Question

CSocket problem

Asked by: ekc

I need to make a TCP/IP server, and naturally have decided to use CSocket class.
Need to receive a stream of characters of unknown format and length from a non-MFC client.
I use OnReceive() event to catch the arrival of data, and something like while (CAsyncSocket::Receive()) loop to receive the message, one char in every iteration. But Receive seems to be blocking!
How can I make it non-blocking, or find some other way of receiving whole message and exit the loop?
BTW, can't use CArchive-CFile, because Serialize() doesn´t work with non-MFC data...
Thanks.

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Asked On
2000-06-02 at 13:20:31ID10387480
Tags

csocket

,

carchive

,

problem

Topic

Windows MFC Programming

Participating Experts
3
Points
150
Comments
9

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Answers

 

by: danny_pavPosted on 2000-06-02 at 14:46:17ID: 2883285

use the CArchive::IsBufferEmpty to determine when you have reached the end of your data

 

by: ekcPosted on 2000-06-02 at 14:51:09ID: 2883304

I can't use CArchive as I said. As far as I know, Serialize() saves various CObject-relative information, and could be used only if client is MFC based.
Am I wrong?

 

by: ekcPosted on 2000-06-02 at 14:59:32ID: 2883317

I can't use CArchive as I said. As far as I know, Serialize() saves various CObject-relative information, and could be used only if client is MFC based.
Am I wrong?

 

by: ekcPosted on 2000-06-02 at 15:06:10ID: 2883337

I can't use CArchive as I said. As far as I know, Serialize() saves various CObject-relative information, and could be used only if client is MFC based.
Am I wrong?

 

by: ekcPosted on 2000-06-02 at 15:19:55ID: 2883373

I can't use CArchive as I said. As far as I know, Serialize() saves various CObject-relative information, and could be used only if client is MFC based.
Am I wrong?

 

by: twallPosted on 2000-06-04 at 11:52:56ID: 2887731

The default behaviour is to block until data is received.

Note that unless you decide on a protocol for messages you receive, you have no way of knowing you've reached the "end" of a particular method.  That's the nature of TCP/IP -- you're guaranteed to receive everything sent over the socket, in the order sent, but otherwise there are no inherent "message" boundaries.  While a client may "write" 2048 bytes, you may not necessarily read them in a single chunk, depending on the network configuration between hosts.

One common, simple message format is to send a fixed number of bytes to indicate the length of the following message.  That way, after you've read the length, you know exactly how many more bytes to read to get the complete message.

 

by: saurabh_dasguptaPosted on 2000-06-04 at 13:07:32ID: 2887886

"I use OnReceive() event to catch the arrival of data, and something like while (CAsyncSocket::Receive()) "

Why don't you 'query' the socket to find out how many bytes of data are available for you to read and read only those many ?

Whenever there is arrival of data, OnReceive will be called. If you manage to read all the data that is available during  a single OnReceive, you will keep getting further notifications of data arrival , till the time the client continues to transmit the data or shutsdown the virtual circuit.


You can try the following code:
void MySock::OnReceive(int nErrorCode)
{
int ret_ioctl;
unsigned long      no_of_bytes_readable;
ret_ioctl=ioctlsocket ( m_hSocket,
                        ,FIONREAD,
                        &no_of_bytes_readable);
if (ret_ioctl != 0)      
    {
    //an error occurred, retrieve the error code
    return(WSAGetLastError());
    }
else
    {
    //go ahead and read 'no_of_bytes_readable' number of bytes only,
    char *buffer = ::new char[no_of_bytes_readable]    
    recv (m_hSocket,buffer,no_of_bytes_readable ,0);
    }

}


A good strategy would be to maintain a character buffer member variable, that would get incrementally populated every time OnReceive would be called.

 

by: ekcPosted on 2000-06-05 at 12:31:05ID: 2893496

Comment accepted as answer

 

by: ekcPosted on 2000-06-05 at 12:31:05ID: 2893497

Thanks saurabh_dasgupta,
This IS working.

20120131-EE-VQP-002

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