User's Manual

5-1
Chapter 5
Before you begin programming…
The RF Terminal receives messages from the host user program. The Terminal
responds back to the host application program with data that was keyed or scanned
by the Terminal's user. The host application program processes the data and sends
back the next prompt. Each RF Terminal has a unique IP address (or at least a
unique Mac address). The Server program either reports the IP address or for the
sake of compatibility with programs written for 70/700 series terminals, resolves
terminal addresses to a single character Terminal ID (0-9,A-Z, a-z, and -=).
This dialog is established when a Terminal SIGNS ON to the RF network. The
host computer application waits until a Terminal SIGNS ON, then begins its
processing by sending the first prompt out to the Terminal via the Access Point.
Before you begin programming, there are some factors you should take into
consideration during the planning process.
• Plan for system failures. This includes hardware failures,
software failures and operator failures. In order to create an
efficient application, you must put some thought into what you will
do when different parts of the system fail.
• Look for All Errors. Be sure your program is trapping all possible
error conditions that the Server may return to you. The list includes:
Sequence Errors detected
Illegal Command detected
Server Re-Initialized
Addressing a Terminal Not Signed In
Command without an ID
All of these error conditions are detailed in the next chapter. Don’t
forget to program for them; this is a common mistake. Failure to
trap them will give create very strange, unpredictable results.
Even though you don’t think your code will ever make a mistake,
take advantage of feedback that the Server provides. Failure to do
so is a common mistake that eventually results in serious program
failure, sometimes due to hardware problems that go undetected.
• Parse the Returned Strings thoroughly. Don’t assume anything
about the next response from the Server to your program and look
only for the partial string such as the ID only. Parse the string
returned completely, and be sure you are examining every
possibility. Failure to do so is a common mistake.
• Plan for expansion. You may start small (1 Terminal) but try to
create an application that will allow for easy expansion.