IoT protocol stack overview in IOT Protocols - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the correct layer for MQTT in the IoT protocol stack

In the IoT protocol stack, where does the MQTT protocol primarily operate?

A Network layer

B Application layer

C Data link layer

D Physical layer

💡 Hint

Think about which layer handles communication protocols that applications use to exchange data.

MQTT is an application layer protocol designed for lightweight messaging between devices.

💻 Command Output

intermediate

Output of a command showing active IoT network interfaces

What is the expected output of the command ifconfig on a Linux IoT device that has a Wi-Fi interface named wlan0 active?

IOT Protocols

ifconfig

A

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet 192.168.1.10  netmask 255.255.255.0  broadcast 192.168.1.255

B

eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 10.0.0.5  netmask 255.0.0.0  broadcast 10.255.255.255

C No interfaces found

D

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
inet 127.0.0.1  netmask 255.0.0.0

💡 Hint

Look for the interface named wlan0 with an IP address in the output.

The wlan0 interface is the Wi-Fi interface and shows its IP address and status when active.

❓ Configuration

advanced

Correct configuration snippet for CoAP server endpoint

Which configuration snippet correctly sets up a CoAP server endpoint on port 5683?

A

coap_server:
  port: 443
  protocol: udp
  resource: /sensor/data

B

coap_server:
  port: 80
  protocol: tcp
  resource: /sensor/data

C

coap_server:
  port: 5683
  protocol: tcp
  resource: /sensor/data

D

coap_server:
  port: 5683
  protocol: udp
  resource: /sensor/data

💡 Hint

CoAP typically uses UDP on port 5683.

CoAP is a UDP-based protocol and uses port 5683 by default for server endpoints.

❓ Troubleshoot

advanced

Troubleshoot why an IoT device cannot connect using MQTT

An IoT device fails to connect to the MQTT broker. Which of the following is the most likely cause?

A The device is connected to the wrong Wi-Fi SSID

B The device is sending HTTP requests instead of MQTT messages

C The device is using TCP port 1883 but the broker expects port 8883 with TLS

D The device is using UDP port 1883 instead of TCP

💡 Hint

Check the port and protocol expected by the MQTT broker.

MQTT typically uses TCP port 1883 for unencrypted and 8883 for encrypted TLS connections. Using the wrong port or protocol causes connection failure.

🔀 Workflow

expert

Order the steps to securely onboard an IoT device using TLS

Put the following steps in the correct order to securely onboard an IoT device using TLS certificates.

A 1,2,3,4

B 1,3,2,4

C 2,1,3,4

D 3,1,2,4

💡 Hint

Think about the logical order of generating keys, getting certificates, installing them, then connecting.

The device first creates a key and CSR, then the CSR is signed by a CA, the signed certificate is installed, and finally a secure connection is established.