nginx version: nginx/1.22.1
5.10.160-legacy-rk35xx

server {
        include     /etc/nginx/listen.conf;
        server_name subdomain.domain;
        root        /var/www/html;

        index index.html;

        error_log   /var/log/nginx/subdomain-error.log error;
        access_log  /var/log/nginx/subdomain-access.log;
}

listen 81;

lsof -i :80
COMMAND   PID USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
nginx   76046 root   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76047   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76048   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76049   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76050   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76051   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76052   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76054   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)
nginx   76055   pi   40u  IPv4 1058016      0t0  TCP *:http (LISTEN)