Re: Passing a GUI handle to a socket and Postmessage back to GUI

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Wed, 11 Mar 2009 12:51:56 -0400
"KW" <> wrote in message

I have a MDI application with several child windows and a TCPIP server. I
want to pass the handle (of one child) to a server socket class so it can
post a message to the child window when data is received. When the data is
received by the child window, a listbox will display the data.

I have it working, but I wonder if there is a better way of passing (or
getting) the handle. I have to pass it twice to get it into the
OnReceive() Handler of CServer.cpp.

// Click a button and start the listener - couldn't get it to work in
constructor (handle not created yet?) - "SocketWindow" is UI class
void SocketWindow::OnButton1()
   sockServ = new MySocket(CWnd::m_hWnd); //Is this the best way to
get/pass the handle?

The window's handle does not exist during the window's constructor. The
window's OnCreate or OnInitialUpdate will be called when the handle first
becomes available.

void SocketWindow::OnSockMSG(UINT wParam, long lParam)
   CString * ptr = (CString *)wParam;



It is important that this message handler function provide the exact
function signature that is expected by the message map dispatcher. Assuming
you are using ON_MESSAGE in the message map, this function must be declared:

LRESULT SocketWindow::OnSockMSG(WPARAM wParam, LPARAM lParam)

This will avoid possible stack corruption and 64-bit compatibility issues.

// These 4 lines are from MySocket.h
virtual ~MySocket();
CServer client;
HWND ChildWindowHandle;

In a sockets context it is extremely confusing to name CServer 'client'. In
fact, your MySocket class is the server.

// Constructor MySocket.cpp
MySocket::MySocket(HWND MyHandle)
    ChildWindowHandle = MyHandle;

// MySocket.cpp
void MySocket::OnAccept(int nErrorCode)
    if (nErrorCode == 0)

           // IS THIS A PROBLEM? "client" is declared in CServer.h
           client.HandleToChld = ChildWindowHandle ;

This is workable, but a better OOP design would pass 'this' to the
constructor of the client. Then the client would depend only on the code
that creates it.

Scott McPhillips [VC++ MVP]

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