L1 Guide – How to Test Connectivity to tt{ClientName}.azure-devices.net on Port 8883 (Linux Only)

1️⃣ Step 1 — Test DNS (Does the domain resolve?)

Run this command:

sudo nslookup tt{ClientName}.azure-devices.net

✔ Expected output if OK:

• It should show an IP address, like:

Name: tt{ClientName}.azure-devices.net
Address: 20.xxx.xxx.xxx

❌ If you see:

• “NXDOMAIN”

• “server can’t find”

• “timed out”

➡ DNS is failing → escalate to L2.

2️⃣ Step 2 — Test Port 8883 Connectivity (MQTT Port)

Use netcat (nc):

sudo nc -zv tt{ClientName}.azure-devices.net 8883

✔ Expected output if OK:

Connection to tt{ClientName}.azure-devices.net 8883 port [tcp/*] succeeded!

This means the machine CAN reach Azure IoT Hub on the MQTT port (8883).

❌ If NOT OK, you may see:

• Connection timed out

• Connection refused

• No route to host

• failed

➡ This means port 8883 is blocked (firewall / network issue).
Escalate to L2/L3.

3️⃣ Final Expected Results (Pass / Fail)

4️⃣ Quick Copy/paste Summary for L1

Tests Run on Linux:

1. DNS Check:
   sudo nslookup tt{ClientName}.azure-devices.net
   Expected: Shows an IP.

2. Port 8883 Check:
   sudo nc -zv tt{ClientName}.azure-devices.net 8883
   Expected: "succeeded!"

If either test fails → Escalate to L2.