QueryServers is used to find Server applications that meet the specified filters.
Any Client is able to call this Method, however, the set of results returned may be restricted based on the Client’s user credentials.
The applications returned shall pass all of the filters provided (i.e. the filters are combined in an AND operation). The serverCapabilities parameter is an array and an application will pass this filter if it supports all of the specified capabilities.
Each time the GDS creates or updates an application record it shall assign a monotonically increasing identifier to the record. This allows Clients to request records in batches by specifying the identifier for the last record received in the last call to QueryServers. To support this the GDS shall return records in order starting from the lowest record identifier. The GDS shall also return the last time the counter was reset. If a Client detects that this time is more recent than the last time the Client called the Method it shall call the Method again with a startingRecordId of 0.
The lastCounterResetTime parameter is used to indicate that the counters on records had to be reset for some reason such as a Server restart. The Client may not use any recordId received prior to this time to set the value for the startingRecordId in a new call.
The return parameter is a list of ServerOnNetwork Structures. The mapping from a ApplicationRecordDataType to an ServerOnNetwork is shown in Table 15.
Table 15 – ApplicationRecordDataType to ServerOnNetwork Mapping
|
ApplicationRecordDataType |
ServerOnNetwork |
Notes |
|
applicationId |
-- |
Ignored |
|
applicationUri |
-- |
Ignored |
|
applicationType |
-- |
Ignored |
|
applicationNames |
serverName |
The name that best matches the preferredLocales for the current Session is returned. If there is no Session the first element is returned. |
|
productUri |
-- |
Ignored |
|
discoveryUrls |
discoveryUrl |
A ServerOnNetwork record is returned for each discoveryUrl in the ApplicationRecord. |
|
serverCapabilities |
serverCapabilities |
|
|
-- |
recordId |
This is the recordId assigned by the QueryServers call. It may be used as the startedRecordId in a subsequent call to QueryServers. |
Signature
QueryServers(
[in] UInt32 startingRecordId
[in] UInt32 maxRecordsToReturn
[in] String applicationName
[in] String applicationUri
[in] String productUri
[in] String[] serverCapabilities
[out] UtcTime lastCounterResetTime
[out] ServerOnNetwork[] servers
);
|
Argument |
Description |
|
INPUTS |
|
|
startingRecordId |
Only records with an identifier greater than this number will be returned. Specify 0 to start with the first record in the database. |
|
maxRecordsToReturn |
The maximum number of records to return in the response. 0 indicates that there is no limit. |
|
applicationName |
The ApplicationName of the Applications to return. Supports the syntax used by the LIKE FilterOperator described in OPC 10000-4. Not used if an empty string is specified. The filter is only applied to the default ApplicationName. |
|
applicationUri |
The ApplicationUri of the Servers to return. Supports the syntax used by the LIKE FilterOperator described in OPC 10000-4. Not used if an empty string is specified. |
|
productUri |
The ProductUri of the Servers to return. Supports the syntax used by the LIKE FilterOperator described in OPC 10000-4. Not used if an empty string is specified. |
|
serverCapabilities |
The applications returned shall support all of the server capabilities specified. If no server capabilities are provided this filter is not used. |
|
OUTPUTS |
|
|
lastCounterResetTime |
The last time the counters were reset. |
|
servers |
A list of Servers which meet the criteria. The ServerOnNetwork structure is defined in OPC 10000-4. |
Method Result Codes (defined in Call Service)
|
Result Code |
Description |
|
Bad_UserAccessDenied |
The current user does not have the rights required. |
Table 16 specifies the AddressSpace representation for the QueryServers Method.
Table 16 – QueryServers Method AddressSpace Definition
|
Attribute |
Value |
||||
|
BrowseName |
2:QueryServers |
||||
|
References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
|
0:HasProperty |
Variable |
0:InputArguments |
0:Argument[] |
0:PropertyType |
Mandatory |
|
0:HasProperty |
Variable |
0:OutputArguments |
0:Argument[] |
0:PropertyType |
Mandatory |