ProtoLink developed a DDE to OPC gateway to allow one or more OPC clients to have access to data provided by one or more DDE servers.
To accomplish this, the gateway simultaneously serves as a DDE client and an OPC server. The DDE client portion of the gateway is designed to handle two versions of DDE, namely DDEML from Microsoft and AdvanceDDE from Rockwell Software. The gateway supports a variety of distributed network topologies.
Special measures were necessary to support the OPC specified browsing of the gateway’s namespace, which is comprised of namespaces exposed by DDE servers which inherently do not support such browsing. Specifically, a set of “namespace definition” files must be created for any DDE server that is to be browsed. This set of files will include a single “conversation definition” file and one or more “item namespace” files. The gateway supports browsing of the address space of all DDE servers that have had namespace definition files created for them.
The gateway also implements several statistical counters which may be monitored using the standard Performance Monitoring application that ships with Windows.