RHEL 7 GDM XDMCP Configuration

This is my first RHEL 7.4 server build. I have configured GDM to enable XDMCP in the /etc/gdm/custom.conf file in order to access this server via OpenText Exceed remotely. The issue is that udp is not listening on port 177 since lsof -PI :177 returns nothing. I have enabled gdm debugging but see no issues in the /var/log/messages or in the gdm logs in the /var/log/gdm directory. Perhaps I am missing some component here in the build but would have expected a message in the log of some sort. Thanks for any help can be provided here.