Pinging a specific port

[msd]

Ok...not a real hardware geek. How can I tell whether an outside machine has access to a specific port on my machine.

In effect, I would like someone to be able to try and *ping* me on a specific port to verify that I can listen on that port.

Is there a tool to do that?

Thanks,
Matt

 

[shadowlight]

Well, all the versions of Windows come with a command line ping command, but since ping uses ICMP packets (which are different than TCP or UDP packets and don't really know anything about ports), you can't really "ping" a port.

You're probably looking for a TCP/IP application layer port scanner. Here's a couple you might try:
http://www.gfi.com/lannetscan/
http://www.famatech.com/

I've never used either of them though...

 

[Chris Tavares]

Ok...not a real hardware geek. How can I tell whether an outside machine has access to a specific port on my machine.

In effect, I would like someone to be able to try and *ping* me on a specific port to verify that I can listen on that port.

Is there a tool to do that?

Thanks,
Matt

If it's a windows box, bring up a command prompt (do win-menu run "cmd.exe" if on a NT class OS, "command.com" on Win 9x). Type "netstat /a" (without the quotes) and you'll get a list of all open & listening ports on your box.

This doesn't take any firewalls into account, since the netstat call is done inside the firewall; you'll need someone from outside to check if a particular port is accessible. If you trust them, you can use telnet to try to connect to a specific port. Just do "telnet <ip address> <port number>" and it'll try to connect to that port on that box.

 

[Vagabond]

Ok...not a real hardware geek. How can I tell whether an outside machine has access to a specific port on my machine.

In effect, I would like someone to be able to try and *ping* me on a specific port to verify that I can listen on that port.

Is there a tool to do that?

Thanks,
Matt

You're looking for a port scanner. I use nmap from http://www.insecure.org/nmap I haven't used the windows version, but the unix versions are top-rate. For best results, scan your pc twice. Once from the inside (on the computer itself, if you need to, otherwise another machine on your local network is preferred), and once from outside your local network. If your computer has an address like 192.168.x.x, then you likely have some protection from your firewall device, but you'll still want to find out the address of your firewall and have a friend scan that IP for open ports.

 

[msd]

Thanks to everyone who replied...this was all helpful. I found the sokution to my problem.

Thanks!

Matt