I am writing software in a client/server environment and I am wanting to communicate with the server and all the other clients using TCP/IP via the VB Winsock control.

I have an app running (written by me in VB) on the server which accepts TCP/IP connections and data from several clients (also written in VB). The clients also accept data from the server (of course :)).

The problem is that most of the time it works without any problems. But sometimes 2 messages will be sent by the server in quick succession, and again usually this works fine and the client receives 2 distinct DataArrival events. Then every so often the 2 messages will be concatenated (not by my app, but by the OS I think) and the client only receives 1 DataArrival event with the data being both messages concatenated.

The only way to stop it doing this after the first time it happens is to restart the server (as in restart Win2K, not just my app). I have gone through my code and can not find anything wrong with it. I do a DoEvents before and after every Winsock.SendData but still the concatenation happens...sometimes.

I think that it only happens when I have more than one client connected to my server app, but I can not guarantee that.

Has anyone else experienced this type of problem, and if so were you able to fix it and how?

I know I could change the way it works and look for an end of message flag and split it at the client, but I would prefer not change my code that much.

Regards
Owain Williams

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Regards
Owain Williams

NOt going to help much, but a similar thing happens sometimes when using MSCOMM with RS232. The only way I have found to ensure that all is ok, is to test for string length's and data types coming in., part of the problem can be to do with noise on the line.

As far as I know, winsock sends an event when there is data in the buffer, and then you can use the BytesReceived property to check how much data there is. I am not surprized if windows collapses events (and it is more efficient too)

Marco