Custom Zabbix server port instead of 10051

[olegus]

We need to use different port on Zabbix server as it is behind Cloudflare and 10051 is not an option. We opened port 2087 and map it to 10051 in server's docker-compose.yaml:

ports:
- 2087:10051​

Then on proxy side we changed environment variable for a port in proxy's docker-compose

   - ZBX_SERVER_HOST=example.com
   - ZBX_HOSTNAME=zabbix-proxy
   - ZBX_ACTIVE_ALLOW=true
   - ZBX_PROXYMODE=0
   - ZBX_CONFIGFREQUENCY=120​
   - ZBX_SERVER_PORT=2087

but according to logs it still tries to connect using 10051.
144:20240201:112143.134 Unable to connect to [example.com]:10051 [cannot connect to [[example.com]:10051]: [4] Interrupted system call]

What should we change on proxy side to use custom port to communicate with a server?

[olegus]

Looks like ZBX_SERVER_PORT var is ignored.
So we just set

- ZBX_SERVER_HOST=example.com:2087

but it does not help, proxy still cant talk to a server - here is what I see in logs:

144:20240201:121844.580 Message from example.com is missing header. Message ignored.

144:20240201:121844.580 cannot obtain configuration data from server at "example.com": cannot connect to [[example.com]:2087]: [4] Interrupted system call

Any idea where should I look next?

BTW, both server and proxy use alpine-6.4-latest image

[olegus]

Additional info:
Zabbix server URL is reachable rfom a proxy host
Zabbix server port 2087 is open , as shown by telnet:

telnet example.com 2087
Trying XX.XX.XX.XXX...
Connected to example.com.cdn.cloudflare.net.
Escape character is '^]'.

That's a verbose log from zabbix-sender, running from inside of a proxy container:

/var/lib/zabbix $ zabbix_sender -vv -z example.com -p 2087 -s "Monitored Host" -k mysql.queries -o 342.45
zabbix_sender [198]: DEBUG: In zbx_connect_to_server() [example.com]:2087 [timeout:60, connection timeout:3]
zabbix_sender [198]: DEBUG: In zbx_is_ip4() ip:'example.com'
zabbix_sender [198]: DEBUG: End of zbx_is_ip4():FAIL
zabbix_sender [198]: DEBUG: In zbx_is_ip6() ip:'example.com'
zabbix_sender [198]: DEBUG: End of zbx_is_ip6():FAIL
zabbix_sender [198]: Warning: Message from example.com is missing header. Message ignored.
zabbix_sender [198]: DEBUG: Unable to receive from [example.com]:2087 []
Sending failed.