# Long-running clients

<dl class="api-definition">
<dt>Concept</dt>
<dd><a href="/docs/development/opcua/client/long-running-clients">Long-running clients</a></dd>
</dl>

| Type | Description |
|---|---|
| [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) | Provides session based methods to access OPC UA server services. |
| [OpcClientKeepAlive](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientkeepalive/) | Provides keep-alive options used by a client to monitor an established connection and recover from unexpected disconnection. |
| [OpcClientState](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientstate/) | Defines the different states a client may enter. |
| [OpcClientStateChangedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientstatechangedeventargs/) | Provides the event data for the [StateChanged](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/statechanged) event. |
| [OpcDataChangeReceivedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventargs/) | Provides the event data for the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/datachangereceived), [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#datachangereceived) and [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) events. |
| [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | The exception that is thrown when an OPC operation has failed. |
| [OpcNodeIdCollection](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeidcollection/) | Represents a collection of [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) instances. |
| [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) | Provides mechanisms to monitor a set of attributes (= node data) and (node-related) events using notifications being reported from the server to the client. |