QTcpSocket: extremely slow between winxp 64bit and 32bit

[preend]

Hi,

I am trying to make a simple computation system based on a distributed mode using QTcpSocket. The size of data stream transferred each time over QTcpSocket is easily up to a few hundred megabytes. In this case, network utilization rate might be critical.

The source code here came from modified fortuneclient/fortuneserver that they are able to transfer a large size of data (over 100MB). The maximum speed of the network (LAN) is 100Mbps. Some tested results listed below,

client (from) server (to) network utilization

winxp64bit linux 64bit 75-90% (75-90Mbps)
winxp64bit winxp64bit 75-85% (75-85Mbps)
winxp64bit winxp32bit 2-5% (2-5Mbps)

As above, the transfer speed between winxp64bit and winxp32bit is like 30 to 45 times slower. Using the same socket to transfer data back from the server to the client is even slower.
Can anyone give me some hints what causes the extremely slow connection between win64bit and 32bit?

Thanks a lot.
Preend.

[daemonna]

did you try xp_64 -> linux_32 ?? coz if you get also 75% that means there is something wrong with xp 32...

+ which ServicePack got that xp 32bit? did you look for known bugs on MS sites for that SP?

[JohannesMunk]

Maybe on your 32bit machine the TCP Window Size is set way too small?

Joh