C / C++ / MFC

22-Dec-05 18:47

Hi all. I m using sockets to send file or strings in a TCP/IP simple client/server configuration. The question is, how do i let the sender differentiate b/w sending files and strings? I've read that people send ACK as a ascii character to acknowledge packets. Can i use this as a method to let the receiver know its receiving a file instead?

Pls help me!

Owner drawn22-Dec-05 21:00

Owner drawn

22-Dec-05 21:00

You can use any kind of mutually agreed technique. So that both the client and server understand what happening.

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vikas amin22-Dec-05 22:15

vikas amin

22-Dec-05 22:15

i Dont remember any specific method IN TCP/IP for file or string
u can use a series of NULL char . Using the ACK might create
ambiguity in some case. Cool | :cool:

Vikas Amin
Embin Technology
Bombay
vikas.amin@embin.com

mambohoe8122-Dec-05 23:12

22-Dec-05 23:12

ok thanks. I'll try out these methods. Smile | :)

Btw, does anyone know of any good Winsock programs on this area? Cos i could only find tutorials on simple string sending but not on both.

Gary R. Wheeler24-Dec-05 3:19

Gary R. Wheeler

24-Dec-05 3:19

Assuming that the files you are sending back and forth could contain arbitrary data, you can't use a simple marker character to signal a switch between sending strings and files.

A better approach is to define a message format that tells the receiver what type of data is coming. Here's an example:

struct Message {
  enum {
    String,
    File
  }             Type;
  unsigned int  Length;
  unsigned char Data[1];
};

The first value, Type, tells the receiver what kind of data is coming. The Length value specifies the amount of data to expect. The third value, Data, is actually just a placeholder for the actual data, which will be Length bytes long.

Software Zen:

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mambohoe8124-Dec-05 5:42

24-Dec-05 5:42

This sounds pretty hard to understand for me as i m new to sockets programming and also c++. Have only previously handled some simple programming in c. Could u pls provide me with more details or example?
Thanks for providing me with something anyway.

Gary R. Wheeler24-Dec-05 9:53

Gary R. Wheeler

24-Dec-05 9:53

The way this works is that everything that is sent on the socket is a message. The sender will send a type, a length value, and the number of data bytes specified by the length. The receiver does the corresponding. It reads the type value, then the length, and then reads the number of data bytes specified by the length. Using this approach, you always know what type of data is being sent by the other end of the connection, and how big it is.

I would suggest making two simple test programs, a client program and a server program. You can run both of them at the same time on the same machine using IP address 127.0.0.1. You can then debug both of them simultaneously.

You might try looking at the articles in the Internet & Network Programming[^] section of Code Project. There are a number of good examples of this kind of approach.

Software Zen:

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mambohoe8127-Dec-05 0:47

Why DeviceIoControl always return 0?

27-Dec-05 0:47

In the midst of trying to develop a protocol which can differentiate string/file, i found out that the routine i modified from the website for send file was actually not working!

Below are part of my receiver code which i used for my CAsyncSocket. So i isolated the send string part and juz tried to produce a working part for file transfer. It seems that i have problem receiving the file when i tested e program with messagebox inside the routines. The new file was created at the destination but its just an empty file with 0 bytes.

void CSockDlg::OnReceive()<br />
{<br />
		<br />
			char* pBuf=new char[1025];<br />
			int iBufSize=1024;<br />
			int iRcvd;<br />
		<br />
			CString strLocalFileName;<br />
			iRcvd=m_sConnectSocket.Receive(pBuf,iBufSize);<br />
			pBuf[iRcvd] =NULL; <br />
			strLocalFileName=pBuf;<br />
		<br />
			AfxMessageBox("U get this notification?");<br />
			m_strFileName=strLocalFileName;<br />
			BOOL bRet = GetFileFromRemoteSender(strLocalFileName );<br />
}

Pls help me out! Being stuck for days now.

kkwu21622-Dec-05 17:08

kkwu216

22-Dec-05 17:08

Dear all,
I have tried to get the drive letter of specific USB device. Below is my code. I cannot get a proper return value from DeviceIoControl. Please help and advice me how to make it work. Thanks.

TCHAR diskletter[10];

for(char le='C';le<'T';le++)
{
drive.Format ("%c:",le);
if(GetDriveType(drive)==DRIVE_FIXED||GetDriveType
(drive)==DRIVE_REMOVABLE)
{
sprintf(diskletter,"\\\\.\\%c:",le);
HANDLE handle;
handle=CreateFile(diskletter, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,OPEN_EXISTING, NULL, NULL);
if (handle = INVALID_HANDLE_VALUE)
MessageBox("Open device failed");
else
{
STORAGE_DEVICE_DESCRIPTOR pDevDesc;
STORAGE_PROPERTY_QUERY Query;
DWORD dwOutBytes;
BOOL bResult;
Query.PropertyId= StorageDeviceProperty;
Query.QueryType = PropertyStandardQuery;

bResult=DeviceIoControl(handle,
IOCTL_STORAGE_QUERY_PROPERTY,
&Query, sizeof(STORAGE_PROPERTY_QUERY),
&pDevDesc, pDevDesc.Size,
&dwOutBytes,
(LPOVERLAPPED)NULL);
if(!bResult)
MessageBox("Get bus type failed");
if(pDevDesc.BusType == BusTypeUsb)
m_Editi=m_Editi+le;

CloseHandle(handle);
}
}

replace usp10.dll

dung nam22-Dec-05 14:25

dung nam

22-Dec-05 14:25

hi all!
my objective will be implement setup application (copy fonts and usp10.dll ) on Win XP.
i need replace file usp10.dll with new version but WinXP has a file protected mode. how could i deal that problem, please give me an advice. Smile | :)

writing native windows service using vc++2005

orid22-Dec-05 13:57

orid

22-Dec-05 13:57

Hello,
I recently upgraded my IDE to vc++2005 from vc++6.
I used to write windows services using the ATL Com AppWizard (and choose "service" as the server type).

