Chapter 9. Exploring Network Protocols
Network protocols are an important piece of a connected system. Network protocols define rules about how devices at different locations should communicate.
Using a weather station as an example, we will discuss different roles that devices can play in a network. The Hypertext Transfer Protocol (HTTP) is based on requests and responses.1 When a weather display requests information from a server, the embedded device acts as client. When an embedded device provides weather data, it can act as server. Sometimes, a device can be both client and server.
While HTTP is stateless, other network protocols support maintaining “connections” between devices. For example, with the transmission control protocol (TCP) or websockets, transmissions of data packets can happen without prior requests. The WebSocket protocol is particularly popular for pushing data to a web browser—for example, whenever new data is available.
In the Node.js ecosystem, there are libraries to work with all kinds of network protocols. Support for HTTP and TCP comes in the form of Node.js core modules. For the WebSocket protocol, you can fetch open source libraries via npm.
Another important network protocol is the MQTT protocol, which is used to send messages across networks. MQTT will be discussed in Chapter 11 in the context of cloud services for connected devices.
The Hypertext Transfer Protocol
HTTP describes the transfer of state between client and server. HTTP is one of the ...
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