node.js - Using port 80 with Node on Digital Ocean Error: listen EADDRINUSE -

i trying run simplest of node servers on digital ocean server. developed , tested code using port 8080 without problems. however, want use port 80 not need specify port when navigating ip address of server (so default).

when change port 80 , run app sudo error: listen eaddrinuse when not have other applications running on server (at all). there way clear port 80 use?

i checked here how fix error: listen eaddrinuse while using nodejs? none of suggestions worked. program on server.

there no other processes in code listening on port. there no app running on server @ not understand how port in use. help

edit. here running netstat returns:

active internet connections (w/o servers) proto recv-q send-q local address           foreign address         state       tcp        0      0 192.241.228.76:ssh      mobile-166-137-17:62351 established tcp        0      0 192.241.228.76:ssh      199-241-200-214.p:41732 established tcp        0      0 192.241.228.76:9090     199-241-200-214.p:38480 established tcp        0      0 192.241.228.76:ssh      mobile-166-137-17:45329 established tcp        0      0 192.241.228.76:ssh      199-241-200-214.p:47247 established tcp        0    308 192.241.228.76:ssh      199-241-200-214.p:44441 established active unix domain sockets (w/o servers) proto refcnt flags       type       state         i-node   path unix  8      [ ]         dgram                    7710     /dev/log unix  3      [ ]         stream     connected     1113212   unix  3      [ ]         stream     connected     7405     @/com/ubuntu/upstart unix  3      [ ]         stream     connected     7394      unix  3      [ ]         stream     connected     1113211   unix  2      [ ]         dgram                    9255      unix  3      [ ]         stream     connected     7681      unix  3      [ ]         stream     connected     7617     /var/run/dbus/system_bus_socket unix  3      [ ]         stream     connected     1113404   unix  3      [ ]         stream     connected     1113682   unix  2      [ ]         dgram                    1113070   unix  2      [ ]         dgram                    1113287   unix  3      [ ]         stream     connected     1113683  /var/run/dbus/system_bus_socket unix  3      [ ]         stream     connected     1113675   unix  3      [ ]         stream     connected     7601      unix  3      [ ]         stream     connected     7602      unix  3      [ ]         stream     connected     7631     @/com/ubuntu/upstart unix  3      [ ]         stream     connected     1114471   unix  2      [ ]         dgram                    1111881   unix  3      [ ]         stream     connected     1113411   unix  3      [ ]         stream     connected     1113219  /var/run/dbus/system_bus_socket unix  3      [ ]         stream     connected     1113218   unix  3      [ ]         stream     connected     1112008   unix  3      [ ]         stream     connected     8858     @/com/ubuntu/upstart unix  3      [ ]         dgram                    7439      unix  3      [ ]         stream     connected     7682     /var/run/dbus/system_bus_socket unix  3      [ ]         stream     connected     8836      unix  3      [ ]         stream     connected     1114472   unix  3      [ ]         dgram                    7438      unix  3      [ ]         stream     connected     1113412  /var/run/dbus/system_bus_socket unix  3      [ ]         stream     connected     1113676   unix  2      [ ]         dgram                    1113552   unix  3      [ ]         stream     connected     1113405   unix  3      [ ]         stream     connected     7616      unix  3      [ ]         stream     connected     7594      unix  3      [ ]         stream     connected     1112002   unix  2      [ ]         dgram                    1114349   unix  3      [ ]         stream     connected     1112001   unix  3      [ ]         stream     connected     1112009  /var/run/dbus/system_bus_socket 

and here running ps -ax returns

 pid tty      stat   time command     1 ?        ss     0:05 /sbin/init     2 ?        s      0:00 [kthreadd]     3 ?        s      0:01 [ksoftirqd/0]     5 ?        s<     0:00 [kworker/0:0h]     7 ?        s      0:09 [rcu_sched]     8 ?        s      0:00 [rcu_bh]     9 ?        s      0:00 [migration/0]    10 ?        s      0:14 [watchdog/0]    11 ?        s<     0:00 [khelper]    12 ?        s      0:00 [kdevtmpfs]    13 ?        s<     0:00 [netns]    14 ?        s<     0:00 [writeback]    15 ?        s<     0:00 [kintegrityd]    16 ?        s<     0:00 [bioset]    17 ?        s<     0:00 [kworker/u3:0]    18 ?        s<     0:00 [kblockd]    19 ?        s<     0:00 [ata_sff]    20 ?        s      0:00 [khubd]    21 ?        s<     0:00 [md]    22 ?        s<     0:00 [devfreq_wq]    23 ?        s      2:16 [kworker/0:1]    24 ?        s      0:00 [khungtaskd]    25 ?        s      0:00 [kswapd0]    26 ?        sn     0:00 [ksmd]    27 ?        s      0:00 [fsnotify_mark]    28 ?        s      0:00 [ecryptfs-kthrea]    29 ?        s<     0:00 [crypto]    41 ?        s<     0:00 [kthrotld]    44 ?        s      0:00 [scsi_eh_0]    45 ?        s      0:00 [scsi_eh_1]    65 ?        s<     0:00 [deferwq]    66 ?        s<     0:00 [charger_manager]   119 ?        s      0:04 [jbd2/vda-8]   120 ?        s<     0:00 [ext4-rsv-conver]   254 ?        s      0:00 upstart-udev-bridge --daemon   259 ?        ss     0:00 /lib/systemd/systemd-udevd --daemon   321 ?        ss     0:00 dbus-daemon --system --fork   351 ?        ss     0:00 /lib/systemd/systemd-logind   354 ?        ssl    0:19 rsyslogd   363 ?        s      0:00 upstart-file-bridge --daemon   367 ?        s<     0:00 [kpsmoused]   371 ?        s      0:00 [kworker/0:2]   463 ?        s<     0:00 [kvm-irqfd-clean]   730 ?        s      0:00 upstart-socket-bridge --daemon   773 tty4     ss+    0:00 /sbin/getty -8 38400 tty4   777 tty5     ss+    0:00 /sbin/getty -8 38400 tty5   783 tty2     ss+    0:00 /sbin/getty -8 38400 tty2   784 tty3     ss+    0:00 /sbin/getty -8 38400 tty3   786 tty6     ss+    0:00 /sbin/getty -8 38400 tty6   811 ?        ss     0:12 /usr/sbin/sshd -d   817 ?        ss     0:00 acpid -c /etc/acpi/events -s /var/run/acpid.socket   819 ?        ss     0:02 cron   821 ?        ss     0:00 atd   898 tty1     ss+    0:00 /sbin/getty -8 38400 tty1   933 ?        s<     0:00 [kworker/u3:1]   938 ?        s      0:00 [kauditd] 24995 ?        s      0:00 [kworker/u2:1] 29226 ?        s      0:07 [kworker/u2:0] 29542 ?        ss     0:00 screen 29543 pts/2    ss+    0:00 /bin/bash 30826 pts/6    ss+    0:00 -bash 30892 ?        sl     0:00 nodejs index.js 30962 pts/1    r+     0:00 ps -ax 

i got error. seems node throw error, if address isn't in use, if fails attach process port reason.

in case (a digital ocean droplet) attaching port 80 required sudo.