErrInfo = NO_ERROR Then
           MsgBox "Net Disconnection Successful!", vbInformation, _
           "Share Disconnected"
         Else
           MsgBox "ERROR: " & ErrInfo & " - Net Disconnection Failed!", _
           vbExclamation, "Share not Disconnected"
         End If
         End Sub
   
   

REFERENCES

For more information, please Search on the following topics in either the Win32 Programmer's Reference or The Microsoft Developer Network Library CD-ROM:

• WNetAddConnection2
• WNetCancelConnection2
• NETRESOURCE

Keywords          : vb432 VB4WIN vb5all kbhowto
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbhowto