Solved

Winsock Recv/Send problem

Posted on 2009-07-13
3
1,599 Views
Last Modified: 2013-11-17
I've been having one hell of a problem with a program I'm making.  Basically, it's inter-process communication using sockets. I've done sockets for years, and just recently started running into this roadblock that I can't figure out.  I've gotten it to connect to the "server" (which is just another program running a bind on 127.0.0.1), but when we exchange information, I've used a set of MessageBox's to show me the data going between the two.  The MessageBox's hault program execution until user input, but from what I understand, messages are supposed to queue up, right? Anyways, this is what I'm getting (an example conversation):

-Connect to localhost-
server SEND: 0,CONNECTED
client RECV: 0,CONNECTED_TO_SERVER

client SEND: 1,COMMAND,1,ARGS,HERE
server RECV: 1,COMMAND,1,ARGS,HERE

server SEND: 2,FLUSH
client RECV: 2,FLUSHCTED_TO_SERVER

-----

You'll notice that my client is recv'ing but it almost looks like the buffer/recv queue I'm using isn't being flushed properly and it has remnants of previous packets in it.

Maybe it has something to do with my methodology? I'm using a while() loop on a non-blocking socket inside of a different thread in my GUI, and skipping past anything with a WSAEWOULDBLOCK error to recieve everything.  I hope the experts aren't laughing at me at this point :P

Here's the strange part...I'm doing EVERYTHING I can to zero this buffer out though..during every loop iteration, I set my buffer's 0 index to 0x00 like so:
recvBuff[0] = 0x00;
Which should set the string to null (just to make sure I'm not overwiting what I had)..from the server side, I used a MessageBox to show me what the server was sending, and it IS sending properly formatted packets, so I know the problem is on my client end...I even tried taking the recvBuff upon a successful recv call and doing a strncpy into a NEW buffer based on the size of data receieved like so:

lResult = recv(socket,recvBuff,512,0);
if(lResult > 0)
{
   strncpy(buff2,recvBuff,lResult);
  ..etc..
}

It probably has a whole lot to do with my loop, but I can't for the LIFE of me figure out why my buffer isn't clearing/why my socket recv data is all mashing together.

OH I FORGOT -- If I put a message box after the recv call showing the AMOUNT of data I received like so:

sprintf(buffer,"%i -- Number of bytes recvd",lResult);
MessageBox(0,buffer,"Recv",0);

Then it actually shows me the correct number AND parses correctly..but only if that message box is there. Is it a speed issue? What the hell is going on?? lol

Any help at all would be GREATLY appreciated...and if you can think of a better way to do winsock in C++ (I'm using MingW via Ultimate++), perhaps async sockets or something, PLEASE let me know. I'm about to smash my computer due to this lol :P

-Kevin
0
Comment
Question by:ProjectZIG
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 16

Expert Comment

by:George Tokas
ID: 24848619
With C++ Builder implementation is easy...
What compiler are you using??

George Tokas.
0
 

Author Comment

by:ProjectZIG
ID: 24850672
I'm using MinGW 32 and the Ultimate++ development environment.

http://www.ultimatepp.org/
0
 
LVL 27

Accepted Solution

by:
BigRat earned 500 total points
ID: 24961690
>> I'm using isn't being flushed properly and it has remnants of previous packets in it.

Which looks as if you're treating the socket connection as a packet sending/receiving system.

>> I've done sockets for years

Which suggests that you know that the system is a stream system.

Could you be a little more specific on what "client SEND: 1,COMMAND,1,ARGS,HERE" is?

In particular what exactly contitues a "packet"?
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Does the idea of dealing with bits scare or confuse you? Does it seem like a waste of time in an age where we all have terabytes of storage? If so, you're missing out on one of the core tools in every professional programmer's toolbox. Learn how to …
Since upgrading to Office 2013 or higher installing the Smart Indenter addin will fail. This article will explain how to install it so it will work regardless of the Office version installed.
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
In this fourth video of the Xpdf series, we discuss and demonstrate the PDFinfo utility, which retrieves the contents of a PDF's Info Dictionary, as well as some other information, including the page count. We show how to isolate the page count in a…

737 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question