Help - Dynamic TCP and UDP Ports

[dalerguy]

I'm running Timbuktu remote software and was told when using the (ICF) Internet Connection Firewall, the dynamic ports are blocked. So some services in the Timbuktu software are no working because they use these dynamic ports.

How does one list the TCP/UDP ports on a system (WinXP)? How do you know what ones are dynamic/static?

Is there a way to assign a service to a dynamic port?

Can I open a small range of dynamic ports, so the service will use a port from that range.


Any advice would be appreciated.

Thanks,

DalERguy

 

[JasonDeckard]

Use netstat -na from the command prompt to see a list of all active sockets.

When an application establishes a connection (that is, an outbound connection), the port the connection originates from is normally dynamic.

When an application offers a service by listening on a port, the application normally listens on the same port every time (for example, 23 for telnet or 80 for http). This is done so remote systems can find the service.

Although there are exceptions, a good rule of thumb is "inbound connections connect to static port numbers; outbound connections originate from dynamic port numbers".


Hope that helps,

Jason Deckard

 

[haviv512]

The statis/assigned port numbers are listed/updated at

http://www.iana.org/assignments/port-numbers

Well know protocols such as ftp, tftp, telnet all have specific port numbers. It is correct that normally the riginationg port is dynamic and the destination is static/prefixed. But it is also possible to use the same protocol, for example telnet, with an unassigned free port number instead of 23 for the destination telnet application. As long as the destination telnet application is aware that it has to listen on that port everything is OK. This tactic is sometimes used to add some basic security to telnet.