Natural Web I/O Interface Server Concept and Structure

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# Natural Web I/O Interface Server Concept and Structure

This document describes the concept and the structure of the server for the Natural Web I/O Interface which is designed for use on z/OS.

The following topics are covered:

- Web I/O Interface Server Concept

- Front-End Stub NATRNWO

- Front-End

- Server Monitor

## Web I/O Interface Server Concept

A Natural Web I/O Interface server is a multi-user, multi-tasking application. It can host Natural sessions for multiple users and execute their applications concurrently.

The concept is based on the "serverized" Natural runtime system. Its architecture comprises a server front-end stub (Web I/O Interface server stub `NATRNWO`) that uses the Natural front-end to dispatch Natural sessions and to execute applications within these sessions.

The Natural Web I/O Interface server architecture basically consists of:

- Front-end stub

  The stub `NATRNWO` is launched to initialize a Natural Web I/O Interface server. It listens for incoming connection requests an launches a Natural session for executing the application.

- Front-end

  The front-end is called (together with the Natural runtime system) by the front-end stub for session initialization/termination, application execution and session roll-in/roll-out.

- Server monitor

  A monitor task allows the administrator to control the server activities, to cancel particular user sessions or to terminate the entire server, etc.

## Front-End Stub NATRNWO

The multi-user, multi-tasking, front-end stub `NATRNWO` is launched to initialize a Natural Web I/O Interface server.

The following topics are covered below:

- Stub Description

- Natural System Variables Used

### Stub Description

The task executing the server initialization (`TMain`) basically is the main listener which waits for incoming requests from the Web I/O Interface client. It owns a session directory to manage multiple clients (users) and their corresponding remote Natural sessions. `TMain` has the task to accept all incoming requests and to dispatch them to other subtasks (`TWork`). The process is as follows:

- First, a server connection issued by the user on the client side (the Login button of the Web I/O Interface client) connects to `TMain` to establish a connection.

- Next, `TMain` inserts the client into its session directory, attaches a new `TWork` subtask and passes the connection to TWork.

- `TWork` initializes a new Natural session and starts the specified Natural application program.

- While the application performs I/O requests, `TWork` intercepts the I/O data and passes them to the Web I/O Interface client for processing the I/O. The I/O reply is sent back to the server and the server continues the application.

- If the application terminates (reaches the `NEXT` mode), TWork terminates the Natural session and drops the connection to the Web I/O Interface client.

That is, each client owns one subtask `TWork` on the Natural Web I/O Interface server. This subtask runs a Natural session (and within the Natural session, a Natural application) and remains active as long as the application is running.

### Natural System Variables Used

Within a Natural Web I/O Interface server session, the following Natural system variables are used:

- `*TPSYS` contains `SERVSTUB`,

- `*DEVICE` contains `BROWSER`,

- `*SERVER-TYPE` contains `WEBIO`.

## Front-End

Under z/OS, the Natural front-end required for a Natural Web I/O Interface server is a Natural batch front-end driver, which should be LE enabled. See sample installation jobs for details.

Under z/OS, the front-end is called (together with the Natural runtime system) by the front-end stub for session initialization/termination, request execution and session roll-in/roll-out.

The Natural front-end required for executing the Natural sessions under control of CICS is the Natural remote front-end `NATCSRFE` that is delivered with the Natural Web I/O Interface server. For more information, refer to the Natural Web I/O Interface Server CICS Adapter documentation.

## Server Monitor

To enable the administrator to monitor the status of the Natural Web I/O Interface server, a monitor task is provided which is initialized automatically at server startup. Using the monitor commands, the administrator can control the server activities, cancel particular user sessions, terminate the entire server, etc. See Operating the Web I/O Interface Server.

### On this page

- Web I/O Interface Server Concept
- Front-End Stub NATRNWO
- Front-End
- Server Monitor