A network "port" may sound like a physical connection of some kind, like the USB ports on the back (or front or side) of your computer. In network terminology, though, a port is most often a logical or virtual concept, part of a network transport protocol (TCP/IP, for example, or UDP). In this sense, a port is a logical destination on a specific host that is identified with some particular service or listener. Port 21, for example, is often used for FTP servers.
Ports are most often significant to FileMaker administrators who administer or otherwise encounter firewalls. Many firewalls do port-based blocking or filtering of traffic. If traffic to or from a particular port is not permitted across a firewall, services may be disrupted or blocked. For example, if port 21 is blocked on a firewall, an FTP server behind that firewall will be unreachable. If port 5003 is blocked on a firewall, a FileMaker server behind the firewall will be unreachable.
For an extensive listing of port numbers, see the list maintained by IANA at http://www.iana.org/assignments/port-numbers. Some of the FileMaker network ports are registered whereas others are not, though this has little practical significance for FileMaker administrators.
: FileMaker Specifications
FileMaker 8 Product Line
Specifications and Storage Limits
Field Types and Import/Export Formats
: Calculation Functions
Working with Calculations Primer
: Custom Functions
Custom Functions Primer
Useful Custom Functions
: Script Steps
Script Step Reference
: Quick Reference
FileMaker Error Codes
FileMaker Keyboard Shortcuts
FileMaker Network Ports
FileMaker Server Command Line Reference
FileMaker XML Reference
: Other Resources
Where to Go for More Information