In this chapter, we first presented an overview of the framework model, applicable conditions, and application scenarios of local control. We also compared it to remote control, enabling you to assess the suitability of local control functionality based on your unique project requirements. Local discovery plays a pivotal role in local control as it governs the ability of smartphones to search for devices within the LAN. This allows smartphones to retrieve device characteristics and facilitates subsequent control of the identified devices. Therefore, we also delved into the operational mode of the local discovery protocols, specifically in terms of the principle layer. We also conducted a comparative analysis of the characteristics of the two modes: broadcast and multicast, shedding light on their similarities and differences. The most commonly used local discovery protocol is mDNS, which provides you with the flexibility to implement local discovery functionality in your IoT projects. You can also leverage the resource discovery technology inherent in the Bluetooth protocol directly when utilising Bluetooth for control purposes.
Then we introduced the most critical data communication protocols and corresponding data encryption algorithms in local control. The fundamental protocols for data communication in local control are TCP and UDP . While you can directly utilise these protocols for local control, it is generally not recommended due to certain limitations. TCP and UDP are classified as transport layer protocols and do not inherently carry application format data, in contrast to protocols like HTTP and CoAP, which incorporate an application layer on top of the transport layer. Furthermore, it's important to note that transport layer protocols such as TCP and UDP do not support direct encryption of data using protocols like TLS or DTLS. Therefore, relying solely on the transport layer protocol for data transmission may not guarantee the security of the transmitted data. Hence, it is recommended that you utilise protocols such as HTTP with TLS or CoAP with DTLS for data communication in local control scenarios.
Finally, we introduced how to implement the complete local control
function based on the
esp_local_ctrl component in ESP-IDF.
esp_local_ctrl supports local control based on Wi-Fi and Bluetooth,
with data communication protocols that include HTTPS for Wi-Fi and
Bluetooth protocols for Bluetooth. You can get started with local
control development with
esp_local_ctrl component. Additionally, the
esp_local_ctrl component does not support local network device
discovery functionality. You need to implement device discovery
functionality using the mDNS module. The
esp_local_ctrl component is
widely used in ESP-IDF, and you can find provisioning and local
communication features in the
wifi_provisioning component for network
configuration and local communication.
Of course, there are various protocols and implementation methods for
local control. If the
esp_local_ctrl component does not meet your
requirements, you can follow the example codes in sections 8.2, 8.3, and
8.4 to build your own local control framework.