We Keep Coding

How can I use MQTT long term in IoT Core?

So first of all, what I really want to achieve: I want to know when an IoT device has stopped working (i.e. lost connection, shut down, basically it's not longer talking to IoT Core). I can't seem to find an implementation for this on GCP.
I have a raspberry pi as my IoT device, I have configured it on IoT core and somewhere I read that since this is not implemented a way to solve it is to create a logging sink which activates a cloud function whenever there is a CONNECT/DISCONNECT log. This would serve my purpose and I have implemented this sink and cloud function to alert me.
I have been following this guide on connecting to MQTT. However, the way the explain it, they set it up such that whenever the expiration time on the JWT is exceeded, they disconnect the client and create a new one to re-new the JWT. This would make it such that I am going to be alerted of connection/disconnection whenever this client needs to be renewed. So I won't be able to differentiate of a real issue from renewals of the MQTT client.
In the same guide, I see that they mention MQTT long term or LTS, and they claim that this way you can set up the client once and communicate continuously through it for the supported time which it says its until 2030. This seems to be what I really want, but I have not been able to connect this way and they don't explain it other than saying the hostname should be mqtt.2030.ltsapis.goog and to use a primary and backup certificates which are different from the complete root CA from the first method.
I tried using basically the same process for setting up the client:
client = mqtt.Client(client_id=client_id)
# With Google Cloud IoT Core, the username field is ignored, and the
# password field is used to transmit a JWT to authorize the device.
client.username_pw_set(
username='unused',
password=create_jwt(project_id, private_key_file, algorithm))
# Enable SSL/TLS support.
client.tls_set(ca_certs=ca_certs, tls_version=ssl.PROTOCOL_TLSv1_2)
but changing the hostname and giving it the primary cert where I would give it the complete ca_certs, but it won't accept it and I am not sure how to do it otherwise with primary and backup certifications. I am looking at the documentation on tls_set, but I don't see where these would go or how they differ from the complete ca certs. I haven't seen any other examples outside of this guide.
I am hoping to be able to connect to this MQTT LTS so that I can maintain the connection without having to constantly renew the client.

The long term MQTT domain lets you use the LTS configuration for a long period of time, not the connection.
As you mention, for your use case the solution would be to activate and use device logs. One of the events is triggered when a device disconnects from IoT Core, and you can use that event to trigger an alert.
Keep in mind that the time limits for the connection are set for security purposes, and the client should renew the connection.

Automatic authentication when connected to Wi-Fi

I'm working on a project where I want any user connected to my Wi-Fi network to be automatically authenticated to an eternal website. So, when the user will try to connect himself to the website, he/she sill see himself automatically logged in.
I had as Idea to build up a mechanism that could authenticate the users of the local network to the external site. The idea is to put in place a server that will be between the inner network and the AP. The server will listen the inner network and when a new user tries logs in, the server gets the Users IP, MAC and other information and then goes to the external site and logs in the user. I tried to use python requests and selenium to automate the connection but nothing still.
That's what I had in mind but I'll like to know which technologies to use and if this type of system already exists.

You can use mac-address of devices to differentiate the users and on server side u can check the ip of a user.

Python client-server - tell if client offline

My basic problem is that I am looking for a way for multiple clients to connect to a server over the internet, and for the server to be able to tell if those clients are online or offline.
My current way of doing this is a python socket server, and python clients, which send the server a small message every 2 seconds. The server checks each client to see if it has received such a message in the last 5 seconds, and if not, the client is marked as offline.
However, I feel that is is probably not the best way of doing this, and even if it is, there might be a library that does this for me. I have looked for such a library but have come up empty handed.
Does anyone know of a better way of doing this, or a library which can automatically check the status of multiple connected clients?
Note: by "offline", I mean that the client could be powered off, network connection disconnected or program quit.

Assuming you are not after ping from server to client. I believe that your approach is fine. Very ofther server will not be able to hit client but it works otherway around. You may run out of resources if you have many connected clients.
Also over this established channel you can send other data/metrics and boom monitoring was born ;-) IF you send other data you will probably reliaze you don't need to send data every 2 secs but only if no other data was sent - boom FIX works this way ( and many other messaging protocol)
What you may like is something like kafka that will transport the messages for you there are other messaging protocols too.. and they scale better then if you just connect all client(assuming you have many of them)
Happy messaging

Good Morning i am working a same project and i want to post my approach.
When a client is connected to my server with client, address = sock.accept() we can take his ip with ip_client = address[0]. Assuming you have a list with the connected ips you can append the ip with connected_clients.append(ip_client)
finally you have a list with the connected ips
make a Thread or inside an infinitive loop write the following code
for connected in connected_clients:
response = os.system("ping -c 1 " + connected)
if response == True:
continue
else:
connected_clients.remove(connected)
don't forget to the input os command on the beginning and you have made a beckon of connected clients

python graypy simply not sending

import logging
import graypy
my_logger = logging.getLogger('test_logger')
my_logger.setLevel(logging.DEBUG)
handler = graypy.GELFHandler('my_graylog_server', 12201)
my_logger.addHandler(handler)
my_adapter = logging.LoggerAdapter(logging.getLogger('test_logger'),
{ 'username': 'John' })
my_adapter.debug('Hello Graylog2 from John.')
is not working
I think the issue is the url that should send to /gelf
because when I curl from the terminal to my graylog server , it works
curl -XPOST http://my_graylog_server:12201/gelf -p0 -d '{"short_message":"Hello there", "host":"example1111.org", "facility":"test", "_foo":"bar"}'

Open your Graylog Webapp, click 'System'. You will see a list of links on the right. On of them is 'Input', click this one.
Now you have an overview of all running inputs, listening on different ports. On top of the page you can create a new one. There should be a drop box containing certain modes for the input listener (I think 'GELF AMQP' is standard). Change this one to GELF UDP and click 'Launch new input' in the next dialogue you can specify a port for the service.
You also have to set a node where the messages have to be stored. This node as (or should have) the same IP as your whole graylog2 system.
Now you should be able to receive messages

I think you've setup your input stream For Gelf TCP instead of UDP. I set up a TCP Stream and it got the curl message. However my python application wouldn't send to the stream. I then created a Gelf UDP stream and voila! I ran into this same issue configuring my Graylog EC2 Appliance just a few moments ago.
Also make sure firewall/security groups aren't blocking UDP protocol on port 12201 as well.
Good luck, and I hope this is your issue!

How to give a python client a port number from a python server

I'm trying to build a simple python server that a client can connect to without the client having to know the exact portnumber. Is that even possible? The thought is to choose a random portnumber and using it for clients to connect.
I know you could use bind(host, 0) to get a random port number and socket.getsockname()[1] within the server to get my portnumber. But how could my client get the portnumber?
I have tried socket.getnameinfo() but I don't think I understand how that method really works.

In order to do that the server must listen on a certain port(s).
This means the client(s) will need to interact on these ports with it.
So... no it is impossible to do that on some random unknown port.

You need to advertise the port number somehow. Although DNS doesn't do that (well, you could probably cook up some resource record on the server object, but that's not really done) there are many network services that do. LDAP like active directory (you need write rights), DNS-SD dns service discovery, universal plug and play, service location protocol, all come to mind. You could even record the port number on some web page somewhere and have the client read it.

Take a look at Zeroconf, it seems to be the path to where you are trying to get to.