User's Manual

3-1
Chapter 3
Operational Theory
Before you jump in and start writing a complex host program, it might be nice to
be familiar with the theory behind the operation of your RF Terminal.
Basic RF System communications…
A WIFI system consists of three components – Host Server, Access Points
and RF Terminal. The Access Points are connected to the Server by
Ethernet wiring. The Terminal Device "signs in" by establishing
communication with a Server Program through an Access Point. After the
terminal "signs in" the host program can send a prompt to the terminal with
the ActiveX program interface provided by Worth Data. The application
running on the Server sends a data prompt to the terminal device using the
Ethernet wiring to the Access Point and then by radio link to the terminal
device. The RF Terminal displays the data prompt on the display and waits
for the operator to enter the requested data. Once the operator enters his
data, the RF Terminal transmits the data to the Access Point, which in turn
passes it on to the Server. The application on the host computer processes
the information and sends a new data prompt out to the Access Point and
the whole process begins again.
A little more in depth…
This RF system’s dialogue is Terminal initiated. The Terminal says, “I’m
here, give me something to do.
When you select DEVICE SIGN ON?, the RF Terminal first establishes
communication with the network as follows:
1. It looks for an Access Point with an identical SSID using the Channel
Number in its configuration as the starting channel.
2. Once it finds an access point, it checks to see if the encryption of the
Access Point matches its WEP key.
3. If the unit is configured to obtain its IP address from a DHCP Server, it
requests an IP address from a DHCP Server.
4. If it does not have a fixed Server IP address configured, it does a search
for an application Server.
5. Now the Terminal Device sends a SIGN ON message to the application
Server. All messages include data as well as the transmitter's and
receiver's MAC address, IP address, and Port address.
While attempting to establish communication with the application Server,
the Terminal Device will display the following message:
WAITING ON SERVER TO ACKNOWLEDGE