error taking snapshot:Net Exception

my server.log is flooded with these messages.
When printing with Repetier-Server (Raspberry Pi 4), there is also lots of layer-shift which is not, if I print via SD-Card directly on my Ultimaker2+
I think because of these messages, the CPU of the Raspy may have errors communicating with my Ultimaker2+ 
Could this be possible ?


  • That error only occurs if you have timelapse enabled and there is a problem reaching the configured webcam. So either disable timelapse or check webcam configuration.

    Layer shift is probably an other issue, also server has normally no influence on it. We just send the gcodes and printer would ensure that all moves are within limits the printer can handle meaning acceleration, speed etc are limited by printer or set from gcode you created and we just had send as requested. Layer shift has normally a physical reason:
    - especially if always away from end stop it is cross talk on end stop sensor causing a move to stop early.
    - random shift: Motor force exceeded either from hitting a plastic part, acceleration/speed to high loosing steps, overheat so motor disabled a short while.
    - moves outside limits, e.g. timelapse configured with making snapshots outside move area. Check settings or disable webcam.

    To see if communication had issues enable logging and watch afterwards for words like: timeout, resend
    These appear if communication goes wrong, but since send gcode is checksum protected wrong commands get corrected and not executed.
  • edited April 2023
    Thank you for your answer.
    Well, after days of experimenting I found the problem : Repetier-Server chocked after printing for a while and therefore skipped some commands, resulting in a layer shift. Enabling PingPong solved that problem.
    Shouldn´t  Repetier-Server have told me that he skipped some commands ?

  • On which commands did it choke? In 1.4.10 we have some extra solutions for slow commands not using ping-pong on them and even a treat timeout as long command. I think only way skipping could happen is with a long timeout on an unexpected slow command causing it to send more commands than server does buffer in recent command buffer. So in that version with these extra options for ping-pong off enabled (disabled by default) it should also not happen.
    But as said in first place it should not timeout so question is what was causing it so I can check if it is in the slow command list to improve on extending timeout in that case.
  • Well, I am not much into this but when using ping-pong every print, even the large ones are working perfectly. This looks like a solution for me. When switching ping-pong off, I have layer-shift nearly in every print, except I print directly from the SD-Card directly inserted in my Ultimaker2+ (not using RepetierServer).
  • Ok. In deed some printers can not handle parallel commands on usb correctly or some settings prevent it. Since it is not standard protocol it has sometimes it issues and then just using ping-pong is a good solution.
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