**4.4 Communication standards**

The IoT supports some communication standards that can be defined as:


As can be seen in **Figure 8**, the pattern Telemetry becomes suitable for the MQTT protocol, because it has a public/subscribed model, which is equivalent to the telemetry standard. CoAP is not suitable for the Telemetry standard because the connection needs from the system (client) to the server, which faces addressing problems such as mobile roaming or NAT [9]. The CoAP protocol has a better performance for the query communication pattern in relation to the MQTT protocol, since it is based on the request/response model (**Figure 9**). The MQTT has a

certain difficulty of implementation in the *Consultation* pattern because it has the need to define a response topic for the communication since there is no way for it to

addressing problems detailed in textit Telemetry and MQTT does not support

native result paths, thus requiring a results topic (**Figure 11**).

*Communication pattern example command for (a) MQTT, (b) CoAP.*

*Communication pattern example query for (a) MQTT, (b) CoAP.*

*Interaction Protocols for Multi-Robot Systems in Industry 4.0*

*DOI: http://dx.doi.org/10.5772/intechopen.97481*

exchange protocol has the following advantages over CoAP:

For the *Command* pattern, both protocols face difficulties. CoAP faces the same

Finally, in the *Notification* pattern, the CoAP addressing problems, also listed in the Command and Telemetry patterns, are present. On the other hand, the model MQTT publishes/subscribes to the notification architecture, presenting problems only if better flow control is needed for a large amount of data at high rates [4].

Based on the information listed in the previous sections, it can be concluded that both protocols (MQTT and CoAP) are considered for use in restricted environments and on devices with battery, processor and limited memory. However, although the two protocols were designed for application in limited environments, the MQTT

• The transport with small overhead makes MQTT an interesting solution for networks with resource constraints, low bandwidth and high latency;

• The MQTT is more geared for communication "many to many" (using the

TCP/IP protocol (**Table 3**)), since the COAP is more geared for

be readily constructed (**Figure 10**).

**Figure 10.**

**Figure 11.**

**165**

**5. Conclusion and related works**

#### **Figure 8.**

*Telemetry communication pattern example for (a) MQTT, (b) CoAP.*

**Figure 9.** *Example of communication pattern notification for (a) MQTT, (b) CoAP.*
