Concepts and Structure

XCICS Web support is a collection of XCICS services that enable a XCICS region to act both as an HTTP server, and as an HTTP client.

When XCICS is an HTTP server, a Web client can send an HTTP request to XCICS and receive a response. The response can be a static response created by XCICS from a document template or static file, or an application-generated response created dynamically by a user application program.

1.	System initialization parameters and resource definitions, including TCPIPSERVICE definitions and URIMAP definitions, which are used to configure XCICS Web support and instruct XCICS how to process requests and responses.

2.	XCICS utility programs, which can be used to analyze and process the HTTP requests and responses.

User-written application programs, which are used to receive the HTTP requests and provide material for HTTP responses. These can be Web-aware application programs designed for use with XCICS Web support, or non-Web-aware XCICS application programs that were not originally designed for use with XCICS Web support.

The behavior of XCICS Web support as an HTTP server is conditionally compliant with the HTTP/1.1 specification, as described in RFC 2616 specifications.

When XCICS is an HTTP client, a user application program in XCICS can initiate a request to an HTTP server, and receive a response from it.

The actions of XCICS as an HTTP client are controlled by user-written application programs. The EXEC XCICS WEB application programming interface includes commands that an application program can use to construct and initiate HTTP requests from XCICS, 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.

XCICS Web support also supports non-HTTP requests from clients. You can use many of the components of XCICS Web support, including TCPIPSERVICE definitions, XCICS 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 XCICS Web support use a special protocol (the USER protocol) on the TCPIPSERVICE resource definition, so that they are not subjected to the checks that XCICS carries out for HTTP messages.

In XCICS Transaction Server for z/OS, Version 3 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 XCICS Web support provides for non-HTTP messages is not the same thing as the TCP/IP Sockets interface for XCICS. The IP XCICS Sockets interface supplied with z/OS Communications Server has an application programming interface which allows clients to communicate
directly with XCICS application programs over TCP/IP. XCICS Web support is not involved with this process.