C++ Socket disconnects intermittently

Question

I'm new to socket programming and we have a running MFC client application over the network whose socket for some reason disconnects intermittently at least once a day. It's not a problem with the network because other network apps are running just fine. I noticed something in the logs however, that a database error occurs more or less 10 mins before socket disconnects. Something like :

DB ERROR: ADO Error 1 (s)
select l.LABOID, l.LABOCODE, l.LABOCREDATE, l.LABOTEXT, l.SHORTTEXT,     l.LISACCOUNTINGMODE, l.ADDRESS1, l.ADDRESS2, l.POSTALCODE, l.CITY, l.STATE, l.COUNTRY, the  . TELEPHON, l.FAX, l.EMAIL, l.TELEPHON2, l.NATIONALCODE, l.FIRSTITEMID, l.ALTERNATECODE, l.LABOSERVICEID, l.STARTVALIDDATE, l.ENDVALIDDATE, l.LOGUSERID, l.LOGDATE, b.DICBINARYID , b.OBJECTLINK, b.OBJECTTYPE, b.DICBINARYTYPE, b.BINARYDATE, b.BINARYMIMETYPE, b.BINARYSIZE, b.LOGUSERID, b.LOGDATE, b.BINARYOBJECT, (select count (*) from d DICT_LABO_TO_DEVICE Where l.LABOID = d.LABOID) as NB_DEVICES from DICT_LABORATORIES l, b DICT_BINARY_DATA Where l.ENDVALIDDATE is null and l.LABOCODE like '%%' and l.LABOID b.OBJECTLINK = (+) and b.DICBINARYTYPE (+) = 1 and b . OBJECTTYPE (+) = 7 AND LABOID IN (1) order by l.LABOCODE

ORA-00936: missing expression of
Error: 0x80040e14

On debug mode, I found out that thread is still running but socket is not connected. I could not pinpoint what caused it to disconnect. Is it advisable to issue a reconnect? Here's the code block :

if (m_pClientSocket->IsThreadStillRunning())
  {
    if(m_pClientSocket->m_boSocketConnected)
    {
      dwNbSent_L = *pdwBufferSize_P;        
      m_pClientSocket->Write(pbyBuffer_P, *pdwBufferSize_P);
      iotResult_L = IOTRANS_RESULT_SUCCESS;
    }
    else
    {
      m_pobjSession->Write(MSG_ERROR,TRACE_LOW
                          ,_T("%s Client socket is not connected")
                          ,(LPCTSTR)m_strLastErrFunc);
      iotResult_L = IOTRANS_RESULT_FAILED;
      SetError(ERROR_SOCKET_NOT_CONNECTED, _T("Client socket is not connected"), m_strLastErrFunc);
    }
  }

Can anyone give me a jumpstart or a list of items to check to prevent this from happening?

What are you connected to? Is the network connection dropping? Is the client disconnecting? We have nowhere near the required information to help with this. — Jonathon Reinhart, Oct 25 '12 at 04:09
there's not a problem with the network connection, but the client disconnects after getting this error. — Owen, Oct 25 '12 at 04:55
I'd venture a guess and say that the error handling code that sees the database error then decides to shut down the connection. — Simon Richter, Oct 25 '12 at 07:05

alk · Accepted Answer · 2012-10-25T09:16:30.200

This is most likley not a network error.

The Oracle DB can not parse the SQL statment (leading to error ORA-00938), the ADO Layer on top translates the Oracle error into ADO error 0x80040e14 which simply means 'The command contained one or more errors.'.

This is expected to ba a bug in your application.

What you could do is:

Check (debug) your application, on how it creates its SQL statments.
Check your database, whether some changes (dropped tables/views or rename/deleted columns) where applied, which the application isn't aware of.

C++ Socket disconnects intermittently

1 Answers1