Telnet cmd to check open ports

[siki85]

Hi mates,

My doubt is about using telnet to see open ports remotely.

For example, there are sometimes when you use telnet x.x.x.x (port) to check open ports right ?
So, if I'm checking DNS (port 53) to see if it is running, and I don't receive responses it means the port is closed ?
because I did the same with a public DNS (8.8.8.8) and I get a prompt when using cmd.

Thanks for any advice....

 

[Noway2]

If you attempt to telnet to a port and do not get a response, as in the connection times out, it MAY mean that the port is closed. Telnet is used to establish a fairly raw and generic connection to a service. It isn't a really good tool for determining if ports are open, for that the nmap utility would work much better. In order for a port to be open, it has to both have a process listening on that port and have appropriate firewall settings on any devices upstream.

 

[mattKnight]

Don't forget that (mostly) DNS uses UDP, and telnet will try to open a TCP connection!

Some DNS servers will respond on TCP/53 (like 8.8.8.8), but not all!



Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[siki85]

Ok.

Thanks for your clear responses.