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I need a simple utility that allow me to check if a PC, attached to a local network, is able to reach a specified address:port using specified protocol like TCP or UDP

Machine's OS I will use to do the check is Windows XP.

Can you help me, please?

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2 Answers 2

up vote 6 down vote accepted

Use simply telnet:

telnet hostname port

If you get a connection, something replies on that port.

If you get an error message, no program is listening on that port, or the hostname is invalid:

Connecting To hostname...Could not open connection to the 
host, on port <port>: Connect failed
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+1, telnet or the allmighty netcat (nc), but you have to grab that from "somewhere", so telnet is just fine. –  akira Apr 8 '10 at 12:01
@snark which protocol is used to do this test? TCP, UDP or other? –  Drake Apr 8 '10 at 12:28
TCP is used, as telnet establishes a connection. UDP is connectionless so you cannot tell if someone is listening or not. –  Snark Apr 8 '10 at 13:08
thanks. So there is no way to use a tool to check if UDP is allowed in output on a certain port? Only using the desired application and see it is working? –  Drake Apr 8 '10 at 15:40

nmap should be able to handle this.

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