Can I use both LDAP and LDAPS on the same server?
You can do this. I was doing this when setting up my LDAP server cluster. To get everything stood up, we used port 389. Once we had a certificate, we did the install and opened up port 636. We can use both without issue. As the project matures all the various services that are consuming LDAP are being moved over to port 636. There is also a way to configure the listener on port 389 to use a certificate, but for us there's no need for that.