how can i check the opened Ports in my Computer ?

Question

i use the BearShare ,,, but there is some trouble 2 get signed in for this prog.
they have told me that in Report Email

((If you are behind a corporate firewall, check with your System Administrator that the ports used by Bearshare for communication are not blocked for outgoing connection.
The port numbers are the following: Port 1863, port 80 and port 443.))
HOW CAN I CHECK THESE PORTS ??
should i call the ISP "internet service provider"
or , can i check it from my Computer ?
if yes ,, please HOW :'(
Much Thanx

Answer 1

get a port scanner, then check your own machine using 127.0.0.1 as the address. you can also check which ports are in use, by using netstat -a in a dos box.