Here you find some of the basic communication ports used by Citrix Xenapp/XenDesktop:

ICA Protocol 1494
ICA Protocol with Session Reliability 2598
IMA Communications 2512
Xenapp Advanced Console 2513
TCP Browsing 1604(udp)
XML Service Port (shared with IIS) t80
SSL Communications 443
License Management Console Port 8082
License Port 27000
User Desktop Shadowing (Remote assistance) 3389/135
SQL Server (also relevant) 1433

http://support.citrix.com/servlet/KbServlet/download/2389-102-654859/CitrixPorts_by_Port_1103.pdf For more ports, I refer to the Citrix website: