Read Sharp UP-3301 (serv.man5) Service Manual online
Broadband and the POS – June 2003 – Paul Burton 10
Detail
So we have now set up the system we can describe how it works using the IP addresses
shown in the diagram.
Under normal conditions when the POS is connected on a LAN the PC asks the POS for Data
and the POS sends it or the PC can ask the POS can it send preset data, the POS
acknowledges this and the PC sends it.
We must also consider that every IP address has many “sockets” sockets are individual
connections within 1 IP address. The best way to visualize this is to consider a cable with
many strands of wire in. Each strand represents one socket. This means on one IP address
many different communications can be made at one time.
From the above diagram we are looking at a single IP address, on it we can communicate
World Wide Web pages along with POS and FTP. All at the same time, and without
interference.
Firstly lets look at the PC asking for sales data.
1. The PC software as it would do on a LAN sends the enquiry to the POS the address of the
POS is set in this software. In the example the address is set to 81.24.193.102. So the PC
asks address 81.24.193.102 on socket 49152 for the sales data.
2. The enquiry passes to IP address 81.24.193.102, which in this case is the router. The
router is not a POS and therefore does not understand the request. However the “Port
Redirection” states that if ANY data is received on any IP address on port 49152 send it
IP address 192.168.0.1. This is does
3. Address 192.168.0.1 receives the data. We can see that IP address 192.168.0.1 is the
POS and the data is received and processed.
Socket 21 (FTP)
Internet FTP
Socket 80
(WWW)
Socket 49152
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