Sendmessage() doesn't send windows messge to the Python window.

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C#

Win32

Python

Tkinter

I am trying to understand python's capability to use Windows Messages with pywin32 library. For this I have created 2 scripts that are supposed to run parralel to each other. One is a client that is supposed to send messages the other is a server that is supposed to print all incoming messages. To use window messeages I have given them gui windows with tkinter library.

But when I run them paralel server doesn't recieve any messages.
Here is the client I use.

def main():
    root = tk.Tk()
    root.title("WM_client")
    root.geometry("400x300")
    root.update()
    root.deiconify()
    #python_hwnd = root.winfo_id()
    python_hwnd = win32gui.FindWindow(None, "WM_client")
    print(f"Server handle is {hex(python_hwnd)}, starting listening")
    target = win32gui.FindWindow(None, "WM_server")
    while True:
        print(target, type(target))
        print(WM_STATEREQUEST, type(WM_STATEREQUEST))
        print(python_hwnd, type(python_hwnd))
        print(f"message to be sent {hex(int(target))}, {WM_STATEREQUEST} , {hex(python_hwnd)}, 0")

        response = win32gui.SendMessage(target, WM_STATEREQUEST, python_hwnd, 0)
        print("server sent message response code", response)
        print("last error given", win32api.GetLastError())
        time.sleep(1)

if __name__ == "__main__":
    main()

And here is the server I use.

def main():
    root = tk.Tk()
    root.title("WM_server")
    root.geometry("400x300")
    root.update()
    root.deiconify()
    # python_hwnd = root.winfo_id()
    python_hwnd = win32gui.FindWindow(None, "WM_server")
    print(f"Server handle is {hex(python_hwnd)}, starting listening")

    while True:
        msg = win32gui.PeekMessage(python_hwnd, 0, 100, win32con.PM_REMOVE)
        if msg[0]  != 0:
            # Extract values from the tuple
            print(msg)
            window_handle, message_type, w_param, l_param, time_posted, (cursor_x, cursor_y) = msg[1]
            if message_type != 96 and message_type != 0:
                print("\nWindow Handle:", window_handle, hex(window_handle))
                print("Message Type:", hex(message_type), message_type)
                print("wParam:", w_param)
                print("lParam:", l_param, "\n")
        client_hwnd = win32gui.FindWindow(None, "WM_client")
        msg = win32gui.PeekMessage(client_hwnd, 0, 100, win32con.PM_REMOVE)
        if msg[0] != 0:
            # Extract
            # values from the tuple
            print(msg)
            window_handle, message_type, w_param, l_param, time_posted, (cursor_x, cursor_y) = msg[1]
            if message_type != 96 and message_type != 0:
                print("\nWindow Handle:", window_handle, hex(window_handle))
                print("Message Type:", hex(message_type), message_type)
                print("wParam:", w_param)
                print("lParam:", l_param, "\n")

What I have tried:

I have checked this using spy++ library and there are no messages falling through to the server side. So I deduced that there is something wrong on client side.

I have also tried to send messages to other applications before with send message and successfuly captured messages with spy++. Strange part is they are the same code.

<pre lang="Python">response = win32api.SendMessage(window_handle, WM_STATEREQUEST, python_hwnd, python_hwnd)