ssh - x11vnc Becomes Unresponsive After a While - Ask Ubuntu

lubuntu 16.04 lts running headless on banana pro, starting lemaker's official image. after imaging 32gb sd card, expanded system partition ~3.7gb fill card, booted first time , followed pseudocode:

do   # boot , ssh in   ssh bananapi@<ip_address>   bananapi    # initial setup on ssh   sudo su   bananapi   apt-get update   apt-get dist-upgrade -y                     # let wants   apt-get autoremove -y   nano /etc/sudoers                           # add bananapi in, copying root   nano /etc/update-manager/release-upgrades   # set desired option here   do-release-upgrade                          # let wants, including reboot while(do-release-upgrade did something)  apt-get install x11vnc -y x11vnc -storepasswd ******** /etc/x11vnc.pass nano /etc/rc.local 

/etc/rc.local includes line:

/usr/bin/x11vnc -noxrecord -shared -xkb -forever -auth /var/run/lightdm/root/:0 -display :0 -rfbauth /etc/x11vnc.pass -rfbport 5900 -bg -o /var/log/x11vnc.log 

when finishes rebooting, vnc clients on different windows , lubuntu machines can connect , control it. finish setting up, using combination of vnc/gui tweaks, ssh easy copy/paste, , sftp prefab scripts , source code build on pi, , reboot again.

when comes up, reconnect vnc client, , seems well. time later, notice vnc window unresponsive. not readonly, clock doesn't change. consistent between windows , linux clients. newly connected client shows same problem immediately: connection succeeds, shows outdated screenshot doesn't respond anything.

by time, having completed of setup, have auto-shutdown script (remember headless) when system switches battery power, can still shut down gracefully pulling ac plug. when comes up, vnc works again...for while. notice when vnc has failed, ssh , wifi access point still work, it's not complete system failure. vnc.

this problem same on 16.04 on original 14.04 image package upgrades, except lemaker hasn't released official 16.04 image yet.

any ideas?

i figured out! thread different vnc server on different machine , happenstance playing pi:

https://forum.ultravnc.net/viewtopic.php?f=3&t=31898

basically problem vnc server continues read display buffer no longer updated because video stuff has shut down. in thread above, that's because closed lid of laptop running server; in case of question, it's because default screen blanking time still there. once timed out, pi's graphics chip shut down, no longer updating buffer, , vnc server appeared have frozen.

why didn't come on vnc'ed mouse event, don't know, setting pi never turn screen off fixed dropout in first place.

(it's headless anyway, it's not i'm wasting power on screen doing this. maybe little bit on graphics chip, that's negligible in application.)