recv large amounts of data

This is a discussion on recv large amounts of data within the Networking/Device Communication forums, part of the General Programming Boards category; I'm writing a chat bot for PvPGN BnetD. The format will look similar to this: 1010 NAME kpreston 1018 INFO ...

  1. #1
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    recv large amounts of data

    I'm writing a chat bot for PvPGN BnetD. The format will look similar to this:

    1010 NAME kpreston
    1018 INFO "Welcome to PvPGN BnetD 1.5.0!"
    1018 INFO "Type /help for a list of commands."
    1002 JOIN kpreston 0001
    1003 LEAVE somedude 0001
    1003 LEAVE somedude(1) 0001
    1002 JOIN somedude(2) 0001
    1003 LEAVE somedude(2) 0001
    The server is restarted every 3-5 hours. When this happens, approx. 1000 users/bots will reconnect. The issue I'm having is when recv() returns this:

    1010 NAME kpreston\r\n
    1018 INFO "Welcome to PvPGN BnetD 1.5.0!"\r\n
    1018 INFO "Type /help for a list of commands."\r\n
    1002 JOIN kpreston 0001\r\n
    1003 LEAVE somedude 0001\r\n
    1003 LEAVE somedude(1) 0001\r\n
    1002 JOIN somedu
    The buffer gets parsed by "\r\n," and I have an incomplete packet at the end, which will cause undefined behaivor if I don't have a ton of error checking.

    How would you solve this?

    Edit: Speed and efficiency is the MOST important aspect to consider.
    Last edited by kpreston; 10-16-2008 at 12:12 PM.

  2. #2
    Sweet
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    Keep recv'ing until you find a \r\n and process that as a command.
    Woop?

  3. #3
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    Quote Originally Posted by kpreston View Post
    which will cause undefined behaivor if I don't have a ton of error checking.
    I think you just answered your own question.

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    Quote Originally Posted by prog-bman View Post
    Keep recv'ing until you find a \r\n and process that as a command.
    Would I just continue to realloc more space? Would I want to free that memory and malloc a smaller buffer after I've parsed the huge chunk of data?

    I think you just answered your own question.
    No I didn't.

  5. #5
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by kpreston View Post
    Edit: Speed and efficiency is the MOST important aspect to consider.
    I doubt it. Processors are fast. Networks are slow.

    There is no way around the fact that you have to queue up the data while you wait for the line terminators. The code is more complicated but I think your performance worries are unfounded. You aren't considering doing it "wrong" to actually be an option, are you?
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

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    Quote Originally Posted by brewbuck View Post
    I doubt it. Processors are fast. Networks are slow.

    There is no way around the fact that you have to queue up the data while you wait for the line terminators. The code is more complicated but I think your performance worries are unfounded. You aren't considering doing it "wrong" to actually be an option, are you?
    That's the problem. I don't know what "wrong" is. I'm not a very strong C coder, which is why I'm starting this project. What I've thought of doing is similar to this:

    Code:
    char 	*buffer 	= NULL;
    char 	tmp[128] 	= "";
    int 	buffersize 	= 128;
    int 	n		= 0;
    
    buffer = malloc(buffersize * sizeof(char));
    buffer[0] = 0;
    
    while ((n = recv(s, tmp, 128, 0)) > 0) {
    	tmp[n] = 0;
    	if ((strlen(tmp) + strlen(buffer)) >= buffersize) {
    		buffersize = buffersize * 2;
    		buffer = realloc(buffer, buffersize * sizeof(char));
    	}
    	strcat(buffer, tmp);
    	if (buffer[strlen(buffer) - 1] == '\n') {
    		ParseData(buffer);
    		buffersize = 128;
    		free(buffer);
    		buffer = malloc(buffersize * sizeof(char));
    		buffer[0] = 0;
    	}
    }

  7. #7
    and the hat of wrongness Salem's Avatar
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    But there's nothing to say that 3 message fragments might be

    1010 NAME kpreston\r\n1018 INFO
    "Welcome to PvPGN BnetD 1.5.0!"\r
    \n1018 INFO "Type /help for a list of commands."\r\n

    Or for that matter, a single fragment with

    1010 NAME kpreston\r\n1018 INFO "Welcome to PvPGN BnetD 1.5.0!"\r\n1018 INFO "Type /help for a list of commands."\r\n

    If you're expecting to deal with 3 separate lines like

    1010 NAME kpreston\r\n
    1018 INFO "Welcome to PvPGN BnetD 1.5.0!"\r\n
    1018 INFO "Type /help for a list of commands."\r\n

    then you need to have a function which receives data, and returns lines when one (or more) newline pairs are found (and keep the rest of the message safe for next time).
    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.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    Quote Originally Posted by Salem View Post
    But there's nothing to say that 3 message fragments might be

    1010 NAME kpreston\r\n1018 INFO
    "Welcome to PvPGN BnetD 1.5.0!"\r
    \n1018 INFO "Type /help for a list of commands."\r\n

    Or for that matter, a single fragment with

    1010 NAME kpreston\r\n1018 INFO "Welcome to PvPGN BnetD 1.5.0!"\r\n1018 INFO "Type /help for a list of commands."\r\n

    If you're expecting to deal with 3 separate lines like

    1010 NAME kpreston\r\n
    1018 INFO "Welcome to PvPGN BnetD 1.5.0!"\r\n
    1018 INFO "Type /help for a list of commands."\r\n

    then you need to have a function which receives data, and returns lines when one (or more) newline pairs are found (and keep the rest of the message safe for next time).
    All three examples are possible.

  9. #9
    Banned master5001's Avatar
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    Speed is an important consideration to make however what good is speed going to do when you keep timing out? How important is fast when you swiftly lose connection? You have to take a more balanced approach my friend.

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    I've got it. The above example I typed up quickly in notepad actually compiled and worked perfectly.

    Bonus question!

    Code:
    token += 11;
    This is my half-assed attempt at string manipulation. I read an example that used it years ago. Why does it work? Is there a "better" way?
    Attached Files Attached Files
    • File Type: c xgn.c (3.0 KB, 119 views)

  11. #11
    Banned master5001's Avatar
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    You are skipping over the data inside the header. You are leaping over a constant size, so always double check documentation periodically to see if that constant ever changes.

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    Quote Originally Posted by master5001 View Post
    You are skipping over the data inside the header.
    You lost me.

  13. #13
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    You are skipping over some of the stuff that was received.

  14. #14
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    Quote Originally Posted by master5001 View Post
    You are skipping over some of the stuff that was received.
    Are you responding to the token += 11 thing?

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    Yep.

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