thread related issue

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hi all,
i am having one problem with threading

i created one dialog based application whose work is to read the data
from serial port and display it.so i created one thred for this work.

means now i got two threads one is application thread and other is
serial communication thread which is created in OnInitDialog.

now everything is working i mean the thread got created it read some
bytes
from port and now it wants to show the data so need to send this data
to main
thread. so i am doing this with ::SendMessage() but it is giving access
violation. i don't know why this is happening and currently i am not
sending the data also i.e. buffer so please help me
below is code (stepwise)

1)In Oninitdialog
THREADPARAM *ptp = new THREADPARAM;
if(ptp)
{
memset(ptp->array,0,30);
strcpy(ptp->array,"Harshal");
ptp->appHandle = this->m_hWnd;
hSerialThread = CreateThread( NULL,
0,
(LPTHREAD_START_ROUTINE)
SerialCommunication,
(LPVOID) NULL,
0,
&dwSerialThreadID);
}



2)Thread function
UINT SerialCommunication(LPVOID pParam)
{
int write_req=0;
THREADPARAM *ptp = (THREADPARAM *)pParam;
while(1)
{
if(write_req == 2)// send write request and read it
{
DWORD length=0;
DWORD dwRead=0;
if (WriteFile(hCom,
SEND_CMD, // pointer to data to write to
file
NOOFBYTE, // number of bytes to write
&length, // pointer to number of bytes
written
NULL) == 0)
{// write failed
write_req = 0;
continue;
}
// writefile succeeded issue readfile
char buffer[MAX_MESSAGE];
memset(buffer,0,MAX_MESSAGE);
if (!ReadFile(hCom, buffer, MAX_MESSAGE, &dwRead,
NULL))
{
write_req = 0;
continue;
}
if(dwRead > 0)
{
//MessageBox(NULL,buffer,"Data with packet",MB_OK);

::SendMessage(ptp->appHandle,MY_SHOW_DATA,0,0);//
error is here
}
write_req = 0;
}
else // only read from port and increment counter
{
DWORD dwRead=0;
char buffer[MAX_MESSAGE];
memset(buffer,0,MAX_MESSAGE);
if (!ReadFile(hCom, buffer, MAX_MESSAGE, &dwRead,
NULL))
{
write_req++;
continue;
}
if(dwRead > 0)
{// you are in thread you need to send message to
// main application
//char a;
HWND hwnd = (HWND)AfxGetApp()->m_pMainWindow;
::SendMessage(ptp->appHandle,MY_SHOW_DATA,0,0);
//MessageBox(NULL,buffer,"Data without
packet",MB_OK);
}
write_req++;

}
}


return 0;
}


3) Sent message function

LRESULT CReadDataDlg::OnShowDataMessage(UINT wParam, LONG lParam)
{
return 0;
}

Thanks and regards
Harshal

.

Relevant Pages

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