Distributed 5250 Emulation Model

The Virtual Terminal Client/Server Model example shows a model for a distributed systems environment between a work station and an iSeries. The client program resides on the work station, while the server program resides on the iSeries^(TM). This model is similar to the way the iSeries supports an iSeries Access work station function.

Virtual Terminal Client/Server Model Example

The client program running on the work station shown in the example does the following:

• Accepts data from the server program and displays the data on the work station display
• Accepts data from the work station keyboard
• Converts the data from the format required by the work station display and keyboard to the format required by the server program (5250 data stream)
• Sends the data to the server program on the iSeries

The link between the client program and server program uses DOS and i5/OS^(TM) communications support. This may be LU 6.2, TCP/IP, or some other communications protocol.

You can write a server application program in any iSeries-supported high-level language (HLL), such as the ILE C programming language. The server program provides work station support for the system acting as the server. The virtual terminal APIs allow a server program to read and write virtual terminal data. Virtual terminal data is always in a 5250 data stream format. See the IBM 5494 Functions Reference book, SC30-3533, for more information on 5250 data streams. This book can be viewed online through the IBM Publications Center.

The virtual terminal APIs provide an interface between the server program and the virtual terminal supported by the i5/OS licensed program. The virtual terminal represents the i5/OS link between the server program and the iSeries application and is managed entirely by the i5/OS licensed program.

The iSeries application is a licensed program or a user-written application that performs a standard data transfer to a work station. This application can be written in any iSeries-supported HLL.