Home Computer Network: A New Way of Networking for DIY Internet of Things

Background: Despite plenty of applications and improvements related to traditional networking schema based on Internet Protocol (IP), there is a lack of a generic networking schema for low-cost Internet of Things, based on non-TCP/UDP protocols, standards and devices. One may also point out limited possibilities for address-free networking at a small scale (within a room, a workplace, at home) based on broadcast and multicast, as well as multi-hop relaying. Method: We took into attention several communication modes and hardware modules for AVR and Raspberry microcontrollers, both wired and wireless, spiked with symmetric cryptography and textual (human-readable) format of the messages. Results: In this paper we propose a new way of networking called Home Computer Network (HCN), devoted to home and DIY applications. HCN protocol stands for a flexible standard of generic, stateless information exchange among two or more nodes, regardless the communication links on the way from a sender node to all the receivers. The proposal covers both address-free and addressable transmission. In the address-free mode, the incoming message is to be accepted by the receiving node based on message contents, i.e., its semantics and parameters. Once a message is accepted, the node performs certain actions related to the message. In parallel, the message is re-transmitted to other communication channels (except the channel the message arrived by) to be inspected by other nodes – this is so called multi-hop communication. To eliminate possible loops in information flow, the repeated messages are identified and eliminated, based on unique descriptors of the messages. In the addressable mode, the message is linked with an identifier of the receiving node – such a message is accepted only by a certain node, and is not propagated in multi-hop mode by any other node. Each message may be encrypted. Due to limited node resources, simple, however powerful encryption standard has been applied, namely xxTEA algorithm, with pre-shared encryption key common for all the nodes. Conclusion: HCN makes it possible to automate the process of linking several micro-controllers at home into a single consistent network, with limited amount of programmers’ work and with very low-cost hardware such as AVR-based computers, Raspberry boards, 2,4GHz and 433/868MHz networking modules, Bluetooth, classical cable connections such as RS-232 and RS-485, 1-wire, SPI, and many other DIY solutions.