CICS® web support is a collection of CICS services that enable a CICS region to act both as an HTTP server, and as an HTTP client.
When CICS is an HTTP server, a web client can send an HTTP request to CICS and receive a response. The response can be a static response created by CICS from a document template or static file, or an application-generated response created dynamically by a user application program.
The behavior of CICS web support as an HTTP server is conditionally compliant with the HTTP/1.1 specification, as described in RFC 2616. See The HTTP protocol for more information about the HTTP specifications.
When CICS is an HTTP client, a user application program in CICS can initiate a request to an HTTP server, and receive a response from it.
The actions of CICS as an HTTP client are controlled by user-written application programs. The EXEC CICS WEB application programming interface includes commands that an application program can use to construct and initiate HTTP requests from CICS, and to receive responses sent by servers. URIMAP resource definitions can be used to provide information such as a URL or a client certificate label.
CICS web support also supports non-HTTP requests from clients. You can use many of the components of CICS web support, including TCPIPSERVICE definitions, CICS utility programs, and user-written application programs, to provide request handling for any request format that you have defined. Non-HTTP messages that are handled by CICS web support use a special protocol (the USER protocol) on the TCPIPSERVICE resource definition, so that they are not subjected to the checks that CICS carries out for HTTP messages.
In CICS Transaction Server for z/OS®, Version 5 Release 1, this facility is primarily intended to provide support for requests from user-written clients that use nonstandard request formats. The processing that takes place for requests is defined by the user. The facility does not provide specific support for any formally defined protocols which are used for client-server communication.
The support that CICS web support provides for non-HTTP messages is not the same thing as the TCP/IP Sockets interface for CICS. The IP CICS Sockets interface supplied with z/OS Communications Server has an application programming interface which allows clients to communicate directly with CICS application programs over TCP/IP. CICS web support is not involved with this process. z/OS Communications Server IP Sockets Application Programming Interface Guide and Reference describes the CICS Sockets interface.