how can one connect using open ports...

hi all,
i know a little bit of all this www stuff....and keen on learning more....

in the process.. i got to know that.... all the connections are done through the different ports opened in a machine... there are some default ports for some services...like 80 for http: 23 for telnet etc....

now i was wondering that what if i want to connect to some machine using some other port which i have found open...can i directly telnet its ip specifying the port or is there any other way too...

how do i find and close open ports on my own machine..


i promise its just for the sake of learning ... no illegal stuff would be done...

Open ports are merely running services or programs on your machine that are actively "listening" for a specific signal coming across on a specific port. Many times we leave services running that aren't necessary without thinking about it. You can scan for these open ports using a port sniffer, or by using a free web-based one. There are several free security scans available on the internet that will scan for any open ports on your system. Here's one:

http://scan.sygatetech.com/

Here's a port sniffer if you'd like to do it yourself:

http://download.com.com/3000-2648-45...ml?tag=lst-0-1

Just to add to what roswell1329 said, those ports that are opened can be closed by shutting down the service that opened them. For instance, if you were running IIS 5.0 for a web server, by default, port 80 will be open on your machine. As you already know, port 80 is the standard for http traffic. If you stop IIS from running, port 80 is no longer open on your machine. Many times a default install of an operating system will leave certain ports open that do not really need to be open. As part of the process to secure your own machine, you should most certainly scan your entire machine for a listing of open ports, or use a tool such as FPort from Foundstone - http://www.foundstone.com - FPort will give you a list of ports that are open on your machine.