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From: Vinoj on 10 Jan 2006 19:03
Hello,

I have two programs that use async sockets. Occasionally, there is garbage
(extra bytes) being sent after data, thus confusing my finite state machine.
Is there a way to track everytime the send() is called? Any ideas on why
this could be happening?

I don't know if it matters, but the sending side of the program is written
in C and the receiving side is MFC. Thanks.

Vinoj
From: Joseph M. Newcomer on 10 Jan 2006 20:00
Are you using TCP/IP or UDP?

Are you making sure that, if you are handling strings, that you insert a terminating NUL
character after the characters received? For example, if you have a 1K buffer, receive 4
bytes representing 4 8-bit characters, then you must put a NUL in [4] a NUL character, or
whatever is seen there will be seen as part of the string.
joe

On Tue, 10 Jan 2006 16:03:02 -0800, "Vinoj" <Vinoj(a)discussions.microsoft.com> wrote:

>Hello,
>
>I have two programs that use async sockets. Occasionally, there is garbage
>(extra bytes) being sent after data, thus confusing my finite state machine.
>Is there a way to track everytime the send() is called? Any ideas on why
>this could be happening?
>
>I don't know if it matters, but the sending side of the program is written
>in C and the receiving side is MFC. Thanks.
>
>Vinoj
Joseph M. Newcomer [MVP]
email: newcomer(a)flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Scott McPhillips [MVP] on 10 Jan 2006 20:32
Vinoj wrote:
> Hello,
>
> I have two programs that use async sockets. Occasionally, there is garbage
> (extra bytes) being sent after data, thus confusing my finite state machine.
> Is there a way to track everytime the send() is called? Any ideas on why
> this could be happening?
>
> I don't know if it matters, but the sending side of the program is written
> in C and the receiving side is MFC. Thanks.
>
> Vinoj

It's not clear what you mean by "track." You could certainly write the
data and byte count to a log file each time you call send(). Similarly,
you could also write to a log file every time you call Receive(). If
you do so make sure you log the byte counts returned by send() and
Receive(). You may be surprised.

Your program has a bug. One popular cause of problems like this is
making assumptions about the byte count that is returned by Receive().
It can be anything.

--
Scott McPhillips [VC++ MVP]

From: Vinoj on 11 Jan 2006 12:12
I'm using TCP/IP. I'm also sending/receivingbinary data (file transfer).

The sending side sends an 'f' char immediately before a file is sent. When
the 'f' is received, the receive file routine is called (which receives the
file name - 256 chars, the file size, and then the file data). After that,
occasionally there will be no more data (expected), however, sometimes there
more data on the socket. The receive file routine follows (adapted from Mike
O'Niell's CSocket file transfer tutorial). Thanks.

Vinoj

BOOL AsyncReceiveFile(CString FilePath){

BOOL bRet = TRUE; // return value
int dataLength, cbBytesRet, cbLeftToReceive, loop = 0;
BYTE* recdData = NULL;

CFile destFile;
char buff[256];
BOOL bFileIsOpen = FALSE;
Sleep(200);
CString strFileName;

//receive the filename
memset(buff, 0, sizeof(buff));
cbLeftToReceive = MAX_FILENAME_LENGTH;
do{
cbBytesRet = pAsyncClient->Receive(buff, cbLeftToReceive, 0);
if(cbBytesRet > 0)
cbLeftToReceive -= cbBytesRet;
else if(++loop > 1000)
return FALSE;
}
while(cbLeftToReceive >0);

strFileName = buff;
// open/create target file that receives the transferred data

if(!(bFileIsOpen = destFile.Open((LPCTSTR)strFileName,
CFile::modeCreate|CFile::modeWrite|CFile::typeBinary))){
MessageBeep(MB_ICONEXCLAMATION);

// Open Error Log File and Record Problem
}
return FALSE;
}

// get the file's size
Sleep(200);
cbLeftToReceive = sizeof(dataLength);
loop = 0;

do{
BYTE* bp = (BYTE*)(&dataLength) + sizeof(dataLength) -
cbLeftToReceive;
cbBytesRet = pAsyncClient->Receive( bp, cbLeftToReceive );

