Re: Please Help!!! - CAsyncSocket::OnReceive Not Working for
Microsoft UDP Application (msocudp)
On May 19, 9:57 pm, "Scott McPhillips [MVP]" <org-dot-mvps-at-
scottmcp> wrote:
"Roshan" <ros...@exeltech.com> wrote in message
news:8da3087e-5c1e-4633-b70a-94c533136fb7@t54g2000hsg.googlegroups.com...
Scott,
Hello. Hope you're weekend went well. I am now trying threading with
UDP sockets. On my first try it seems
the OnReceive() is not getting invoked when sending a packet in a
thread.
Please let me know what I might be doing wrong here.
Snippets of my code:
The code can be pretty much thrown away. It seems to have been written
without studying the CAsyncSocket documentation or examples at all. You=
must create the socket in the same thread that you want to receive and sen=
d
from. There are MFC examples that illustrate this. You must use a UI=
type
of MFC thread. There are MFC examples that illustrate this. And, you=
r
thread code only works if you receive the expected 10 packets. UDP IS N=
OT
RELIABLE. You can not and must not assume that you will receive all the=
packets. And finally, what is the point of suspending your main thread
until the socket thread completes? This is fundamentally wrong in any
Windows program: It will lock up your window.
I am not optimistic that you can complete this assignment, and if you must=
rely on UDP to give you all the packets then it is an impossible assignmen=
t
:(
--
Scott McPhillips [VC++ MVP]
Scott,
Hello. I'm afraid that I might have not given you all the correct
details regarding my code for simplicity.
I have built my application ON TOP of the Microsoft UDP sample
application. Here is my code again
along with what file names each snippet belongs too. Before that, let
me answer your question
at the end of your paragraph. The reason I am suspending the main
thread is because in my application I must
first ensure I have ALL the data from all 10 packets before moving
further to process it. I don't show the processing
of data in my snippet for simplicity for you. During the processing
stage, I run other routines that depend on ALL data from the 10
packets.
The result I am currently getting from running my code is that: I am
sending the packet and 10 result packets are being sent back, but
OnReceive is not getting invoked at all which leads to my program
hanging at the WaitForSingleObject() calls.
My Code Snippets again with filenames:
----------------------------------------------------------------------------=
----------------------------------------------------------------------------=
----------------------------
UdpAsySk.h (.h file for Microsoft's UdpAsySk source file)
class CUdpAsySk : public CAsyncSocket
{
...
// Attributes
public:
int m_pktCounter; // MY VARIABLE
HANDLE m_hRcvEvent; // MY VARIABLE
CStringArray m_dataArray; // MY VARIABLE
CDialog* m_pDlg; //back pointers to the main dialog
CString m_sendBuffer; // for async send
int m_nBytesSent;
int m_nBytesBufferSize;
void DoAsyncSendBuff();
...
};
----------------------------------------------------------------------------=
----------------------------------------------------------------------------=
----------------------------
UdpAsySk.cpp (Microsoft's OnReceive function in UdpAsySk source file
with some modification)
void CUdpAsySk::OnReceive(int nErrorCode)
{
OutputDebugString("CUdpAsySk::OnReceive\n");
TCHAR buff[70000];
int nRead;
CString pktType, pktSeq, pktNum, ipAddress, rawData, dvString,
byteString, hexString;
long decimalVal;
nRead = ReceiveFrom(buff, 69999, "192.168.1.200",
1557); ...
packetCounter++;
switch (nRead)
{
case 0:
Close();
break;
case SOCKET_ERROR:
if (GetLastError() != WSAEWOULDBLOCK)
{
if (GetLastError() != WSAEMSGSIZE)
{
TCHAR szError[256];
wsprintf(szError, "OnReceive error: %d", GetLastError());
AfxMessageBox (szError);
}
else
{
AfxMessageBox ("The datagram was too large and was truncated");
CString szTemp(buff);
//((CProdTestDlg*)m_pDlg)->m_strReceive += szTemp;
}
}
break;
default:
if (nRead != SOCKET_ERROR && nRead != 0 )
{
TCHAR szError[256];
wsprintf(szError, "OnReceive bytes: %d", nRead);
buff[nRead] = 0; //terminate the string
CString szTemp(buff);
if (packetCounter ==
10)
{
m_dataArray.Add(szTemp);
SetEvent(m_hRcvEvent); // (*** SET RECEIVE EVENT TO NOTIFY
=
//
UI THREAD IN ProdTestDlg.cpp)
}
...
