Normally, It depends on which services are running the server.
Default ports which can be used by Plesk are listed below:
20 ftp-data
21 ftp
22 ssh
25 smtp
53 dns (TCP and UDP)
80 http (web server and Plesk updater)
106 poppassd (for localhost only)
110 pop3
113 auth
143 imap
443 https
465 smtps
587 mail message submission
990 ftps
993 imaps
995 pop3s
3306 mysql
5224 (outgoing connections only) plesk-license-update
5432 postgres
8443 plesk-https
8880 plesk-http
9080 tomcat
Not all ports are required but some are optional.