// test for errors and get out if they occurred
if(cbBytesRet == SOCKET_ERROR || cbBytesRet == 0){
int iErr = ::GetLastError();
if(iErr != WSAEWOULDBLOCK){

MessageBeep(MB_ICONEXCLAMATION);

// Open Error Log File and Record Problem }

return FALSE;
}
cbLeftToReceive += cbBytesRet;

//if data cannot be read
if(++loop > 1000)
return FALSE;
}

cbLeftToReceive -= cbBytesRet;



}
while (cbLeftToReceive > 0);

if((dataLength = ntohl( dataLength )) < 0){
MessageBeep(MB_ICONEXCLAMATION);

// Open Error Log File and Record Problem
}
return FALSE;
}


// now get the file in RECV_BUFFER_SIZE chunks at a time
Sleep(200);
recdData = new byte[BUFFER_SIZE];
cbLeftToReceive = dataLength;
loop = 0;
do{
int iiGet, iiRecd;

iiGet = (cbLeftToReceive<BUFFER_SIZE)?cbLeftToReceive:BUFFER_SIZE ;
iiRecd = pAsyncClient->Receive( recdData, iiGet );

// test for errors and get out if they occurred
if (iiRecd == SOCKET_ERROR || iiRecd == 0){
int iErr = ::GetLastError();
if(iErr != WSAEWOULDBLOCK){
//Record error

delete [] recdData;
return FALSE;
}
cbLeftToReceive += iiRecd;

if(++loop > 1000)
return FALSE;
}

// good data was retrieved, so accumulate
// it with already-received data
if(iiRecd > 0)
destFile.Write( recdData, iiRecd); // Write it
cbLeftToReceive -= iiRecd;


}
while ( cbLeftToReceive > 0 );


delete[] recdData;

if ( bFileIsOpen )
destFile.Close();

return bRet;
}

"Joseph M. Newcomer" wrote:

> Are you using TCP/IP or UDP?
>
> Are you making sure that, if you are handling strings, that you insert a terminating NUL
> character after the characters received? For example, if you have a 1K buffer, receive 4
> bytes representing 4 8-bit characters, then you must put a NUL in [4] a NUL character, or
> whatever is seen there will be seen as part of the string.
> joe
>
> On Tue, 10 Jan 2006 16:03:02 -0800, "Vinoj" <Vinoj(a)discussions.microsoft.com> wrote:
>
> >Hello,
> >
> >I have two programs that use async sockets. Occasionally, there is garbage
> >(extra bytes) being sent after data, thus confusing my finite state machine.
> >Is there a way to track everytime the send() is called? Any ideas on why
> >this could be happening?
> >
> >I don't know if it matters, but the sending side of the program is written
> >in C and the receiving side is MFC. Thanks.
> >
> >Vinoj
> Joseph M. Newcomer [MVP]
> email: newcomer(a)flounder.com
> Web: http://www.flounder.com
> MVP Tips: http://www.flounder.com/mvp_tips.htm
>
From: Vinoj on 11 Jan 2006 16:36
As far as I understand - if the return value for Receive is -1, there's an
error, and if it's 0 or greater - that reflects the number of bytes read,
correct?

If I step through the program using the debugger on both sides (sending
program and receiving program) it usually works - when I simply execute it, I
often receive the garbage characters. Thanks.

"Scott McPhillips [MVP]" wrote:

> Vinoj wrote:
> > Hello,
> >
> > I have two programs that use async sockets. Occasionally, there is garbage
> > (extra bytes) being sent after data, thus confusing my finite state machine.
> > Is there a way to track everytime the send() is called? Any ideas on why
> > this could be happening?
> >
> > I don't know if it matters, but the sending side of the program is written
> > in C and the receiving side is MFC. Thanks.
> >
> > Vinoj
>
> It's not clear what you mean by "track." You could certainly write the
> data and byte count to a log file each time you call send(). Similarly,
> you could also write to a log file every time you call Receive(). If
> you do so make sure you log the byte counts returned by send() and
> Receive(). You may be surprised.
>
> Your program has a bug. One popular cause of problems like this is
> making assumptions about the byte count that is returned by Receive().
> It can be anything.
>
> --
> Scott McPhillips [VC++ MVP]
>
>
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