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 = (-4)
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(0), 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) + 1
    lpCDS.lpData = VarPtr(buff(0))
    For msgId = 0 To 10
        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:0      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:1      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:2      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:3      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:4      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:5      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:6      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:7      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:8      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:9      cbData:28     lpData:你好，我是lichmama。
#WM_COPYDATA  dwData:10     cbData:28     lpData:你好，我是lichmama。