How To Add and Remove Network Connections

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Article ID: 173011 - View products that this article applies to.
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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 As String, 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 MyPass and MyUser arguments are null (use vbNullString), 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
    
    						
Run the project and click on Command1. You will get a Message dialog indicating success or failure. If successful, you should be able to look in Windows Explorer and see the new connection (unless you left lpLocalName undefined, in which case the connection does not show in Explorer). Click Command2 and go to Explorer, where you should see that the connection has been removed.

REFERENCES

For information about limitations using WNetAddConnection2 on different Windows platforms, please see the following article in the Microsoft Knowledge Base:
183366 : INFO: WNetAddConnection2 and Multiple User Credentials


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

Properties

Article ID: 173011 - Last Review: June 29, 2004 - Revision: 2.1
APPLIES TO
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Control Creation Edition
  • Microsoft Visual Basic 4.0 Standard Edition
  • Microsoft Visual Basic 4.0 Professional Edition
  • Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
Keywords: 
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