Specify the port number for accepting LDAP connections. The standard port for LDAP communication is 389, although other ports can be used. For example, if you must be able to start the server as a regular user, use an unprivileged port, by default 1389. Port numbers less than 1024 require privileged access. If you use a port number that is less than 1024, certain LDAP commands must be run as root.
Specify the port number for accepting SSL-based connections. The standard port for SSL-based LDAP (LDAPS) communication is 636, although other ports can be used, such as the default 1636 when running as a regular user. For example, an unprivileged port might be required so that the server can be started as a regular user.
If you specify a non-privileged port and a server instance is installed on a system to which other users have access, you might expose the port to a hijack risk by another application. In other words, another application can bind to the same address/port pair. The rogue application might then be able to process requests that are intended for the server. The application could also be used to capture passwords used in the authentication process, to alter client requests or server responses, or to produce a denial of service attack.
Both Directory Server and Directory Proxy Server allow you to restrict the list of IP addresses on which the server listens. Directory Server has configuration attributes nsslapd-listenhost and nsslapd-securelistenhost. Directory Proxy Server has listen-address properties on ldap-listener and ldaps-listener configuration objects. When you specify the list of interfaces on which to listen, other programs are prevented from using the same port numbers as your server.