Shannon information entropy attempts to predict the smallest possible average size of lossless encoding of data. This is useful when writing compression software as it provides a target estimate to which we can attempt to compress a file without losing any of the information contained inside it when it is subsequently decompressed.
Cast V2 is the protocol used in communications with Chromecast dongles and Google Home’s. It is not an open protocol, but as it is built into things like Chrome it is possible to reverse engineer how it works. Creating a library makes it easy to control these devices with PHP.
mDNS is a zero configuration protocol. Essentially it runs a localised, distributed, DNS service. It is used primarily by consumer devices, such as iPads, to enable the provision of services without burdening the consumer with technical configuration requirements.