You can get stuck with your ssh session when your network is changing or when there’s a network disruption. You will face a lock leading to the unability to stop your session, even by doing a CTRL-C.

That’s why there’s some escape sequences you can use in that case (especially the first one when you’re stuck):

Note that escapes are only recognized immediately after newline.

Getting this error when trying to update packages on your linux distro using apt?

This just means that the GPG key is expired and that you need to renew it.

You can list expired keys and get the ID by using this command:

Here, we can see that ID “4BD6EC30” is expired and is leading to the issue.

Let’s now update this key:

And you can now perform the update properly, you won’t get error anymore.

It can be needed to test an UDP connection with a server to ensure that connectivity is working and double check the data received.

Let’s take a simple example with a remote logstash server:
– Server mylogstash.mydomain.local
– Listening on port 5000

On emitter side, we are sending an UDP packet simulating a log line coming from an application:

On receiving server side, we are executing a tcpdump to check that packet is correctly coming with good content:

Here we are! It’s very simple to control UDP flows or simply check connection between 2 servers.