Network Services

This chapter provides a brief overview of key points in developing network services, including:

  • Data Channel
  • Control Channel
  • Using the SDK to connect channels in Rust

Before starting this chapter, please make sure you have read and understood the Data Flow section, and are familiar with the generation and consumption timing of queues and related data.

Queues and Data Formats

  • This document defines the data content of the queues between the Broker and network services.

  • Both data and control channels use unicast mode.

    • AMQP properties:
      • durable: true
      • exclusive: false
      • auto-delete: false
      • ttl: determined when generating the network
      • max-length: determined when generating the network
    • MQTT properties:
      • QoS: 1 at the Broker side
      • clean session: true at the Broker side

  • In the Data Flow section, it is mentioned that network services need to retain dataId while processing downlink data for subsequent result reporting.

    • For unreported downlink data, it has no impact on the Broker.
      • Currently retained for one day. If not reported, it will always be marked as "unreported".
    • The application service can decide how to handle downlink data that has not been reported for too long.

  • Rules regarding result:

    • Less than 0 indicates the ongoing process.
      • -2: Indicates that the data is being sent to the network service. Set by the Broker before storing in the database.
      • -1: Indicates that the network service has received it. Must be reported back as -1 via the result queue by the network service.
    • 0 or positive values indicate the completion of processing. At this point, it will be removed from the dldata database, and any further reports cannot be sent back to the application side.
      • All reported by the network service.
      • 0: Successfully sent to the device or the device responded successfully.
      • Positive values: Unable to send to the device or the device responded with an error.

    As the results are currently defined by the network service, the application side still needs to know which network the device is currently bound to. It is recommended to follow the above rules when developing network services to make the presentation on the application side more consistent.

Rust and Using the SDK

For Rust developers, there is an SDK available to assist in developing network services. Usage examples can be found in the Appendix chapter. Here are a few tips on how to use it:

  • Channel maintenance is handled in the mq module's NetworkMgr.
  • One NetworkMgr corresponds to one network service.
  • Only manage NetworkMgr; no need to manually manage the connection status of all queues and AMQP/MQTT properties.
  • Register an EventHandler to receive real-time updates when the queue status changes or data is delivered.
  • You can use send_uldata() and send_dldata_result() to send data to the Broker.