C / C++ / MFC

Re: How to communicate between two different app using SendMessage API?

29-Dec-15 19:56

How to communicate between two different app using Send Message API?
Ex:
APP1 having textbox txtBox1
APP2 having textbox txtBox2

In txtbox1 whats ever we type, that needs to be displayed in textbox2.
How to achieve it using SendMessage() API.
Ex code in VC++ is appreciated.

Richard MacCutchan29-Dec-15 22:29

Re: How to communicate between two different app using SendMessage API?

29-Dec-15 22:29

See SendMessage function (Windows)[^]. Use the RegisterWindowMessage function (Windows)[^] to create a message number that is unique to your applications, and set the other two parameters to values that both your applications understand.

Anasuya201530-Dec-15 2:32

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 2:32

Thanks for your help.
I am facing issue in extracting the message.

Code is as follows...
APP1:

C++

int WM_MYMSG = RegisterWindowMessage (L"MYMESSAGE");
HWND hw = FindWindow(NULL, L"Demo");
    LPCTSTR strMsg = L"ClientDemo1";
    //Send that message
   ::SendMessage(hw, WM_MYMSG, NULL, (LPARAM(LPCTSTR)strMsg);

APP2:

C++

LRESULT CDemoDlg::OnMyMsg(WPARAM w, LPARAM l) {

	MSG* p = (MSG*)l;
	LPCTSTR str = (LPCTSTR)p->message;
	MessageBox(str);// No message. But getting the alert while sending message. Need to extract the actual msg here.

	return (LRESULT) 0;
}

Please let me know what changes is needed here by which it'll display "ClientDemo1" in msgbox.

Richard MacCutchan30-Dec-15 2:41

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 2:41

The LPARAM in your sending application is a Unicode string, so why are you casting it to a MSG pointer in the receiving app?

Anasuya201530-Dec-15 3:06

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 3:06

I am just finding the way to print the message.
So you mean to say it is not needed and directly we can use lparam to print the message?

Richard MacCutchan30-Dec-15 4:29

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 4:29

Anasuya2015 wrote:
So you mean to say ...

No, I am saying that whatever type you use in the LPARAM field in the sending app, you must use the same type in the receiver.

David Crow30-Dec-15 10:28

David Crow

30-Dec-15 10:28

Your casting is a bit unclear. It should probably be:

::SendMessage(hw, WM_MYMSG, NULL, (LPARAM) strMsg);
...
LPCTSTR str = (LPCTSTR) l;
MessageBox(str);

The process calling SendMessage() will likely be blocked by the second process since it will be waiting on the message box to be dismissed.

"One man's wage rise is another man's price increase." - Harold Wilson

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Re: How to communicate between two different app using SendMessage API?

Arthur V. Ratz30-Dec-15 2:42

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 2:42

You can use COM automation, Named Pipes, TCP/IP Sockets or whatsoever by implementing your own protocol for interprocess communtication. Smile | :)

Anasuya201530-Dec-15 3:51

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 3:51

Here requirement is restrict to SendMessage() API.
Anyway thanks for your answer. Can you send any sample code for Named Pipes implementation?

Arthur V. Ratz30-Dec-15 4:27

Using Pipes - MSDN Resource

30-Dec-15 4:27

Re: How to communicate between two different app using SendMessage API?

Arthur V. Ratz30-Dec-15 4:29

Re: How to communicate between two different app using SendMessage API?

30-Dec-15 4:29

Also you can reuse SendMessage() API function with its regular list of arguments by implementing your own that encapsulates for example named pipes client mechanism. Smile | :)

Serkan Onat30-Dec-15 9:30

Serkan Onat

30-Dec-15 9:30

You can use WM_COPYDATA[^] message with SendMessage API

There is a linked example on MSDN topic as well

Re: How to communicate between two different app using SendMessage API?

Maximilien6-Jan-16 2:49

Maximilien

6-Jan-16 2:49

This is what we use and it works nicely

I'd rather be phishing!

