Server programs which are accessed from the network must be associated to a certain network port. Thus, several different server programs can be run on a single machine. For every service there are standard ports on which these are usually provided. For instance, a web server is ordinarily run on port number 80; the MySQL database server uses port 3306. MAMP PRO allows you to change the ports the servers should listen to. By default, MAMP uses non-standard ports. The MAMP servers can be thereby operated in addition to already installed web and MySQL servers. Should the ports 8888 and 8889 be already used by another application, you will need to change these values accordingly.