problem with send function

This is a discussion on problem with send function within the Networking/Device Communication forums, part of the General Programming Boards category; i've been working on wrapper class for winsock functions, and i've been tracing down a lag-style issue (the program freeze-lags) ...

  1. #1
    30 Helens Agree neandrake's Avatar
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    problem with send function

    i've been working on wrapper class for winsock functions, and i've been tracing down a lag-style issue (the program freeze-lags) and it comes from my send function. if someone could help me out and point out any issues that would really help me out.

    Code:
    //typical call would be ::perSend(crchat, 1024);
    //usually though, the crchat is not 1024 in length. i've tried adding an if(...)break to stop
    //when the delimiter was hit, but it didn't do anything.
    
    INT PEER::perSend(CHAR *databuff, INT len)
    {
    	char *zbuff = databuff;
    
    	while (len > 0)
    	{
    		iSentBytes = send(sckPeer, zbuff, 1, 0);
    		if (iSentBytes == SOCKET_ERROR)
    		{
    			if ((iError = WSAGetLastError()) != WSAEWOULDBLOCK)
    				return -1;
    		}
    
    		iTSentBytes += iSentBytes;
    		zbuff++;
    		len--;
    	}
    
    	return iTSentBytes;
    }
    Environment: OS X, GCC / G++
    Codes: Java, C#, C/C++
    AOL IM: neandrake, Email: neandrake (at) gmail (dot) com

  2. #2
    Gawking at stupidity
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    What delimiter? Have you tried running your program through a debugger to see what's going on? Why are you sending the characters one at a time instead of all at once?
    If you understand what you're doing, you're not learning anything.

  3. #3
    and the hat of wrongness Salem's Avatar
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    > if ((iError = WSAGetLastError()) != WSAEWOULDBLOCK)
    And if it is WOULDBLOCK, you skip a character and try and send the next one?

    Do you have something else which you can usefully do for a few mS whilst the network clears some of the backlog?

    How about trying to send as much as possible with each send call, since it returns with the actual amount sent. Using this its possible to advance through the message buffer.
    Code:
    	while (len > 0)
    	{
    		iSentBytes = send(sckPeer, zbuff, len, 0);
    		if (iSentBytes == SOCKET_ERROR)
    		{
    			if ((iError = WSAGetLastError()) != WSAEWOULDBLOCK)
    				return -1;
    		}
    		else
    		{
    			iTSentBytes += iSentBytes;
    			zbuff += iSentBytes;
    			len -= iSentBytes;
    		}
    	}
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  4. #4
    30 Helens Agree neandrake's Avatar
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    thankyou both for replies. I had originally the function to send everything at once, but I had problems with receiving only the first character 1024 times. I changed it this way and it seemed to work. I will definately try salem's approach, however I did some more debugging, and the lag occurs after the perSend function. So it must be a windows thing. the call is sent from a dialog process function, and there is no lag if the perSend function is not called. But the lag occurs after the send (which nothing else happens, except a return to end the function).
    Environment: OS X, GCC / G++
    Codes: Java, C#, C/C++
    AOL IM: neandrake, Email: neandrake (at) gmail (dot) com

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