CICS Transaction Gateway V5 The WebSphere ... - IBM Redbooks

1.1.2 Gateway daemon
The Gateway daemon is a long-running process that functions as a server to
network-attached Java client applications (such as applets or remote
applications) by listening on a specified TCP/IP port. The CICS TG supports four
different CICS TG network protocols (TCP, SSL, HTTP, or HTTPS), each of which
requires a different CICS TG protocol handler to be configured to listen for
requests (Figure 1-2).
Java
Client
TCP or SSL
HTTP or HTTPS
Gateway
daemon
Protocol
handler
Distributed platform
CICS TG
CTGJNI.dll
JNI module
Client
daemon
Figure 1-2 CICS Transaction Gateway: distributed platform
APPC
or
TCP62
or
TCP/IP
z/OS or VSE
CICS
Server
The structure of the Gateway daemon is slightly different on z/OS and on
distributed platforms. On distributed platforms (including Linux for S/390), the
CICS TG provides equivalent functions to those provided by the CICS Universal
Client. There are three basic interfaces that are provided to Java client
applications:
External Call Interface (ECI) A call interface to COMMAREA-based
CICS applications
External Presentation Interface (EPI) An API to invoke 3270-based
transactions
External Security Interface (ESI) An API that allows password
expiration management (PEM)
functions to be invoked in CICS, in
order to verify and change user IDs
and passwords
In V5 of the CICS TG, there is now also a new type of protocol handler called
TCPAdmin, which is part of the dynamic trace facility. This allows a Java client to
connect to the CICS TG and dynamically control the CICS TG trace settings. For
further details on how we used this, refer to “Dynamic trace (gateway)” on
page 174.
Chapter 1. CICS Transaction Gateway 7