FlowSync

FlowSync implements synchronous request handling for HTTP server nodes and OPC UA server nodes within Connectware. When activated, Connectware suspends response generation until a corresponding MQTT message is received, enabling synchronized processing across different protocols and systems. This enables a closed communication loop between machines and IT systems, confirming every step of the data journey – even when errors occur.

You can customize the behavior of FlowSync through configuration:

• Define custom timeout durations for request-response cycles

• Configure default timeout messages returned to clients

• Specify custom error messages for different error scenarios

FlowSync is part of the Cybus:Node resource.

Processing Flow

The following outlines the data flow from initial request to completion.

1

Initial Request Reception

When a request (HTTP or OPC UA) arrives at the server endpoint:

• The request remains open rather than returning an immediate response

• The system publishes an MQTT message on the /treq topic. The published data has the following structure:

{
  "id": "cb75f252-ebd8-4b33-b39d-b74953c6c99c",
  "timestamp": 1733219059372,
  "value": { ... }
}

• A unique identifier is generated and embedded in the message payload

2

Transaction Completion

Upon receiving the MQTT response message, the system:

• Correlates it with the original request using the unique identifier

• Processes the response data on the /tres topic. The received data has the following structure:

{
  "id": "cb75f252-ebd8-4b33-b39d-b74953c6c99c",
  "timestamp": 1733219059372,
  "value": { ... }
}

• Completes the original protocol-specific request

The transaction remains active until either:

• A valid MQTT response is received

• The configured timeout period expires

Enabling FlowSync

FlowSync functionality is controlled through the node resource configuration in your service commissioning files.

• To implement synchronous processing, set the operation property of a Cybus:Node resource to transaction:

node:
    operation: transaction

FlowSync Example Files

The following sections provide practical examples of service commissioning files that demonstrate how to implement FlowSync with both HTTP and OPC UA connections. Each example includes a complete configuration along with explanations of key aspects to help you understand and adapt FlowSync for your specific needs.

• Example 1 - Node with Transaction Mode (HTTP)
• Example 2 - Node Responds (HTTP)
• Example 3 - Node with Error (HTTP)
• Example 4 - Node with Timeout Error Code and Error Message (HTTP)
• Example 5 - Full Flow (HTTP)
• Example 6 - Full Transactional Data Flow (OPC UA)