Exchange/SNA Manual

Step-by-Step Instructions
Using the Exchange/SNA Programmatic Interface
4–10 104700 Tandem Computers Incorporated
Step-by-Step
Instructions
Most uses of the Exchange/SNA programmatic interface follow the same general
sequence of steps. This sequence is outlined below.
1. Start the line server.
2. Open a subdevice supported by the line server.
3. Set the operational parameters (does not apply to console operations).
4. Perform the operation.
5. Close the subdevice.
Each step is explained in detail below.
Step 1: Start the Line
Server
Before your program can use the programmatic interface, the line server must be
started. The only way to start the line server is to use the CONNECT command. For
instructions on how to use the CONNECT command to start a new line server, see
Section 2. If all you want to do is start a line server, you can exit the command
interpreter immediately after the CONNECT command.
You do not need to start a line new server each time you want to run a program that
uses the programmatic interface. Your programs can use any existing line server and
can use the same line server again and again as long as that line server exists. Of
course, the line server must be connected to the host system with which your program
wants to communicate and must meet the requirements of your application. For
example, if your program requires that data be sent to the host as transparent data, the
line server must have been set up to send transparent data for it to meet the
requirements of your program.
Step 2: Open a Subdevice
Supported by the Line
Server
After the line server has been started, your program must open a subdevice supported
by the line server to communicate with the host system.
To open a subdevice, call the OPEN procedure. For a complete description of the
OPEN procedure, see the Guardian Procedure Calls Reference Manual. For a description
of how to use the OPEN procedure with Exchange/SNA, see Section 5.
In the call to the OPEN procedure, your program specifies whether wait or nowait I/O
operations will be performed with the subdevice. If you specify nowait I/O
operations, you are limited to one outstanding I/O operation at a time.