Softing

 Following is the syntax used by Softing for OPC Data Access and OPC Alarms&Events servers, respectively:

opcda://computerName/progId/{clsid}
opcae://computerName/progId/{clsid}

When both ProgID and a version-independent ProgID are available from the server browsing, Softing places just the normal ProgID (version-dependent) to the URL. Note that this is a difference from OPC NET API (described further below). The computerName can be an empty string (for a local computer). Also, the progId may be empty altogether, and the client will simply use the CLSID.

Kepware

 Kepware documents following syntax for the URL parameter of their Connect method:

opcSpecification://hostName/serverIdentifier

For OPC Data Access servers, the serverIdentifier has the form below, where the {clsid} is optional:

progID/{clsid}

Originally, Kepware has allowed only "opcda" for the opcSpecification, but as you can see further below, they have later generalized it to support OPC XML-DA and OPC Unified Architecture as well.

Notes from Kepware documentation

For OPC DA servers, the API will attempt to connect using the ClassID first. If the ClassID is not given (or is found to be invalid), the API will attempt to connect using the ProgID.

OPC DA Example

opcda://opcua.demo-this.com/Kepware.KEPServerEX.V5
opcda://127.0.0.1/Kepware.KEPServerEX.V5/{B3AF0BF6-4C0C-4804-A122-6F3B160F4397}

OPC XML-DA Example

http://127.0.0.1/Kepware/xmldaservice.asp

OPC UA Example

opc.tcp://127.0.0.1:49320