Normally when you login to Central Management Console, no port number is specified, but just the hostname, or IP address. This will default to port 6400 (protocol TCP for firewall purpose)
However, it is possible to specify hostname and port number as shown below. In other word, it is possible to install multiple instance of CMC server, which points to different repository database, or single database with multiple database schema/username (simplified database management) for non-PROD or research purpose.
In project development, keeping the cost down by hiring less DBA, VMware admin, Windows admin, UNIX admin is one of the main saving in human resource budgeting.
Although virtual server (VMware, Oracle VM) often be used for multiple non-PROD environment, they are indirectly require additional maintenance. For example, 6 environment of DEV1, DEV2, QA1, QA2, UAT1, UAT2, there will be 6 Unix to patch, 6 times Unix user management, 6 databases, 6 Crystal Reports, etc.
So if it is not necessary, keep it simple, especially for databases where there are a lot of developers, and users has no clue about its design, maintenance, recovery, tuning, patching, known bugs, etc