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CSocket Getting Network failures

Posted on 1998-08-03
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Last Modified: 2013-11-19
I've got a Server app where n clients can connect. I'm using a CMySocket class (derived from CSocket). I've implemented the CMySocket::OnClose( int nErrorCode ) handler. there i got notifications whenever the client or the server are gone (not normally terminated)
My question: how can i get a notification when i.e. the network is down? i did the following: on computer B I run
a client and connected it to the Server (running on comp. A) on comp. A I pulled out the network connector (simulate network failure). None of my two callback functions (either OnReceive(int nErrorCode) nor OnClose( int nErrorCode ) have been called. so how can i get notified about this event?
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Question by:mruff
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by:VEngineer
Comment Utility

I did the same thing as you did, except I derived from class CAsyncSocket.  When I broke the network connection, function OnClose was called.
I'm not sure why it wouldn't do the same for any class derived from CSocket.

Could you post your class MySocket definition (if it isn't exceedingly large) so we can take a look?
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by:mruff
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hello VEngineer,
here's the class interface definition:

// clntsock.h : interface of the CClientSocket class
//

#ifndef __CLNTSOCK_H__
#define __CLNTSOCK_H__

class CMsg;
class CWallPanelServerDoc;

class CClientSocket : public CSocket
{
      DECLARE_DYNAMIC(CClientSocket);
private:
      CClientSocket(const CClientSocket& rSrc);         // no implementation
      void operator=(const CClientSocket& rSrc);  // no implementation

// Construction
public:
      CClientSocket(CWallPanelServerDoc* m_pDoc);

// Attributes
public:
      int m_nMsgCount;
      CSocketFile* m_pFile;
      CArchive* m_pArchiveIn;
      CArchive* m_pArchiveOut;
      CWallPanelServerDoc* m_pDoc;
      BOOL IsAborted() { return m_pArchiveOut == NULL; }

// Operations
public:
      void Init();
      void Abort();
      void SendMsg(CMsg* pMsg);
      void ReceiveMsg(CMsg* pMsg);

// Overridable callbacks
protected:
      virtual void OnReceive(int nErrorCode);
      virtual void OnClose( int nErrorCode );

// Implementation
public:
      virtual ~CClientSocket();

#ifdef _DEBUG
      virtual void AssertValid() const;
      virtual void Dump(CDumpContext& dc) const;
#endif

};

#endif // __CLNTSOCK_H__
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VEngineer earned 50 total points
Comment Utility
I think that the problem lies in the implementation of class CSocket (which is beyond your control).  CSocket switches between non-blocking (asyncronous) and blocking mode (syncronous) under certain circumstances.  This blocking in class CSocket means that the socket keeps waiting for a message and does not send a notification until it recieves one (and it doesn't since it disconnects).

What you have to do is either fool around with CSocket's attributes until you get it to do pure non-blocking, or an easier solution, derive your class from CAsyncSocket, which is known to work properly for your desired application.

I don't work with CSocket a lot, so I'm not sure how to resolve your problem if you want to modify CSocket attributes.  Maybe someone else out here can help you with that if that is your desired track.

If you have further questions, go ahead and stick more comments to the end of this and I'll try to answer them as best I can.
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