Menu
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 within 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
606
recv(IPC, Buffer, int n) is a blocking call, that is, if data is available it writes it to the buffer and immediately returns true, and if no data is available it waits for at least n seconds to receive any data.
If successful, recv() returns the length of the message or datagram in bytes. The value 0 indicates the connection is closed.
The recv() function receives a message from a socket. The recv() call can be used on a connection mode socket or a bound, connectionless socket. If no messages are available at the socket, the recv() call waits for a message to arrive unless the socket is nonblocking.
Return value If no error occurs, recv returns the number of bytes received and the buffer pointed to by the buf parameter will contain this data received. If the connection has been gracefully closed, the return value is zero.
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
73
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
