Socket recv call freezes thread for approx. 5 seconds

I've a client server architecture implemented in C++ with blocking sockets under Windows 7. Everything is running well up to a certain level of load. If there are a couple of clients (e.g. > 4) receiving or sending megabytes of data, sometimes the communication with one client freezes for approximately 5 seconds. All other clients are working as expected in that case.

The buffer size is 8192 bytes and logging on the server side reads as follows:

TimeStamp (s.ms) - received bytes

…

1299514524.618 - 8192

1299514524.618 - 8192

1299514524.618 - 0004

1299514529.641 - 8192

1299514529.641 - 3744

1299514529.641 - 1460

1299514529.641 - 1460

1299514529.641 - 8192

…

It seems that only 4 bytes can be read withi开发者_开发知识库n that 5 seconds. Furthermore I found out that the freezing time is always arounds that 5 seconds - never 4 or less and never 6 or more...

Any ideas?

Best regards

Michael

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This is a Windows bug.

KB 2020447 - Socket communication using the loopback address will intermittently encounter a five second delay

A Hotfix is available in

KB 2861819 - Data transfer stops for five seconds in a Windows Socket-based application in Windows 7 and Windows Server 2008 R2

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I've had this problem in situations of high load: the last packet of TCP data sometimes reached before the second to last, as the default stack is not defined for package sorting, this disorder caused in receiving similar result to what you describe.

The solution adopted was: load distribution in more servers