UDP telnet client

[Red Squirrel]

Is there such thing as a UDP telnet client? I often use telnet to check if I can access a port. It helps me narrow down network troubleshooting, if I can connect, then i know it's not a firewall blocking and I know the server app is running.

Trying to troubleshoot NTP in windows. (NTP in windows = suxor) One of our DCs crapped out and it was set as the NTP server, so I'm trying to make the other DC the NTP server, but no luck so far. I want to see if it's even listening. I setup a linux box temporarly to act as NTP as I was able to have that up and running in like 10 minutes vs troubleshooting windows. If it was my choice we'd keep the linux box to act as NTP but they don't want anything to do with linux here.

 

[MrChad]

You could try TCPView. You certainly do seem to have a lot of problems with NTP.

 

[Red Squirrel]

That might help to see if the port is open and for cases where I have access to the server but I'd like to actually send data too. So for example I can send a NTP command to see what the response is, etc. Good for troubleshooting VPN as well, when I do not have physical access to the end server.

 

[her209]

The problem with UDP is that there is no three-way handshake that takes place like with TCP so there may be a process bound to the UDP port but may not respond because the packet is malformed according to the listening process and therefore does not respond.

You can check to see if something is listening on the desired UDP port by running "netstat -an" in Command Prompt. Also, why not use a wire sniffer like WireShark to see if the packets are being seen by the server?

Another option is if you wrote or found a program that would listen on a specified UDP port at runtime, and "reply" to any packet it received.

 

[Crusty]

netcat -u

 

[Nothinman]

The problem with UDP is that there is no three-way handshake that takes place like with TCP so there may be a process bound to the UDP port but may not respond because the packet is malformed according to the listening process and therefore does not respond.

You can check to see if something is listening on the desired UDP port by running "netstat -an" in Command Prompt. Also, why not use a wire sniffer like WireShark to see if the packets are being seen by the server?

Another option is if you wrote or found a program that would listen on a specified UDP port at runtime, and "reply" to any packet it received.

Netcat can do TCP and UDP. But it won't really help him test because he's still reliant on the NTP server replying or not.

Basically if it's a DC and there's no firewall NTP should be working, IIRC all DCs are NTP servers by default.