158
Se
ct
io
n 7
Mo
dbus
Commun
ic
a
tion
s
Prot
ocol
RFID System
User's Manual
(Modbus TCP)
Section 7
Host Communications Specifications
Modbus Communications Protocol
Communications between the host device and the Reader/Writer are performed on a client-server
basis. The computer, PLC, or other host device is the client and the Reader/Writer is the server.
Although you can change the setting of the IP address of the Reader Writer as required, port number
502 is always used for Modbus TCP communications.
Only one host can be connected to the Reader/Writer. If the Reader/Writer accept the request of connection from host-B while
host-A is connected to the Reader/Writer, the connection between the Reader/Writer and host-A will automatically disconnect
and the new connection with host-B will be established.
Client
(host de
v
ice)
Ser
v
er
(Reader/
W
riter)
Connection re
qu
ested.
Connection re
qu
est ackno
w
ledged.
Q
u
ery sent.
Response sent.
Q
u
ery sent.
Response sent.
Disconnection re
qu
ested.
Disconnection re
qu
est ackno
w
ledged.
Processing
exec
u
ted.
Processing
exec
u
ted.
