XML-RPC call:

<?xml version="1.0"?>
<methodCall>
<methodName>mailkit.report.campaign</methodName>
<params>
  <param><value><int>client_id</int></value></param>
  <param><value><string>client_md5_hash_here</string></value></param>
  <param><value><int>campaign_id</int></value></param>
</params>
</methodCall>