This document describes the purpose and the functions of the Natural Web I/O Interface.
The Natural Web I/O Interface is used to execute Natural applications in a web browser. It fully supports the following:
The display and input of Unicode characters. See Unicode Input/Output Handling in Natural Applications in the Unicode and Code Page Support documentation which is part of the Natural documentation for the different platforms.
Rich internet applications developed with Natural for Ajax.
The Natural Web I/O Interface consists of a server and a client.
The Natural Web I/O Interface server enables you to use a browser as the I/O device for Natural applications. The server does the user authentication, creates the Natural session and handles the I/O between Natural and the client. The Natural Web I/O Interface server is installed on the same machine as the Natural application. For further information on the Natural Web I/O Interface server, see the Natural documentation for the different platforms.
The client handles the communication between the user's web browser and the Natural Web I/O Interface server. It converts the output from the Natural application to web pages, and returns the user input to Natural.
Two types of client are supported:
Natural Web I/O Interface client for displaying character-based applications in the web browser. Maps with GUI controls are not supported in this case. For further information on this type of client, see the Natural documentation for the different platforms.
Natural for Ajax for displaying rich internet applications in the web browser.
The client is installed on a web/application server. This can be done on any machine in the network.
The Natural Web I/O Interface receives data from a Natural application and delivers web pages to the user's web browser. This is illustrated in the following graphic:
The communication steps for executing a Natural application in the web browser are:
The user enters the address (URL) of a logon page in the web browser. The client then displays the logon page in the web browser.
Note:
For information on how to invoke and configure the logon
page, see Client
Configuration.
The user enters all required information for starting a Natural application into the logon page. This information is sent to the client.
The client asks the Natural Web I/O Interface server to start the requested Natural application for this user.
The Natural Web I/O Interface server checks the supplied user ID and password, creates a Natural session for the user and starts the Natural application.
The Natural application returns the first application screen which is then transferred via the Natural Web I/O Interface server to the client and finally as a web page to the web browser.
Different web browsers are supported. Note that cookies and JavaScript must be enabled in the web browser. For a list of the currently supported web browsers, see the browser prerequisites for the type of client that you are using.
The following rules apply:
The Natural Web I/O Interface server can work with any client that has the same or a higher protocol version.
If the server detects that the client is using a version that is lower than the server version, the server replies that the client is too old and the connection is closed.
The client can work with any server that has the same or a lower protocol version.
If the client detects that the server is using a version that is lower than the client version, the client switches to the server version. However, new client functionality is not supported in this case.
The Natural Web I/O Interface server must have the same protocol version as the Natural process that is started by the server. If Natural detects that the server is using a different protocol version, an error message is sent to the user and the connection is closed.
On the different Natural platforms for which the Natural Web I/O Interface is supported, different techiques are used for implementing the server part of the Natural Web I/O Interface. On Natural for Linux, it is implemented as a daemon. On Natural for Windows, it is implemented as a service. On the mainframe, it is implemented as a server. In this documentation, the general term "server" is therefore used for all different kinds of implementation.
There are several restrictions when using the Natural Web I/O Interface with Natural applications on Linux, mainframe or Windows hosts.
Note:
The term "application" refers to application
software. It does not refer to system software or software for
development.
The following restrictions apply:
GUI controls
GUI controls are not supported: dialogs, buttons, radio buttons,
list boxes, list views, check boxes etc. The Natural Web I/O Interface only
supports Natural applications developed without GUI controls.
File transfer
File transfer (for example, with the DOWNLOAD
statement) is not supported by the Natural Web I/O Interface.
Runtime errors
This restriction applies to older Natural versions on Linux and
Windows. As of version 6.3.3, this restriction no longer applies.
Runtime errors in Natural applications are not handled by the
Natural Web I/O Interface. This leads to a loss of the session. Bypass: use the
Natural system variable
*ERROR-TA to handle the
error. Sample Natural error transaction:
DEFINE DATA LOCAL 1 ERR_INFO 2 ERR_NR(N5) 2 ERR_LINE(N4) 2 ERR_STAT(A1) 2 ERR_PNAM(A8) 2 ERR_LEVEL(N2) END-DEFINE INPUT ERR_INFO DISPLAY ERR_INFO TERMINATE END
Terminal commands
Terminal commands are not supported. They do not work when
entered in the Natural for Ajax client.
Natural system variable *INIT-ID
When using the Natural for Ajax client with
Natural applications on Linux, mainframe or Windows hosts, the Natural system
variable *INIT-ID will not be
filled with a value for the terminal type. On Linux and Windows, it will
contain the value "notty". On mainframes, it will
contain a session ID that is unique on that server.
The following restrictions apply to Natural on Linux and Windows hosts (the mainframe does not have these restrictions):
Return to the Natural main screen
You must not use Natural applications that return to the Natural
main screen as this leads to wrong screen display and a loss of the
session.
Natural editors and utilities
You must not use Natural utilities such as SYSMAIN
or SYSDDM and editors such as the program editor as this leads to
wrong screen display and a loss of the session.
Natural system commands
You must not use any Natural system command such as
CATALL, FIND,
GLOBALS, HELP,
KEY, LIST,
RETURN, SCAN,
SETUP or XREF as this
leads to wrong screen display and a loss of the session.