}
}
...
}
----------------------------------------------------------------------------=
----------------------------------------------------------------------------=
----------------------------
ProdTestDlg.h (.h file for my dialog source file)
struct PRODTESTINFO
{
CUdpAsySk *pUDPSocket;
CString sendString;
int delay; // in milliseconds
HANDLE *pEvent;
CDialog *pDlg;
};
class CProdTestDlg : public CDialog
{
...
// Attributes
private:
PRODTESTINFO *pti;
public:
HANDLE m_hFinishEvent;
CUdpAsySk *m_pUDPSocket;
...
};
----------------------------------------------------------------------------=
----------------------------------------------------------------------------=
----------------------------
ProdTestDlg.cpp (Socket initialization in constructor, Declaration of
UI Thread Function,
and NormalFunction() calling the UI Thread function in my dialog
source file)
...
CProdTestDlg::CProdTestDlg(CWnd* pParent /*=NULL*/)
: CDialog(CProdTestDlg::IDD, pParent)
{
// Setup UDP socket.
if ((m_pUDPSocket = new CUdpAsySk(this)) == NULL)
{
//AfxMessageBox("Failed to allocate UDP socket! Close and restart
app.");
//return TRUE;
AfxMessageBox("Failed to allocate UDP socket! Terminating app.");
exit(0);
}
m_pUDPSocket->m_sendBuffer = ""; //for async send
m_pUDPSocket->m_nBytesSent = 0;
m_pUDPSocket->m_nBytesBufferSize = 0;
m_pUDPSocket->m_sequenceNumber = 0;
m_pUDPSocket->m_ackReceived = false;
m_pUDPSocket->m_dataInArray = false;
if (!m_pUDPSocket->Create(SRC_PORT, SOCK_DGRAM))
{
wsprintf(m_szError, "Failed to create UDP socket: %d! Terminating
app.", m_pUDPSocket->GetLastError());
delete m_pUDPSocket;
m_pUDPSocket = NULL;
AfxMessageBox(m_szError);
//return TRUE;
exit(0);
}
}
...
UINT UDPSocketThread(LPVOID pParam)
{
PRODTESTINFO *ptinfo = (PRODTESTINFO *) pParam;
CUdpAsySk *pUDPSocket = ptinfo->pUDPSocket;
HANDLE *pEvent = ptinfo->pEvent;
pUDPSocket->m_nBytesSent = 0;
pUDPSocket->m_sendBuffer = ptinfo->sendString;
pUDPSocket->m_nBytesBufferSize = ptinfo-
sendString.GetLength() + 1;
pUDPSocket->DoAsyncSendBuff(); (*** WE ARE SENDING THE
PACKET WITH THIS STATEMENT ***)
Sleep(ptinfo->delay);
WaitForSingleObject(pUDPSocket->m_hRcvEvent, INFINITE); //
WAIT FOR RECEIVE EVENT
SetEvent(*pEvent); // (*** SET COMPLETION EVENT TO NOTIFY
MAIN THREAD TO CONTINUE ***)
delete ptinfo;
return 0;
}
...
void CProdTestDlg::NormalFunction(int hexNum)
{
CString sendString, verString = "01", seqString,
twoByteHexAddInfo;
m_cmdString = "02";
twoByteHexAddInfo.Format("%04x", hexNum);
seqString.Format("%02x", m_pUDPSocket->m_sequenceNumber);
sendString = verString + seqString + m_cmdString +
twoByteHexAddInfo;
// *** Must pass in an allocated param object to
AfxBeginThread() ***
pti = new PRODTESTINFO();
pti->pUDPSocket = m_pUDPSocket;
pti->sendString = sendString;
pti->delay = 10;
pti->pEvent = &m_hFinishEvent;
AfxBeginThread(UDPSocketThread, pti); *** CALLING THE
THREAD HERE! ****
WaitForSingleObject(m_hFinishEvent, INFINITE); // WAIT
FOR COMPLETION EVENT THEN CONTINUE
=
//
AND PROCESS ALL DATA FROM 10 PACKETS
}