z/OS Communications Server Version 2.Release 4 IP CICS Sockets Guide IBM SC27-3649-40 Note: Before using this information and the product it supports, be sure to read the general information under “Notices” on page 583. This edition applies to Version 2 Release 4 of z/OS® (5650-ZOS), and to subsequent releases and modifications until otherwise indicated in new editions. Last updated: 2021-06-21 © Copyright International Business Machines Corporation 2000, 2020. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents Figures............................................................................................................... xiii Tables.................................................................................................................xxi About this document......................................................................................... xxiii Who should read this document............................................................................................................. xxiii How this document is organized............................................................................................................. xxiii How to use this document.......................................................................................................................xxiv How to contact IBM service............................................................................................................... xxiv Conventions and terminology that are used in this information............................................................ xxiv How to read a syntax diagram..................................................................................................................xxv Prerequisite and related information.................................................................................................... xxviii Summary of changes for IP CICS Sockets Guide............................................... xxxiii Changes made in z/OS Communications Server Version 2 Release 4................................................. xxxiii Changes made in z/OS Communications Server Version 2 Release 3................................................. xxxiii Changes made in z/OS Version 2 Release 2..........................................................................................xxxiii Chapter 1. Introduction to CICS TCP/IP..................................................................1 TCP/IP internets...........................................................................................................................................1 TCP/IP Services Telnet support............................................................................................................. 2 CICS TCP/IP client and server processing............................................................................................. 2 TCP/IP TCP, UDP, and IP protocols........................................................................................................ 2 The socket API communication functions............................................................................................. 3 Programming with sockets.....................................................................................................................3 A typical client-server program flow chart............................................................................................ 6 Concurrent and iterative servers............................................................................................................8 Basic socket calls................................................................................................................................... 9 Server TCP/IP calls...............................................................................................................................10 Client TCP/IP calls................................................................................................................................12 Other socket calls used for servers..................................................................................................... 13 CICS TCP/IP requirements........................................................................................................................ 16 CICS TCP/IP components..........................................................................................................................17 Summary of what CICS TCP/IP provides.................................................................................................. 17 The socket calls....................................................................................................................................17 The IBM listener................................................................................................................................... 18 CICS TCP/IP conversion routines.........................................................................................................18 Rules for configuring the IBM-supplied listener for IPv6................................................................... 19 Monitoring with CICS Explorer.............................................................................................................19 Chapter 2. Setting up and configuring CICS TCP/IP...............................................21 Modifications to the startup of CICS......................................................................................................... 21 Modifying CICS startup (MVS JCL)............................................................................................................ 23 Defining CICS TCP/IP resources................................................................................................................24 Transaction definitions for CICS.......................................................................................................... 24 Using storage protection when running with CICS 3.3.0 or later....................................................... 25 Required program definitions to support CICS TCP/IP....................................................................... 26 Updates to file definitions for CICS TCP/IP......................................................................................... 31 Defining the TCPM transient data queue for CICS TCP/IP.................................................................. 33 iii CICS monitoring................................................................................................................................... 34 CICS program list table........................................................................................................................ 40 System recovery table..........................................................................................................................40 CICS TCP/IP security considerations...................................................................................................42 Modifying data sets for TCP/IP services....................................................................................................42 hlq.PROFILE.TCPIP data set................................................................................................................ 43 hlq.TCPIP.DATA data set.......................................................................................................................43 Adding a z/OS UNIX System Services segment........................................................................................ 44 Configuring the CICS TCP/IP environment................................................................................................44 Building the configuration data set with EZACICD..............................................................................44 Customizing the configuration transaction (EZAC)..............................................................................57 z/OS UNIX System Services environment effects on IP CICS sockets.................................................... 77 Chapter 3. Configuring the CICS Domain Name Server cache................................ 79 CICS DNS cache function components..................................................................................................... 79 VSAM cache file.................................................................................................................................... 80 EZACICR macro.................................................................................................................................... 80 EZACIC25 module................................................................................................................................80 How the DNS cache handles requests...................................................................................................... 80 Using the DNS cache..................................................................................................................................81 Step 1: Create the initialization module.............................................................................................. 81 Step 2: Define the cache file to CICS...................................................................................................84 Step 3: Issue EZACIC25.......................................................................................................................84