It has nothing to do with the specification. It is specific to a container. For example, when you deploy an ejb in glassfish, you can include glassfish-ejb-jar.xml in which you can bind the name to a remote ejb. For example:
Above, we are using someotherbean from another container and tying it to BeanB. To do so, we are using the remote server host and port in the jndi name. The host and port are specific to a container. So you have look at the specification of that container to learn what port and protocol to use.