Connection timeout
If there is no reply to a request for a connection from a communication partner within the time set here, OPC jobs are cancelled with an error message. Values from 2,000 to 100,000 ms can be set.
Since successful establishment of a connection can take some time depending on the network structure, the connection establishment timeout should be longer than the job timeout.
The connection timeout starts with the start of the request for the connection. This time depends on the configuration of the connection characteristics (see above). Two cases are possible:
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Keeping the connection established permanently: In this case, the connection establishment request begins with the start of the OPC server for the S7 protocol. This start is triggered by connecting an OPC client to the OPC server and searching the S7 namespace and/or by adding and actively monitoring an S7 item.
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Connection when required: The request for connection establishment starts with the first access to tags of this S7 connection.
If the S7 connection is interrupted in running operation, an attempt is made to reestablish the connection. This resets and restarts the connection timeout.
Job timeout
Network jobs directed to the partner device are monitored by the job timeout. If no response is issued to a network job within the job timeout, the corresponding OPC jobs are cancelled with an error message. Values from 1 to 100,000 ms can be set.
The job timeout starts at the time a network job is sent in the OPC server. In general, there is only an indirect relationship between write/read/monitor jobs at the OPC interface. Several OPC items can be handled for each network job. Additionally, several OPC clients can request the same OPC item for each network job.
Furthermore, the "Optimize write access" and "Optimize read access" parameters play a role because several OPC jobs can be assembled there on the network level.