To call an existing COBOL server
Use the IDL Extractor for COBOL to extract the Software AG IDL and, depending on the complexity of the extraction, also an SVM file.
Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:
use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation
generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester
See Server Examples for z/OS IMS MPP for COBOL RPC Server examples.