/usr/lib/firewalld/services/ Current File: //usr/lib/firewalld/services/xdmcp.xml

<?xml version="1.0" encoding="utf-8"?>
<service>
  <short>XDMCP</short>
  <description>The X Display Manager Control Protocol (XDMCP) allows to remotely log in to an X desktop environment from any X Window System compatible client.</description>
  <port port="177" protocol="tcp"/>
  <port port="177" protocol="udp"/>
</service>