It does not seem to affect lighttpd. Journalctl did output following when it happened last time:
syys 12 22:03:41 sipuli dhclient[3111]: PRC: Renewing lease on wlp2s0b1. syys 12 22:03:41 sipuli dhclient[3111]: XMT: Renew on wlp2s0b1, interval 9430ms. syys 12 22:03:41 sipuli dhclient[3111]: RCV: Reply message on wlp2s0b1 from fe80::924e:2bff:fe5b:9c6e. syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3234] valid_lft 7200 syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3235] preferred_lft 3600 syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3236] address 2001:14bb:170:83bf::6 syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3236] nameserver 'fe80::924e:2bff:fe5b:9c6e' syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3237] dhcp6 (wlp2s0b1): state changed bound -> boun syys 12 22:03:41 sipuli dbus[2491]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' uni syys 12 22:03:41 sipuli systemd[1]: Starting Network Manager Script Dispatcher Service... syys 12 22:03:41 sipuli dbus[2491]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher' syys 12 22:03:41 sipuli systemd[1]: Started Network Manager Script Dispatcher Service. syys 12 22:03:41 sipuli nm-dispatcher[23149]: req:1 'dhcp6-change' [wlp2s0b1]: new request (1 scripts) syys 12 22:03:41 sipuli nm-dispatcher[23149]: req:1 'dhcp6-change' [wlp2s0b1]: start running ordered scripts... syys 12 22:17:01 sipuli CRON[23324]: pam_unix(cron:session): session opened for user root by (uid=0) syys 12 22:17:01 sipuli CRON[23325]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) syys 12 22:17:01 sipuli CRON[23324]: pam_unix(cron:session): session closed for user root syys 12 22:17:33 sipuli unix_chkpwd[23333]: password check failed for user (il) syys 12 22:17:33 sipuli compiz[3410]: pam_unix(unity:auth): authentication failure; logname= uid=1000 euid=1000 tty= syys 12 22:17:39 sipuli compiz[3410]: pam_ecryptfs: seteuid error syys 12 22:17:39 sipuli compiz[3410]: gkr-pam: unlocked login keyring syys 12 22:18:59 sipuli systemd[1]: Started CUPS Scheduler. syys 12 22:19:12 sipuli dbus[2491]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='d syys 12 22:19:12 sipuli systemd[1]: Starting Hostname Service... syys 12 22:19:13 sipuli dbus[2491]: [system] Successfully activated service 'org.freedesktop.hostname1' syys 12 22:19:13 sipuli systemd[1]: Started Hostname Service. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to cups in Ubuntu. https://bugs.launchpad.net/bugs/1622707 Title: CUPS Web UI stops responding after a while Status in cups package in Ubuntu: New Bug description: CUPS Web administration UI available at localhost:631 stops responding after a while. Initially it works fine, but after it has been running for a moment it just shows the "Connection refused" message of the browser. The printing system keeps running otherwise. This is a clean install of Ubuntu. I have installed Seafile from PPA but I don't think it has anything to do with this. I am unable to find anything relevant from journalctl nor CUPS logs. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: cups 2.1.3-4 ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16 Uname: Linux 4.4.0-36-generic x86_64 ApportVersion: 2.20.1-0ubuntu2.1 Architecture: amd64 CupsErrorLog: CurrentDesktop: Unity Date: Mon Sep 12 21:10:33 2016 EcryptfsInUse: Yes InstallationDate: Installed on 2016-09-12 (0 days ago) InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719) Lpstat: Error: command ['lpstat', '-v'] failed with exit code 1: lpstat: No destinations added. MachineType: Dell Inc. Latitude E6320 Papersize: a4 ProcEnviron: LANGUAGE=fi PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=fi_FI.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-36-generic.efi.signed root=UUID=0b75be02-897e-4a0b-9ff6-441512bb7493 ro quiet splash vt.handoff=7 SourcePackage: cups UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 11/14/2013 dmi.bios.vendor: Dell Inc. dmi.bios.version: A19 dmi.board.name: 05VMY6 dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 9 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvrA19:bd11/14/2013:svnDellInc.:pnLatitudeE6320:pvr01:rvnDellInc.:rn05VMY6:rvrA00:cvnDellInc.:ct9:cvr: dmi.product.name: Latitude E6320 dmi.product.version: 01 dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cups/+bug/1622707/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp