 Sending
a message from one machine to another, with the message source originating on a NT system, can be easily done using the NetMessageBufferSend
API. This is essentially the same as using the DOS command NET SEND. The receiving system will display the message appropriately;
when sent to another NT system, the Net Message dialog will pop on screen. When sending to a Windows9x system, the message will be delivered
through the WinPopup utility (which must be running).
By varying the SendTo, SendFrom and Server members of the call, the
alert can be broadcast to specific users or to your own system. |
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'from LMMSG.H
Private Const ERROR_ACCESS_DENIED As Long = 5
Private Const ERROR_BAD_NETPATH As Long = 53
Private Const ERROR_INVALID_PARAMETER As Long = 87
Private Const ERROR_NOT_SUPPORTED As Long = 50
Private Const ERROR_INVALID_NAME As Long = 123
Private Const NERR_BASE As Long = 2100
Private Const NERR_SUCCESS As Long = 0
Private Const NERR_NetworkError As Long = (NERR_BASE + 36)
Private Const NERR_NameNotFound As Long = (NERR_BASE + 173)
Private Const NERR_UseNotFound As Long = (NERR_BASE + 150)
Private Const MAX_COMPUTERNAME As Long = 15
Private Const VER_PLATFORM_WIN32s As Long = 0
Private Const VER_PLATFORM_WIN32_WINDOWS As Long = 1
Private Const VER_PLATFORM_WIN32_NT As Long = 2
Private Type OSVERSIONINFO
OSVSize As Long
dwVerMajor As Long
dwVerMinor As Long
dwBuildNumber As Long
PlatformID As Long
szCSDVersion As String * 128
End Type
'User-defined type for passing
'the data to the Send function
Private Type NetMessageData
sServerName As String
sSendTo As String
sSendFrom As String
sMessage As String
End Type
'NetMessageBufferSend parameters:
'servername: Unicode string specifying the name of the
' remote server on which the function is to
' execute. If this parameter is vbNullString,
' the local computer is used.
'
'msgname: Unicode string specifying the message alias to
' which the message buffer should be sent.
'
'fromname: Unicode string specifying who the message is from.
' This parameter is required to send interrupting messages
' from the computer name. If this parameter is NULL, the
' message is sent from the logged-on user.
'
'msgbuf: Unicode string containing the message to send.
'
'msgbuflen: value that contains the length, in bytes, of
' the message text pointed to by the msgbuf parameter.
Private Declare Function NetMessageBufferSend Lib "netapi32" _
(ByVal servername As String, _
ByVal msgname As String, _
ByVal fromname As String, _
ByVal msgbuf As String, _
ByRef msgbuflen As Long) As Long
Private Declare Function GetComputerName Lib "kernel32" _
Alias "GetComputerNameA" _
(ByVal lpBuffer As String, _
nSize As Long) As Long
Private Declare Function GetVersionEx Lib "kernel32" _
Alias "GetVersionExA" _
(lpVersionInformation As OSVERSIONINFO) As Long
Private Sub Form_Load()
Dim tmp As String
'pre-load the text boxes with
'the local computer name for testing
tmp = Space$(MAX_COMPUTERNAME + 1)
Call GetComputerName(tmp, Len(tmp))
Text1.Text = TrimNull(tmp)
Text2.Text = TrimNull(tmp)
Text3.Text = TrimNull(tmp)
End Sub
Private Sub Command1_Click()
Dim MsgData As NetMessageData
Dim sSuccess As String
With MsgData
.sServerName = Text1.Text
.sSendTo = Text2.Text
.sSendFrom = Text3.Text
.sMessage = Text4.Text
End With
sSuccess = NetSendMessage(MsgData)
Label1.Caption = sSuccess
End Sub
Private Function IsWinNT() As Boolean
'returns True if running WinNT/Win2000/WinXP
#If Win32 Then
Dim OSV As OSVERSIONINFO
OSV.OSVSize = Len(OSV)
If GetVersionEx(OSV) = 1 Then
'PlatformId contains a value representing the OS.
IsWinNT = (OSV.PlatformID = VER_PLATFORM_WIN32_NT)
End If
#End If
End Function
Private Function NetSendMessage(msgData As NetMessageData) As String
Dim success As Long
'assure that the OS is NT ..
'NetMessageBufferSend can not
'be called on Win9x
If IsWinNT() Then
With msgData
'if To name omitted return error and exit
If .sSendTo = "" Then
NetSendMessage = GetNetSendMessageStatus(ERROR_INVALID_PARAMETER)
Exit Function
Else
'if there is a message
If Len(.sMessage) Then
'convert the strings to unicode
.sSendTo = StrConv(.sSendTo, vbUnicode)
.sMessage = StrConv(.sMessage, vbUnicode)
'Note that the API could be called passing
'vbNullString as the SendFrom and sServerName
'strings. This would generate the message on
'the sending machine.
If Len(.sServerName) > 0 Then
.sServerName = StrConv(.sServerName, vbUnicode)
Else
.sServerName = vbNullString
End If
If Len(.sSendFrom) > 0 Then
.sSendFrom = StrConv(.sSendFrom, vbUnicode)
Else
.sSendFrom = vbNullString
End If
'change the cursor and show. Control won't return
'until the call has completed.
Screen.MousePointer = vbHourglass
success = NetMessageBufferSend(.sServerName, _
.sSendTo, _
.sSendFrom, _
.sMessage, _
ByVal Len(.sMessage))
Screen.MousePointer = vbNormal
NetSendMessage = GetNetSendMessageStatus(success)
End If 'If Len(.sMessage)
End If 'If .sSendTo
End With 'With msgData
End If 'If IsWinNT
End Function
Private Function GetNetSendMessageStatus(nError As Long) As String
Dim msg As String
Select Case nError
Case NERR_SUCCESS: msg = "The message was successfully sent"
Case NERR_NameNotFound: msg = "Send To not found"
Case NERR_NetworkError: msg = "General network error occurred"
Case NERR_UseNotFound: msg = "Network connection not found"
Case ERROR_ACCESS_DENIED: msg = "Access to computer denied"
Case ERROR_BAD_NETPATH: msg = "Sent From server name not found."
Case ERROR_INVALID_PARAMETER: msg = "Invalid parameter(s) specified."
Case ERROR_NOT_SUPPORTED: msg = "Network request not supported."
Case ERROR_INVALID_NAME: msg = "Illegal character or malformed name."
Case Else: msg = "Unknown error executing command."
End Select
GetNetSendMessageStatus = msg
End Function
Private Function TrimNull(item As String)
'return string before the terminating null
Dim pos As Integer
pos = InStr(item, Chr$(0))
If pos Then
TrimNull = Left$(item, pos - 1)
Else
TrimNull = item
End If
End Function |
