Communication failures

This section describes the behavior of the Gateway Communication Driver in case of failed communications with the data source, client, or a remote OPC server.

Failed Communication with Data Source

Gateway Communication Driver behaves in the following manner in the case of failed communication with a data source:

• The Gateway Communication Driver attempts to periodically reestablish a connection with the data source up to the maximum number of retry attempts as specified in its Reconnect Attempts parameter.

  Note: The Gateway Communication Driver is not responsible for starting the data source server, unless the source protocol supports it. OPC has this capability.

• The Gateway Communication Driver marks all items being read from the data source with Bad quality. OPC carries a sub-status of Comm Failure.

• Write attempts to the data source are rejected with an appropriate error code.

  The behavior of the Gateway Communication Driver during the communications failures with an ArchestrA data source is described below:

  Communication Failure	OPC Data Quality
  Break between PLC and DIObject	0x1B
  DIObject node disconnected	0x00
  Node with ArchestrA UserDefined ApplicationObject disconnected	0x04
  ApplicationObject undeployed	0x00
  WinPlatform undeployed on Gateway node	0x00
  Gateway Communication Driver node disconnected (communicating with local OPC client)	0x04

Failed Communication with Client

Gateway Communication Driver behaves in the following manner in the case of failed communication with a client:

• The Gateway Communication Driver un-subscribes (deactivates) all items on the data source that were previously subscribed to by the failed client. (Exceptions: Those items required by other, still connected, clients remain subscribed. Also, in the case of an OPC client, Gateway Communication Driver maintains subscriptions to all items on the data source previously subscribed to by the failed client.)

• The Gateway Communication Driver accepts future attempts to reconnect from the client. Reconnection is the responsibility of the client.

Failed Communication with a remote OPC Server

The Gateway Communication Driver behaves in the following manner in case of failed communication with a remote OPC Server:

• The OPC Client application fails to create an OPC Group

• The OPC Client application does not display data updates. Consequently, data values remain unchanged or display ‘Bad Quality’

• The logger reports a COM error 0x80040202

This cause of this issue can be either an Invalid Username/Password, or Guest-only access. For the troubleshooting steps of the above issues, refer to the Communication Failure: OPC Callback and Issues section in the Communication Drivers Pack Help.