How to check if a port is open

[wurzel]

I'm having a few problems with network support. I'm using a VMWare application to clone a remote machine. In short, it uses ports 445 and 139, both of which are not accessible to my desktop pc, so the app doesn't work.
I ask the network guy to open the ports & he says he has done so but I still can't get it to work.
I tell him that I try to access specified ports via Telnet with no success.
He replies saying "Telnet doesnt use these ports, telnet has its own port, this proves nothing" . I might be missing something but I've used this method in the past to determine whether a port is open. Who's talking bollocks? Me or him?

[krytonsheep]

You can definitely telnet to a specific port, e.g.
telnet time-a.nist.gov 13

will telnet to port 13 and display the time.
So it should work.

[monkeyboy]

also if the telnet fails immediately you can deduce that a tcp rst was sent from the server or if configured an intermediate host. This can imply that the port isn't listening on the server. It requires specific config for the firewall to send a reset which is unlikely to be set.

If it times out then the packet was dropped or lost in transit. I presume ping works so there is not an underlying network issue. Unfortunately it is not possible to work out which hope drops the packet so you are at the mercy of the network guy in this case....

[wurzel]

Thanks, pretty much as I thought. Telnet has a default port but you can specify others. I have a feeling this network guy doesn't like the fact that I'm making work for him!

[RichardCranium]

I have a feeling this network guy doesn't like the fact that I'm making work for him!

I now know more than he does!

[NickFitz]

I tell him that I try to access specified ports via Telnet with no success.
He replies saying "Telnet doesnt use these ports, telnet has its own port, this proves nothing" .

FFS, what an utter tool

Tell him to start by reading this MS Knowledge Base article - it's just about simple enough for him to understand

Then tell your client that their "network guy" doesn't know a damn thing about networking, have him fired, and negotiate a doubling of your rate for taking on his responsibilities until a competent replacement is found.

[Platypus]

Check out these tools, they will help

http://www.foundstone.com/us/resourc.../superscan.htm
http://www.foundstone.com/us/resourc...desc/fport.htm
http://www.foundstone.com/us/resourc...esc/vision.htm

[bellymonster]

Could the Windows firewall be running on the client you are trying to clone?

[pmeswani]

Could the Windows firewall be running on the client you are trying to clone?

Not necessarily a Windows Firewall, but any software based Firewall will need to allow the port through.

[DogTown]

Seriously people, a service has to be running on a particular port!!! If you cant Telnet to it then guess what, maybe no Telnet service running there, it doesn't mean the port is closed!