Configure the ports of Firewall or security software to allow sharing

How can I determine which ports are active

IM Ports

Microsoft Applications' Ports and Protocols

Popular Port #

Ports for vpn

SBS Ports

Well-Know Ports

How can I determine which ports are active

Symptom: you have a server providing HTTP and FTP to the Internet users and the users are able to access the HTTP but not FTP.

Resolution: Run netstat -a command that will shows all active ports.

Popular Port #

FTP: 21

Telnet: 23

SMTP: 25

HTTP: 80

POP: 110

HTTPS: 443

VPN: uses TCP Port 1723, IP Protocol 47 (GRE); L2TP: UDP Port 1701; IPSec: UDP 500, Pass  protocol 50 and 51.