Conversions in C

ForNow29-Dec-15 8:09

ForNow

29-Dec-15 8:09

Hi
I am wondering if anyone can point me in the right direction
I am getting strange results
When I try to move a DWORD to a char[4] I am running in 64 bit mode and it my understanding that both are 32 bits long
The DWORD has 4 bytes of a ebcdic character string
I want to move the DWORD to char 4 so that I can access every character and convert it to ascii when I try to move 1 of the chars to a unsigned int e.g. Unsigned int c = str[1] the result in c is a negative number maybe the high order bit in str[1] byte is on but by moving it to a unsigned int shouldn't that do away with making the result negative for example moving a D0 results in FFF2
Any help appreciated
Thanks

Richard Andrew x6429-Dec-15 11:44

Richard Andrew x64

29-Dec-15 11:44

I think the problem comes from the way bytes are ordered in memory.

When you treat a 4-byte block as a DWORD, the bytes are not in order from MSB to LSB. It depends upon your hardware.

You can verify this in the debugger. Place a breakpoint anywhere you are using the DWORD variable, and then when it breaks, switch to Disassembly view. (Make sure "Show code bytes" is on.) You'll see the way the bytes are ordered, and it's not what you expect!

The difficult we do right away...
...the impossible takes slightly longer.

ForNow29-Dec-15 11:52

ForNow

29-Dec-15 11:52

That must be it I am doing coding on Hercules MainFrame Emulator when using C Windows function that data doesn't comes back in inverse order

Thanks

Arthur V. Ratz30-Dec-15 2:45

30-Dec-15 2:45

In this case we have to implement an algorithm for packing 4 bytes to a single dword programmatically.
Also, there's no default conversion. DWORD data type is 32 bits = 4 bytes long regardless of it's x64 or x86 mode. Smile | :)

How to call c# callback function from VC++

ForNow30-Dec-15 6:22

ForNow

30-Dec-15 6:22

Hercules has a function FETCH_FW which will take a MainFrame fullword 4 bytes and put in the right sequence for Windows/Linux However it is still coming in EBCDIC and I need to convert it to ASCII thus I need to access every byte and convert it the function FETCH_FW takes as 1st param a DWORD I thought using unsigned char[4] would produce the same result apparently not

shakumar_2128-Dec-15 22:54

shakumar_21

28-Dec-15 22:54

Hi,

How to call C# callback function from VC++ dll?

In my project dll was developed in VC++ and it was
accessed by c# application.

Now I want to call callback function in C# application when particular event was occur in VC++ dll.

Thanks in advance.

Re: How to call c# callback function from VC++

Richard MacCutchan29-Dec-15 0:57

Collecting openions/suggestions for Masters Project (topic: Firewall Optimisation)

29-Dec-15 0:57

See Calling C# .NET methods from unmanaged C/C++ code[^].

RESET USB

Member 1223302928-Dec-15 15:17

Member 12233029

28-Dec-15 15:17

I am developping USB Driver using UMDF1.9 for XP now
I need to reset USB devide from my driver. So I am going to use IOCTL_USB_Hub_Recycle_port to simulate plug off/on.

Does somebody have smaple code hpw to call IOCTL_USB_Hub_Recycle_port

Thanks
Henry

Re: RESET USB

David Crow28-Dec-15 17:01

David Crow

28-Dec-15 17:01

Does this point you in the right direction?

SujithKG28-Dec-15 5:15

SujithKG

28-Dec-15 5:15

Hello everyone..

I'm currently doing my Masters in Computer Network Engg and I have decided to do my Final semester project in optimisation of firewalls.
I'm thinking of implementing firewall optimisation using rule re-ordering and rule conflict detection, but I don't have a clue on how to get started.
I got to know that I can make use of Windows Firewall API (NetFwTypeLib) and work on top of Windows Firewall but I'm not quite sure if this would help me or not.
If you have done anything similar or have some pointers for me please guide me.

Thanks.. Smile | :)

Re: Collecting openions/suggestions for Masters Project (topic: Firewall Optimisation)

Richard MacCutchan28-Dec-15 7:36