**3. M2M communication protocols**

There are several communication protocols responsible for managing the transfer of data between computers on the internet, among them we can mention some examples such as HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol) and SFTP (SSH File Transfer Protocol). When the communication needs to be made between two or more devices (or several applications) connected in a network, the need arises to have a protocol that manages this communication, that is, the exchange of data between the devices in an efficient way considering the characteristics and restrictions imposed by the environment. According to [4], in this scenario, two protocols arise that can be used in restricted environments: Messaging Queue Telemetry Transport (MQTT) and the Constrained Application Protocol (CoAP).

The following will present the MQTT and CoAP protocols, identifying their main characteristics and limitations, in addition to highlighting the best scenarios where each can be applied in the context of Industry 4.0.
