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I'm making a simple mmorpg server with IOCP. I implemented a simple movement function so I tested with dummy clients(also IOCP). Everything works fine only when few clients are connected. After around 500~1000 clients are connected, some dummy clients occasionally read weird data. I checked that server sends data as I expected but when it comes to dummy clients reading them, they read random data.

My guess is that it could be related to operation system's recv buffer being overflowed but I'm only guessing right now... I have no idea how to check them.

Any suggestion would be very thankful!

Len Holgate
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Jeongmin Heo
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1 Answers1

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The problem with too many WSASends doesn't usually manifest as corrupted data; that's more likely to be a bug in your code. Perhaps your problem is caused by you failing to manage the lifetime of the buffer that is being used to send data correctly? It needs to stay stable until you get the completion for the WSASend call. If you were reusing it sooner than that then you would corrupt the data being sent.

The reason this may show up when you have lots of WSASends outstanding to lots of clients is that the send operations may be taking longer to complete and so make it more likely that your bug will be hit...

It doesn't matter how many WSASends you issue as long as your clients are able to receive the data as fast as you can send it. As soon as you are sending faster than they can receive then there will be problems. I address these problems in this answer.

Len Holgate
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