The config is rather simple as following. My test version is 1.7.2, a bit old. I can't upgrade to the latest one in our production for now. Anyway I think it should work in 1.7.2 because the document says proxy_protocol was introduced from 1.5.12.

http {
log_format combined '$proxy_protocol_addr - $remote_addr - $remote_user [$time_local] '
'"$request" $status $body_bytes_sent '
'"$http_referer" "$http_user_agent"';
...

server {
server_name www.abc.com;

listen 80;
listen 8181 proxy_protocol;

real_ip_header proxy_protocol;
real_ip_recursive on;
set_real_ip_from 192.168.1.0/24;

location / {
...
}
}
}