My problem is that now, in vc++2005, I can't find any wizard for creating a windows service using only native (not managed) c++ code.
The only wizard exist in this new IDE creates a managed code project.

Do you know any way of creating windows services in vc++2005 using only unmanaged code?

Thanks.

Direction needed for MFC VC++ to open a text file

Klerik8222-Dec-05 11:23

Klerik82

22-Dec-05 11:23

Could someone please quide me to an example where MFC will open a text file (.txt) internally within the app. itself for viewing. I am using the VC++ MFC App. win. expoler to do this.
the path of the text file will always be fixed, so i need to know how to read the text file and display it in "read only format" internally on the right pane of the app. once the user clicks display in my UI

Thank you for you help!

Re: Direction needed for MFC VC++ to open a text file

Blake Miller22-Dec-05 11:28

Re: Direction needed for MFC VC++ to open a text file

22-Dec-05 11:28

There is a CP article here on a text file reading class that can even open UNICODE files. I would look for it on CP and use it in your project.

No shirt, no shoes, no brains, no service.

Klerik8222-Dec-05 11:29

Klerik82

22-Dec-05 11:29

Thank you, i am searching for it now!

Help needed. Writing an apps launcher.

cgb14322-Dec-05 9:57

22-Dec-05 9:57

I am trying to write an apps launcher that will also allow sequencing through the running apps User Interfaces. I want it to work something like the MS Office Launch Bar where a button selects the desired app.
I don't know how to launch an app from within an app, or how to bring an app to the foreground.
Any suggestions (or where to find further help) would be appreciated.
Confused | :confused:

cgb143

Blake Miller22-Dec-05 10:11

22-Dec-05 10:11

SetForegroundWindow and CreateProcess are going to be your friends.

No shirt, no shoes, no brains, no service.

cgb14322-Dec-05 11:14

22-Dec-05 11:14

Doing something wrong.

I created a new MFC APP Wizard(exe) project

Added a button to the default dialog box, which generated

BEGIN_MESSAGE_MAP(CTutorDlg, CDialog)<br />
	//{{AFX_MSG_MAP(CTutorDlg)<br />
	ON_WM_SYSCOMMAND()<br />
	ON_WM_PAINT()<br />
	ON_WM_QUERYDRAGICON()<br />
	ON_BN_CLICKED(IDC_BUTTON1, OnButton1)<br />
	//}}AFX_MSG_MAP<br />
END_MESSAGE_MAP()

I added the CreateProcess

void CTutorDlg::OnButton1() <br />
{<br />
	// TODO: Add your control notification handler code here<br />
 CreateProcess("c:\\prog1\\prog.exe",NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);<br />
	<br />
}

But it all crashes when I press the button
(MFC Application has encountered a problem and needs to close.
We are sorry for the inconvenience)
What am I missing (apart from the knowledge Smile | :)

)

Blake Miller22-Dec-05 11:27

22-Dec-05 11:27

Some of the last couple arguments to CreateProcess can not be NULL.
There are a few articles here on CP that can lead you through using CreateProcess.
Otherwise, this should work fine and looks okay.

No shirt, no shoes, no brains, no service.

cgb14322-Dec-05 11:54

22-Dec-05 11:54

You're doing great so far Smile | :)

.
When I click the button the app launches. I lose focus on the launch prog and the graphics are erased.
Also (going back to the original query) how can I launch/control multiple apps.
I looked at some of the articles and they really helped but I can't find this.

Blake Miller22-Dec-05 11:59

22-Dec-05 11:59

When you start another application that way, the new application typically gets the focus. If you don't want it to get focus, use some of the start up flags so the new application's window starts minimized, or SHOW_NA which means to start it in normal window position, but it should not take focus.

What do you mean by control multiple apps? What is it you need to control?

No shirt, no shoes, no brains, no service.

cgb14322-Dec-05 12:20

22-Dec-05 12:20

Multiple copies of the same app , installed in different folders.
I have written an (inhouse) app that communicates with other equipments via RS232 COMMS ports.
Using a port expander I can run up to 6 copies of the app on a single PC (using a local data file to provide Comm Port assignments) thus requiring less PCs. Currently the user navigates to the folder of each installation to execute (or has links on the desktop). I was trying to create a launcher app that would manage the (up to) 6 copies, as the display gets very cluttered.

Blake Miller23-Dec-05 5:13

23-Dec-05 5:13

Save the information from CreateProcess - the thread IF and process handle of each launched program.
A thread in your launcher app can WaitForMultipleObjects on each created process' handle, to later know when it has exited.
When I am trakcing multiple programs, I usually store information into a memory mapped file, and as each of the applications starts up, it sets information into the memory mapped file. If you also store the window handle or thread ID of your launcher app in the memory mapped file, then as each hosted program starts or stops, it can post a window or thread message to the launcher programs window or thread to notify the launcher of relevant activity.

No shirt, no shoes, no brains, no service.