IoT and Communication Protocols

The Barracuda App Server (BAS) can act as a network server, a network client, or both. Use this page to select a communication model and find the corresponding BAS API or tutorial. Protocol availability depends on the BAS build and licensed components.

Need	Protocol or interface	BAS component and next step
Request-response APIs for devices, gateways, test tools, or cloud services	HTTP or HTTPS with REST-style resources	Use the BAS server APIs or Lua HTTP(S) client. See the REST tutorials for C and C++ or Lua.
Real-time browser updates, device control, and publish/subscribe messaging	Simple Message Queue (SMQ)	BAS includes the SMQ broker and client interfaces. Start with the SMQ overview, then review SMQ security.
Connect a device to an MQTT broker	MQTT	Use the Lua MQTT client or C/C++ MQTT client. BAS does not replace the external MQTT broker in this model.
Represent industrial edge data through MQTT	MQTT Sparkplug	Use the separate Lua Sparkplug Edge of Network example and library.
Structured industrial data and services	OPC Unified Architecture (OPC UA)	The OPC UA client and server stack is a separate product and is not included in a standard BAS delivery. See the OPC UA API documentation. Precompiled Mako Server packages may include it.
Communicate with industrial controllers and field devices	Modbus TCP	Use the Lua Modbus client.
Bidirectional messages over a persistent connection	WebSockets	Use the Lua WebSocket client and server or the C/C++ WebSocket server. For browser choices, see Browser-to-Server Communication.
Send email notifications	Simple Mail Transfer Protocol (SMTP)	Use the Lua SMTP client.
Obtain and renew TLS certificates	Automatic Certificate Management Environment (ACME)	Use the ACME module. ACME manages certificates; it is not an application-data protocol.

Choose the Communication Model First

HTTP and REST: Use request-response communication when clients need discrete operations, conventional URLs, status codes, and broad tool compatibility.
WebSockets: Use a persistent bidirectional channel when a browser and server exchange frequent, low-latency messages.
SMQ or MQTT: Use publish/subscribe communication when producers and consumers should be decoupled. SMQ integrates browser sessions and targeted messaging with BAS; MQTT connects BAS applications to the wider MQTT ecosystem.
OPC UA or Modbus: Use the industrial protocol required by the equipment, information model, or integration contract.

Whichever protocol you select, define authentication, authorization, TLS, credential provisioning, input limits, and update procedures as part of the system design.