internet port filtering

Any network software will take the usage of "Port" if it is based on the TCP/IP communication, such as the software for stock exchanging, FTP, E-mail transmitting and so on, all of them have their own opened ports. Therefore, it will be very effective to block the Internet accessing through the blocking of these "Ports".
Even if the ports for many software are defined by their developers, the user should not be worried about being changed of his/her own "opened port" by those software. This is because that once the "opened port" is changed, the client port of those software must be changed accordingly. It seems not realistic from the view of the market.
If the he/she is familiar with the IP packages, the user may analyze the port with the "IP Package Analyzing Tool" equipped by this system.