README.md

Swap out the two URLs (first is source, second is target) then run with curl:

curl -X POST -d @pingback.xml http://example.com/xmlrpc

pingback.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<methodCall>
<methodName>pingback.ping</methodName>
<params>
 <param>
  <value>
   <string>http://indiewebcamp.com/comment</string>
  </value>
 </param>
 <param>
  <value>
   <string>http://aaronparecki.com/replies/2013/03/19/1/indiewebcamp</string>
  </value>
 </param>
</params>
</methodCall>

IIRC faultCode 0 means it worked.

I checked and the other person still didn't receive a pingback, so, I convinced them to install the Webmention plugin instead 😊
Thanks for this gist though, @aaronpk!