VB6之WM_COPYDATA

WM_COPYDATA消息是一种进程间通信的一种方式，参考文档如下：

http://msdn.microsoft.com/en-us/library/windows/desktop/ms649011(v=vs.85).aspx

http://www.flounder.com/wm_copydata.htm

http://support.microsoft.com/kb/176058

直接上代码，接收端：

 '模块部分
 'code by lichmama from cnblogs.com
 Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, _
     Source As Any, ByVal Length As Long)
 Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, _
     ByVal nIndex As Long) As Long
 Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, _
     ByVal nIndex As Long, _
     ByVal dwNewLong As Long) As Long
 Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
     ByVal hWnd As Long, _
     ByVal Msg As Long, _
     ByVal wParam As Long, _
     ByVal lParam As Long) As Long

 Private Const WM_COPYDATA = &H4A
 Public Const GWL_WNDPROC = (-)
 Private Type COPYDATASTRUCT
         dwData As Long  '数据标识
         cbData As Long  '数据长度
         lpData As Long  '数据地址
 End Type
 Public lpPrevWndFunc As Long

 Public Function CallbackWndProc(ByVal hWnd As Long, _
     ByVal wMsg As Long, _
     ByVal wParam As Long, _
     ByVal lParam As Long) As Long

     If wMsg = WM_COPYDATA Then
         Dim lpCDS As COPYDATASTRUCT
         Dim buff() As Byte

         Call CopyMemory(lpCDS, ByVal lParam, Len(lpCDS))
         ReDim buff(lpCDS.cbData) As Byte
         Call CopyMemory(buff(), ByVal lpCDS.lpData, lpCDS.cbData)
         Debug.Print "#WM_COPYDATA", "dwData:" & lpCDS.dwData, "cbData:" & lpCDS.cbData, "lpData:" & Left(buff, lpCDS.cbData)
         Erase buff
     End If
     CallbackWndProc = CallWindowProc(lpPrevWndFunc, hWnd, wMsg, wParam, lParam)
 End Function

 '窗体部分
 'code by lichmama from cnblogs.com
 Private Sub Form_Load()
     lpPrevWndFunc = GetWindowLong(Me.hWnd, GWL_WNDPROC)
     Call SetWindowLong(Me.hWnd, GWL_WNDPROC, AddressOf CallbackWndProc)
     Me.Hide
 End Sub

 Private Sub Form_Unload(Cancel As Integer)
     Call SetWindowLong(Me.hWnd, GWL_WNDPROC, lpPrevWndFunc)
 End Sub

接下来是，发送端：

 'code by lichmama from cnblogs.com
 Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hWnd As Long, _
     ByVal wMsg As Long, _
     ByVal wParam As Long, _
     lParam As Any) As Long
 Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, _
     ByVal lpWindowName As String) As Long

 Private Const WM_COPYDATA = &H4A
 Private Type COPYDATASTRUCT
         dwData As Long  '数据标识
         cbData As Long  '数据长度
         lpData As Long  '数据地址
 End Type

 Private Sub Command1_Click()
     Dim hWnd As Long
     Dim lpCDS As COPYDATASTRUCT
     Dim buff() As Byte
     Dim msgId As Long

     hWnd = FindWindow(vbNullString, "Receiver")
     buff = "你好，我是lichmama。"
     '在COPYDATASTRUCT结构中，dwData是[接收端]用来区分不同数据用的。
     '   因为，正常的数据交互中，程序要根据不同的数据做不同处理。
     '   所以，就需要一个dwData这样的变量来做数据区分的标志。
     '   但是，我建议你在给dwData赋值时，最好满足{dwData>=cbData}
     lpCDS.cbData = UBound(buff) +
     lpCDS.lpData = VarPtr(buff())
     For msgId =  To
         lpCDS.dwData = msgId
         Call SendMessage(hWnd, WM_COPYDATA, Me.hWnd, lpCDS)
     Next
 End Sub

接收端收到消息，处理后如下：

#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:      cbData:     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:     cbData:     lpData:你好，我是lichmama。