Implementing transfers in the application layer.
A critical element of IoT is transporting packets of valuable data from devices to the application environment. Network connections are base-level requirements, with different protocols for implementing data transfers in the application layer.
We have the hard-won experience to help you determine the right protocols to suit your needs. Here are a few of many the protocols we use:
Hypertext Transfer Protocol (HTTP) and its secure version (HTTPS) function in a "client-server" mode, typically used where a web browser client interfaces with a web server. APIs between systems often use HTTP, as well. HTTP is an option for devices with sufficient computing power and bandwidth, access to an IP network, and not expected to run for years on a battery or with energy harvesting.
Message Queuing Telemetry Transport (MQTT) is ideal for message transport in environments requiring small code footprints and effective bandwidth management. Like most protocols build on top of TCP, it can be secured using TLS encryption. MQTT fits well in an open architecture where all data needs to be exchanged between large numbers of publishers and subscribers. It has become one of the most common protocols for IoT.
Constrained Application Protocol (CoAP) is an application layer protocol intended for resource-constrained Internet devices such as wireless sensor nodes. Built on top of UDP, it has very low overhead, and can be secured using DTLS encryption.
Transmission Control Protocol (TCP) is a transport layer protocol for connecting remote computers, transporting and ensuring the delivery of messages over supporting networks and the Internet. TCP provides reliable data delivery between applications running on computers communicating via an Internet Protocol (IP) network.
User Datagram Protocol (UDP) is a connectionless protocol that uses datagrams to allow devices to exchange messages. UDP avoids the overhead of error checking and session management, when these are not needed or are handled by the application, making it a good choice for non-critical data sent from IP-based power-constrained devices. UDP is sometimes also used in lower layers of other protocols, like CoAP.
Modbus has actually been around since the late 1970's, and has become a de facto standard for communications between sensors and actuators in industrial environments. The Modbus physical layer can be a simple RS-485 serial connection or Ethernet using TCP. Its simplicity and wide support from hundreds of suppliers will probably ensure its survival for another 50 years or more.