WinXP UVNC server file transfer extremely slow

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This has been bothering me for a while but I never had the time to isolate the problem.

Client: WinXP, Win10 - UltraVNC 1.2.1.2 100Mbps LAN
Server: WinXP - UltraVNC 1.2.1.2 GigaBit LAN

When I run UltraVNC server as a service, file transfers are extremely slow and choppy (transfer some, then stuck, transfer some more, then stuck, etc.) This happens with Client on WinXP and Client on Win10

I tested file transfers using windows file sharing and I could send/receive files at full LAN speeds.

This got me thinking it wasn't a network problem, but a problem with UltraVNC server running on this box.

During one of the slow file transfers, I went onto the server machine and brought up the properties for UltraVNC server using the taskbar icon. The file transfer immediately went very fast and smooth. I was able to repeat this multiple times. If I closed the properties window, back to slow choppy file transfers.

I decided to uninstall UltraVNC server as a service and just put it in the startup folder and run as a regular process.

Now my transfers are fast all the time.

It seems in my original config running as a service, UltraVNC server is not getting enough time slices to process the file transfer, but when I bring up the properties page, it gets all the time slices it needs.

Any idea what might be the root cause of the problem?

PS I did try going into WinXP performance config and change the optimization from Programs to Background Services (then rebooted) but it didn't seem to make any difference. Still had to bring up the properties windows to get transfers to go fast.

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This problem was resolved in test build 1.2.1.6 available here:
http://forum.ultravnc.info/viewtopic.ph ... 13#p102032