C / C++ / MFC

Choosing an IPC mechanism

5-May-09 1:51

Look at SetEnvironmentVariable[^]

It is a crappy thing, but it's life -^ Carlo Pallini

Re: Environment variable

Jack200955-May-09 2:28

Jack20095

5-May-09 2:28

#include "stdafx.h"
#include <cstdlib>

int _tmain(int argc, _TCHAR* argv[])
{
std::system("set pathTEST=d:");
std::system("set p");
return 0;
}

Re: Environment variable

Stuart Dootson5-May-09 3:16

Stuart Dootson

5-May-09 3:16

For just the current process, you already have answers.

If you want to change the system environment variable values, see this answer[^].

User environment variables are similar, except that their values live in HKEY_CURRENT_USER\Environment

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Rajesh R Subramanian5-May-09 1:46

5-May-09 1:46

I have a console application with no MFC support (I cannot add MFC support due to several reasons). This console executes another process and the new process does a very lengthy operation (I cannot use a thread within the console to do the lengthy operation, as is performed by a third party library that the app links to, which cannot work in console mode). The console app must be notified of the progress of this lengthy operation periodically. Now, when I thought of how to notify the console, I cannot do a PostMessage (there's no window handle), I cannot do a PostThreadMessage (the primary thread does not have a message queue). Therefore, I am considering the following options:

1. Use a named pipe. The console creates the pipe and uses CreateProcess to spawn the other executable, passing the pipe handle while spawning it. The executable write into the pipe and the console reads.
2. Use Overlapped IO
3. Any other suggestions (No, code injection or CreateRemoteThread is not an option that I will consider).

I have the source code of both the applications, but I don't want to do a lot of changes in the console app (thousands of lines, OLD stuff, no docs). However, I'm open to be convinced to do that as well. Thank you!

It is a crappy thing, but it's life -^ Carlo Pallini

ParagPatel5-May-09 2:18

ParagPatel

5-May-09 2:18

Socket communication may become good option for you

Parag Patel
Sr. Software Eng, Varaha Systems

Rajesh R Subramanian5-May-09 2:28

5-May-09 2:28

It looked like a bad option for me, because I will then need to link to the winsock libraries, will have the overhead of sockets, and will need to ensure that the machine will have a loopback adapter. On the contrary, a locally named pipe will execute in kernel mode, the OS has built-in support for it (no additional libraries). So, I had excluded sockets. Smile | :)

Thank you!

It is a crappy thing, but it's life -^ Carlo Pallini

Stuart Dootson5-May-09 3:10

Stuart Dootson

5-May-09 3:10

A mailslot[^]?

That way, the mailslot name is the only hard-coded link between the app calling the third party library and the console app that monitors them - so, it's a highly decoupled design, which is preferable.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Rajesh R Subramanian5-May-09 4:08

5-May-09 4:08

Thanks Stuart, that looks interesting. Now, I'll choose one between Named Pipes and mailslots. Smile | :)

It is a crappy thing, but it's life -^ Carlo Pallini

Randor 5-May-09 6:54

Randor

5-May-09 6:54

Rajesh R Subramanian wrote:
The console app must be notified of the progress of this lengthy operation periodically.

Mailslots, sockets and named pipes.... all for a simple integer percentage value? SendMessage returns a value in its LRESULT which can be used in the console application to retrieve small values such as percentage complete.

Something like this:

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <conio.h>
#include <windows.h>
#include <Psapi.h>
#pragma comment(lib, "psapi")

#define WM_PERCENTAGE WM_USER + 1033

BOOL CALLBACK GetPercentageProc(HWND hWnd, LPARAM lParam)
{
    int nLen = GetWindowTextLength(hWnd);
	TCHAR szTitle[MAX_PATH];
    GetWindowText(hWnd, szTitle, MAX_PATH);
	if(_tcsstr(szTitle,_T("YourApplicationTitle")))
	{
		DWORD dwPID;
		TCHAR szModule[MAX_PATH];
		HMODULE hModule;
		DWORD dwNeeded;
		GetWindowThreadProcessId(hWnd,&dwPID);
		HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ,FALSE,dwPID);
		if(EnumProcessModules(hProcess,&hModule,sizeof(hModule),&dwNeeded))
		{
			GetModuleFileNameEx(hProcess,hModule,szModule,sizeof(szModule));
		}
		else
		{
			GetProcessImageFileName(hProcess,szModule,sizeof(szModule));
		}
		TCHAR * p = _tcsrchr(szModule,_T('\\'));
		if(0 == _tcscmp(++p,_T("YourExecutable.exe")))
		{
			LRESULT dwPercent = SendMessage(hWnd,WM_PERCENTAGE,0,0);
			DWORD dwP =  dwPercent;
			//Do whatever with your percentage value here.
		}
	}
    return TRUE;
}

int main()
{
	EnumWindows(GetPercentageProc, NULL);
	_getch();
	return 0;
}

Note that its recommended to use RegisterWindowMessage [^] for IPC although I did not use it in my example.

Best Wishes,
-David Delaune

Rajesh R Subramanian6-May-09 1:34

DLL performance during the day?

6-May-09 1:34

Hi David,

Isn't SendMessage going to be blocking? I was looking for something that would be asynchronous. (OK, I can use a thread, but I am just asking). I'll try this as well.

