Micro Focus Enterprise Developer 2.3 for Visual Studio 2015 > Programming > Mainframe Programming > Mainframe Subsystem Support Developer Introduction > About CICS applications > Invoking CICS Programs Externally > IBM CICS Transaction Gateway

IBM CICS Transaction Gateway

Client programs using the CTG APIs can run on the same machine as the Enterprise Server region, or on different physical hardware. In either case, requests are submitted to the target region through the communication layer via the Web Services and J2EE listener.

Programming for IBM CICS Transaction Gateway

You use the CTG APIs (ECI, EPI and ESI) in your client program to communicate with the CICS application running under Enterprise Server. The calls from your client program are passed through the IBM CICS Transaction Gateway to Enterprise Server.

CICS client-side support: The API entry points such as CICSEXTERNALCALL are exposed by modules which are supplied as a dynamic load library on Windows and a callable shared object on UNIX and Linux platforms. Please consult the IBM CICS Transaction Gateway documentation for platform-specific information.
Client programs can add a CALL statement to the dll exposing the required ECI/EPI API, include an INITCALL directive (COBOL), or link the client module to the appropriate .lib file.

Note: To call programs with Java, use the Java API provided by IBM.
Configuration: You need to configure CTG to refer to a named Enterprise Server and a nominated port - this is most commonly done via the IBM CICS Transaction Gateway Configuration Tool. ECI and EPI calls via CTG require the creation of a CTG listener, which can be accomplished via the Listeners tab of the relevant Enterprise Server Administration screen, ensuring that the Endpoint Address corresponds to the specified CTG port, and CICS Transaction Gateway is selected as the supported conversation type.
Restrictions: IBM provides Java classes to create channels and containers in an ECI client, and pass these channels and containers to a CICS application. The mechanism for this feature is provided by the IBM proprietary transport IP interconnectivity (IPIC), which is not supported by Enterprise Server.