Monit restarts NGINX every 2 Minutes

Good morning,
In /var/log/monit.log i have the following Lines:

Code:

[2025-12-11T08:29:24+0000] error    : 'nginx' failed protocol test [DEFAULT] at [localhost]:443 [TCP/IP] -- Connection refused
[2025-12-11T08:29:24+0000] info     : 'nginx' trying to restart
[2025-12-11T08:29:24+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T08:29:24+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'
[2025-12-11T08:31:24+0000] error    : 'nginx' failed protocol test [DEFAULT] at [localhost]:443 [TCP/IP] -- Connection refused
[2025-12-11T08:31:24+0000] info     : 'nginx' trying to restart
[2025-12-11T08:31:24+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T08:31:25+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'
[2025-12-11T08:33:25+0000] error    : 'nginx' failed protocol test [DEFAULT] at [localhost]:443 [TCP/IP] -- Connection refused
[2025-12-11T08:33:25+0000] info     : 'nginx' trying to restart
[2025-12-11T08:33:25+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T08:33:26+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'
[2025-12-11T08:35:26+0000] error    : 'nginx' failed protocol test [DEFAULT] at [localhost]:443 [TCP/IP] -- Connection refused
[2025-12-11T08:35:26+0000] info     : 'nginx' trying to restart
[2025-12-11T08:35:26+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T08:35:27+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'
[2025-12-11T08:37:27+0000] error    : 'nginx' failed protocol test [DEFAULT] at [localhost]:443 [TCP/IP] -- Connection refused
[2025-12-11T08:37:27+0000] info     : 'nginx' trying to restart
[2025-12-11T08:37:27+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T08:37:27+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'

What do I need to do to successfully test [localhost]:443?

 

This is my Monit config for Nginx, which works like a charm

Code:

check process nginx with pidfile /var/run/nginx.pid
        group nginx
        start program = "/usr/bin/systemctl start nginx" with timeout 60 seconds
        stop program = "/usr/bin/systemctl stop nginx"
        if failed port 80 protocol http then restart
        if failed port 443 protocol https then restart
        if 5 restarts within 5 cycles then timeout
        depend nginx_bin

check file nginx_bin with path /usr/sbin/nginx
        group nginx
        include /etc/monit/templates/rootbin

 

Thanks for your reply.
I using the default configuration, that was created by the installer script:
/etc/monit/conf-enabled/nginx

Code:

check process nginx with pidfile /var/run/nginx.pid
    group nginx
    start program = "/usr/bin/systemctl start nginx" with timeout 60 seconds
    stop program = "/usr/bin/systemctl stop nginx"
    if failed port 80 protocol http then restart
    if failed port 443 then restart
    if 5 restarts within 5 cycles then timeout
    depend nginx_bin
 
check file nginx_bin with path /usr/sbin/nginx
    group nginx
    include /etc/monit/templates/rootbin

If i adding
if failed port 443 protocol https then restart:

Code:

check process nginx with pidfile /var/run/nginx.pid
    group nginx
    start program = "/usr/bin/systemctl start nginx" with timeout 60 seconds
    stop program = "/usr/bin/systemctl stop nginx"
    if failed port 80 protocol http then restart
    if failed port 443 protocol https then restart
    if 5 restarts within 5 cycles then timeout
    depend nginx_bin
 
check file nginx_bin with path /usr/sbin/nginx
    group nginx
    include /etc/monit/templates/rootbin

The Problem still exists, NGINX restarts every 2 Minutes:

Code:

[2025-12-11T12:58:46+0000] error    : 'nginx' failed protocol test [HTTP] at [localhost]:443 [TCP/IP TLS] -- Connection refused
[2025-12-11T12:58:46+0000] info     : 'nginx' trying to restart
[2025-12-11T12:58:46+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T12:58:46+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'
[2025-12-11T13:00:46+0000] error    : 'nginx' failed protocol test [HTTP] at [localhost]:443 [TCP/IP TLS] -- Connection refused
[2025-12-11T13:00:46+0000] info     : 'nginx' trying to restart
[2025-12-11T13:00:46+0000] info     : 'nginx' stop: '/usr/bin/systemctl stop nginx'
[2025-12-11T13:00:47+0000] info     : 'nginx' start: '/usr/bin/systemctl start nginx'

 

Must be the issue.
The original config from the installer works fine too here.

 

I have just checked all websites. SSL is active everywhere. It is either a self-signed certificate (created by ISPconfig) or a LetsEncrypt certificate. In addition, SSL runs on port 443 for all websites.

 

It is obvious that monit cannot connect to locahost on port 443.
In the logs "Connection refused" says it all.
Question is why monit cannot connect. My guess is some kind of firewall issue.
Try it with a simple telnet from te command line and see what happens than

Code:

telnet localhost 443

 

have any of the nginx system files been updated?, if monit is also monitoring the checksum of the nginx files and they've been changed then that could fail as well.

maybe (assuming you're sure everything has been safely updated and no files have been maliciously altered) try
rkhunter --propupd
systemctl reload monit

and then check the monit status page for nginx, you may need to select the bin file and select 'enable monitoring' again

 

I found the problem. NGINX was only listening on port 443 for the configured domains.

To make NGINX listen on *:443, I had to configure the IP * for one website.

Without this setting, ISPconfig does not create the following configurations in the NGINX configuration:
listen *:443 ssl http2;
listen [::]:443 ssl http2;

 

as of many many years

As is ispconfig's default config also.