Chapter
4
4.6.1.
Physical Connections
At sites with more than one machine, the machines are connected to a local area network (LAN)
switch with Ethernet cables. The RVMs can communicate with each other and transfer incoming
and outgoing files.
4.6.2.
File Transfers
An internet connection facilitates the transfer of incoming and outgoing files between the RVMs on
site and the server at Envipco. One of the machines acts as a site control device: it receives files
from Envipco and distributes them to the other RVMs, and it also collects files from the other RVMs
to send to Envipco. This connection may be through a modem on a regular telephone line (a land
line connection), or it may be through a cellular modem. If the site is using a land line modem, the
modem is installed on the PC board in one of the machines. At sites using a cellular modem, the
modem is installed in a lock box outside of the machines.
When a site connects to Envipco, any of the RVMs can act as a site controller. If connected by
cellular modem, data transfers occur even if one or more of the RVMs cannot connect at the time of
data collection and distribution. If the machines are connected by a land line modem, the RVM with
the modem must be running in order for the file transfer to complete.
The software process by which barcode files are transferred by modem from Envipco to the site’s
RVMs is simplified by this summary:
Note:
Each
RVM has a set connection time. This time is different for each
machine, in order to prevent all of the RVMs from trying to connect at
the same time.
1.
When the RVM software starts, it polls the other RVMs to check if any of
them have a newer barcode file.
2.
If it finds a newer barcode file, it receives and installs it.
3.
When an RVM reaches its connection time, it connects to an FTP server
at Envipco and checks for a newer barcode file.
4.
If the FTP server has a new barcode file, the RVM renames it, gets it, and
distributes it to the other RVMs. It then deletes the file from the FTP server.
Whether or not it finds a newer barcode file, it resets its data collection time
for the next day. At that point, it starts again at Step 2.
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