location / {
    proxy_http_version 1.1;
    proxy_set_header Connection "keep-alive";
    proxy_set_header Upgrade $http_upgrade; 
    proxy_set_header Connection "upgrade"; 
    proxy_set_header X-Real-IP $remote_addr;
    if (!-f $request_filename) {
        proxy_pass http://127.0.0.1:9508;
    }
}