Thank you for your suggestions.

It is a crappy thing, but it's life -^ Carlo Pallini

Chesnokov Yuriy5-May-09 0:40

Chesnokov Yuriy

5-May-09 0:40

1) There is some LIB project, with function doing some math, estimating ticks of the function and saving them to file.

2) There is DLL that exports just single function calling the one from LIB

3) There is console application compiled with 2) to invoke the function

4) There is console application compiled with 1) to invoke the function

5) There is some GUI application compiled with 2) to invoke the function

I encounter differences in timings outputed by 5) during the day. It changes from say 2100ms to 1000ms. This morning it run at 1500ms, but this afternoon it runs at 1780ms.

As at the same time 2) runs with exactly the same DLL at 1100ms.

But 4) always runs faster than the rest at say 900ms.

Has anyone encountered such abnormalities. Are they affected at some extent by host project taking the DLL?

Чесноков

CPallini5-May-09 1:45

CPallini

5-May-09 1:45

There is an undocumented effect of Earth Nutation's on the Microsoft DLL calls binding time. Such phenomenon was first theorized by the eminent astrologer Pallinus.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Rajesh R Subramanian5-May-09 1:54

5-May-09 1:54

I heard that if you are using satellite DLLs, the Sun's harsh rays can slow them down.

It is a crappy thing, but it's life -^ Carlo Pallini

CPallini5-May-09 2:27

CPallini

5-May-09 2:27

Yeah, Sun rays are very selective in targeting Microsoft DLLs. Big Grin | :-D

Cleint Server - Connection refused.

Randor 5-May-09 5:36

Randor

5-May-09 5:36

Chesnokov Yuriy wrote:
Has anyone encountered such abnormalities.

No, but this is actually possible. Multimedia timer functions such as timeBeginPeriod[^] will effect the entire operating system. There are *many* applications in the wild which call this function and the authors probably thought it would only have an effect on their application. It effects calls to both timeGetTime and QueryPerformanceCounter because the kernel scheduler itself has been modified.

Call timeBeginPeriod(1) at the beginning of your math function and timeEndPeriod when you are finished.

Best Wishes,
-David Delaune

ganesh.dp4-May-09 23:27

ganesh.dp

4-May-09 23:27

I made one simple client server program.
Server Socket created without any error but client program returns WSAECONNREFUSED error.

For one confirmation i create another one server socket with same port at that time it's not gives any error.
I get confused because it creates two sockets for same port without any error. But this also client gives same error

please help me to get out from this issue.

Server:

m_pserversock = new CServerSocket(this);
	bsucessflag= m_pserversock->Create(m_portno,SOCK_STREAM,NULL);
	status=m_pserversock->GetLastError();
	if(bsucessflag)
	{
		// TODO: Server Listen
		bsucessflag= m_pserversock->Listen(5);
		if(bsucessflag)
		{
			//CString Stemp = m_display.GetWindowText(Stemp,m_display.get
			m_display.SetWindowText("Server Listening\r\n");
		}
		else
		{
			m_display.SetWindowText("Unable to Listen\r\n");
			OnDisconnect();
		}
		int a=m_pserversock->m_hSocket;
	}
	else AfxMessageBox("Unable to Create");

        CSocket *temp;
	temp = new CSocket;
	bsucessflag=temp->Create(m_portno+1,SOCK_STREAM,NULL);
	if(!bsucessflag)
		AfxMessageBox("Error");

CServerSocket,CClientsock is from CSocket.

Client:

m_pClientsock = new CClientsock(this);
		if(m_pClientsock->Create())
		{
			if(m_pClientsock->Connect(dlg.m_Servername,dlg.m_Portno))
			{
				AfxMessageBox("Connected to Server");
				Init();
				m_bIsConnect = TRUE;
				m_Username = dlg.m_Username;
			}
			else 
			{
				int istatus=m_pClientsock->GetLastError();
				
				AfxMessageBox("Not able to Connect Server");
				delete m_pClientsock;
				m_pClientsock = NULL;
			}
		}
		else 
			AfxMessageBox("Not able to Create");

MFC

p_19604-May-09 23:17

p_1960

4-May-09 23:17

hi,
im newbie to MFC can u suggest me any Good book(in which all MFC Classes are explained in detail..So that i will be able to know how to use the classes depends on the requirement...) to start with...im using vs2003

Rajesh R Subramanian4-May-09 23:20

4-May-09 23:20

I'll recommend these:

Programming Windows with MFC by Jeff prosise[^]

Programming Microsoft Visual C++ by David Kruglinski, Scott Wingo and George Shepherd.[^]

MFC Internals by Scott Wingo and George Shepherd[^]

It is a crappy thing, but it's life -^ Carlo Pallini

p_19604-May-09 23:32

p_1960

4-May-09 23:32

Thanks for ur suggestion....

but when i referred jeffprocise i didn"t find the description of all MFC classes
Pls correct me if im wrong...

Rajesh R Subramanian4-May-09 23:36

4-May-09 23:36

It is good enough to start with, and I don't know what do you mean by "all" classes. I reckon that book covered every aspect of programming with MFC and is a very good book.

It is a crappy thing, but it's life -^ Carlo Pallini