map $remote_addr $ip_version {
    ~:      "IPv6";
    default "IPv4";
}

server {
    listen 80;
    listen [::]:80;

    location / {
        default_type text/plain;

        return 200 "
You are connected to: http://$host/

==============================
  Connection Information
==============================
IP Version               : $ip_version
Source IP Address        : $remote_addr
Destination IP Address   : $server_addr
Source Port              : $remote_port
Destination Port         : $server_port
HTTP Version             : $server_protocol
Host Header              : $http_host
User-Agent Header        : $http_user_agent
";
    }
}