ServerDiscovery QML Type | Qt OPC UA 6.4.1

- Qt 6.4
- Qt OPC UA
- QML Types
- ServerDiscovery
- Qt 6.4.1 Reference Documentation

# ServerDiscovery QML Type

Provides information about available servers. More...

Import Statement: | import QtOpcUa
Since: | QtOpcUa 5.13

- List of all members, including inherited members

## Properties

- connection : Connection
- count : int
- discoveryUrl : string
- status : Status

## Methods

- ApplicationDescription at(index)

## Detailed Description

Allows to fetch and access information about servers known to a server or discovery server.

     QtOpcUa.Connection {
         id: connection
         backend: availableBackends[0]
         defaultConnection: true
     }

     QtOpcUa.ServerDiscovery {
         discoveryUrl: "opc.tcp://127.0.0.1:43344"
         onServersChanged: {
             if (status.isGood) {
                 if (status.status == QtOpcUa.Status.GoodCompletesAsynchronusly)
                     return; // wait until finished
                 if (count > 0) {
                     // choose right server
                     endpointDiscovery.serverUrl = at(0).discoveryUrls[0];
                     console.log("Using server URL:", endpointDiscovery.serverUrl);
                 } else {
                     // no servers retrieved
                 }
             } else {
                 // Fetching servers failed
                 console.log("Error fetching server:", servers.status.status);
             }
         }
     }

     QtOpcUa.EndpointDiscovery {
         id: endpointDiscovery
         onEndpointsChanged: {
             if (status.isGood) {
                 if (status.status == QtOpcUa.Status.GoodCompletesAsynchronusly)
                     return; // wait until finished
                 if (count > 0) {
                     // choose right endpoint
                     console.log("Using endpoint", at(0).endpointUrl, at(0).securityPolicy);
                     connection.connectToEndpoint(at(0));
                 } else {
                     // no endpoints retrieved
                 }
             } else {
                 // Fetching endpoints failed
                 console.log("Error fetching endpoints:", status.status);
             }
         }
     }

## Property Documentation

connection : Connection

The connection to be used for requesting information.

If this property is not set, the default connection will be used, if any.

See also Connection and Connection::defaultConnection.

count : int

Current number of servers in this element. Before using any data from this server discovery, you should check status if retrieval of the information was successful.

See also status and Status.

discoveryUrl : string

URL of the server to retrieve the list of servers from. Every time the URL is changed, a request to the given server is started.

When starting the request, the list of available servers is cleared and the status is set to Status.GoodCompletesAsynchronously. Once the request is finished, status changes. Make sure to check the status before accessing the list of servers.

     onServersChanged: {
             if (status.isGood) {
                 if (status.status == QtOpcUa.Status.GoodCompletesAsynchronusly)
                     return; // wait until finished
                 if (count > 0) {
                     var serverUrl = at(0).serverUrl();
                     console.log(serverUrl);
                 }
             } else {
                 // handle error
             }
     }

See also ApplicationDescription, status, at, count, and Status.

status : Status

The current status of this element. In case the last retrieval of servers was successful, the status should be `Status.Good`.

     if (status.isGood) {
         // Choose endpoint to connect to
     } else {
         // handle error
     }

See also Status.

## Method Documentation

ApplicationDescription at(index)

Returns the application description at given index. In case there are no servers available or the index is invalid, an invalid application description is returned. Before using any returned data, you should check status if retrieval of the information was successful.

     if (servers.status.isGood) {
         if (servers.count > 0)
             var serverUrl = at(0).serverUrl();
             console.log(serverUrl);
             // Choose endpoint to connect to
     } else {
         // handle error
     }

See also count, status, and ApplicationDescription.