Protocol

Under the brand name IO-Link there is a communication system for the connection of intelligent sensors and actuators to an automation system standardized in IEC 61131-9 under the designation Single-drop digital communication interface for small sensors and actuators (SDCI). The standardization covers both the electrical connection data and a digital communication protocol through which the sensors and actuators exchange data with the automation system. An IO-Link system consists of an IO-Link master and one or more IO-Link devices, i.e. sensors or actuators. The IO-Link master provides the interface to the higher-level controller (PLC) and controls communication with the connected IO-Link devices. ...

The Modbus protocol is a communication protocol based on a master/slave or client/server architecture. It was introduced in 1979 by Gould-Modicon for communication with its programmable logic controllers. In industry, Modbus has become a de facto standard as it is an open protocol. Since 2007, the Modbus TCP version has been part of the IEC 61158 standard. [Wikipedia] As the following diagram shows, Modbus allows communication over different networks: ...

Constrained Application Protocol (CoAP) CoAP is an Internet application protocol specified in RFC 7252. The protocol is used for communication of devices ’nodes’, e.g. embedded devices, that consume very little energy (low-power) and operate in networks with increased data loss (lossy networks), for instance IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs). CoAP can also be used within Internet-based networks for mobile communication via SMS. CoAP is primarily used in the context of the Internet of Things (IoT) and Machine-to-Machine (M2M), as device data/sensor data of small size is usually transmitted. Since this type of data is transmitted at regular intervals (cycles), individual (lost) data packets have no significant impact on the processing systems or applications, such as an IoT platform that processes and/or graphically displays the corresponding sensor data (temperature, rotation speed, etc.). ...

MQTT (Message Queue Telemetry Transport) is an open messaging protocol for machine-to-machine communication (M2M) that enables the transmission of telemetry data in the form of messages between devices, despite high latency or constrained networks. Corresponding devices range from sensors and actuators, mobile phones, embedded systems in vehicles or laptops to fully developed computers. [Wikipedia] The information about the specification listed below comes, among other sources, from the current MQTT specification of IBM. ...

IPv4 Review IPv4 Header Version: 4 IHL (Internet Header Length): length of the header in 32-bit increments. Value 5 = 5 lines x 32 bits TOS (Type of Service): used to prioritize the IP packet (QoS) Total Length: 65535 bytes Identification, Flags & Fragment Offset. Control of fragmentation Flags: Bit 0 is reserved. If bit 1 is set to 0, fragmentation is allowed. If set to 1, not allowed. If bit 2 is set to 0, then it is the last fragment. If 1, more fragments follow. Time to Live: lifetime of the packet. Each router reduces the value by 1 Protocol: e.g. TCP, UDP, ICMP, etc. Header Checksum: checksum. Rarely used. Source / Destination: destination and source address IPv4 & IPv6 Header Differences ...