5-1
Chapter 5
Before you begin programming…
The “Application Host Program” or “Server Program” is a program designed and
written by the user that incorporates the WD802Term ActiveX control. When an
802 RF Terminal is turned on and “Signs In” to the host, the WD802Term control
reports a terminal ID number to the host application that is unique to that terminal.
The IP address of a particular terminal can also be obtained.
Once an 802 RF Terminal is signed in, it 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 802 RF Terminal has a unique IP
address (or at least a unique Mac address). The host program can obtain any
terminal’s IP address or, for the sake of compatibility with programs written for
70/700 series terminals, resolve terminal addresses to a single character Terminal ID
(0-9,A-Z, a-z, and -=) by using the WD802Term ActiveX component.
The dialog between 802 RF Terminal and Application Host is established when a
terminal connects to the 802.11 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 an 802.11/b 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.
