> For the complete documentation index, see [llms.txt](https://docs.cybus.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cybus.io/1-11-0/documentation/services/flowsync/flowsync-example-6.md).
# Example 6 - Full Transactional Data Flow (OPC UA)
This example demonstrates a flow starting with an OPC UA method call, performing an HTTP request and giving back the HTTP request result as method call result via OPC UA.
The configuration connects dns.google on the north side with a custom OPC UA method on the south side. The OPC UA server provides a method `getIpForDomain` that accepts a domain name (e.g., cybus.io) as input and returns the corresponding IP address as output.
You can access the OPC UA server via `opc.tcp://127.0.0.1:4841/UA/CybusOpcuaServer`.
* If the domain is successfully resolved, the method returns the IP address.
* If no DNS record is found, it returns a BadNotFound error.
For more information on the FlowSync configuration properties, see [Cybus:Node](/1-11-0/documentation/services/service-commissioning-files/resources/cybus-node.md#operation).
{% file src="/files/7YkET7WzmDDLCl0cWSTH" %}
{% code title="flowsync-example-6-full-transactional-data-flow-opc-ua.yaml" lineNumbers="true" %}
```yaml
description: FlowSync - Example 6
metadata:
name: example 6
version: 1.0.0
resources:
# ------------------------------------------------
# Our Endpoints for dns.google (north side)
# ------------------------------------------------
googleDnsConnection:
type: Cybus::Connection
properties:
protocol: Http
connection:
scheme: https
host: dns.google
dnsEndpoint:
type: Cybus::Endpoint
properties:
topic: dns
protocol: Http
connection: !ref googleDnsConnection
publishError: true
read:
path: /resolve
# ---------------------------------------
# Our OPCUA Server and Nodes (south side)
# ---------------------------------------
opcuaServer:
type: Cybus::Server::Opcua
properties:
hostname: 127.0.0.1
allowAnonymous: true
securityPolicies: ['None']
securityModes: ['None']
rootNode:
type: Cybus::Node::Opcua
properties:
browseName: Cybus
nodeId: ns=1;s=Cybus
parent: !ref opcuaServer
nodeType: Object
getIpForDomainNode:
type: Cybus::Node::Opcua
properties:
topic: getIpForDomain
browseName: getIpForDomain
nodeId: ns=1;s=getIpForDomain
parent: !ref rootNode
nodeType: Method # mark node as method
operation: transaction
inputArguments:
- name: domain
dataType: String
description: the domain to resolve
outputArguments:
- name: ip
dataType: String
description: the IP address of the domain
# ------------------------------------------------
# The mappings forwarding requests and responses
# ------------------------------------------------
Mapping:
type: Cybus::Mapping
properties:
mappings:
- subscribe:
endpoint: !ref getIpForDomainNode
publish:
endpoint: !ref dnsEndpoint
rules:
- transform:
expression: >-
(
{
"id": $.id,
"query": {
"name": $.value.inputArguments[0].value
}
}
)
- subscribe:
endpoint: !ref dnsEndpoint
publish:
endpoint: !ref getIpForDomainNode
rules:
- transform:
expression: >-
(
{
"id": $.id,
"timestamp": $.timestamp,
"value" : $.value.Status = 0 ? {
"outputArguments": [
{
"value": $.value.Answer[0].data
}
]
} : undefined,
"error" : $.value.Status != 0 ? {
"code": "BadNotFound",
"message": "Domain not found"
} : undefined
}
)
```
{% endcode %}
---
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