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Overview Section 6-3
The two methods of using the socket services are as follows:
• Dedicated Control Bits (Socket Service Request Switches)
Requests can be made to a socket service by setting parameters and
then merely manipulating specific Socket Service Request Switches.
• CMND(490)
Requests can be made to a socket service by sending service request
commands to the Ethernet Unit.
Note One of the main differences between using Socket Service Request Switches
and using CMND(490) is in the number of sockets that can be connected
simultaneously, as shown in the following table.
6-3-2 Using Socket Services with Socket Service Request Switches
Socket services can be used by setting the parameters in a Socket Service
Parameter Area in the CPU Bus Unit Area and then turning ON a Socket
Service Request Switch.
When using Socket Service Request Switches, a maximum of 8 sockets can
be opened simultaneously for the UDP and TCP combined. Also, the same
socket number cannot be used simultaneously for both UDP and TCP. (There
is only one Socket Service Parameter Area for each socket, i.e., the same
area must be used for both UDP and TCP.)
An illustration of using Socket Service Request Switches to execute socket
services is provided below.
Note 1. Socket Service Request Switches in the CPU Bus Unit Area in the CIO
Area are used to send a service request from the CPU Unit to the Ethernet
Unit.
2. The Socket Service Parameters in the CPU Bus Unit Area in the DM Area
are used to specify the service being requested from the Ethernet Unit.
The CPU Bus Unit Area in the DM Area is also used to receive results of
processing from the Ethernet Unit to the CPU Unit.
After setting the required parameters in a Socket Service Parameter Area in
the CPU Bus Unit Area in the DM Area, the Socket Service Request Switches
can be used to request opening, sending, receiving, or closing for either the
UDP or TCP protocol. When requesting a send, send data at the send/receive
data addresses set in the parameter area is sent. When requesting a
Protocol Socket Service Request
Switches
CMND(490)
UDP Total of 8 sockets max. 8 sockets max.
TCP 8 sockets max.
CS/CJ-series PLC
CPU Unit Ethernet Unit
Socket Service
Request Switches
Socket Service
Parameters
Refreshed
(See Note 1.)
Refreshed
(See Note 2.)
TCP data
transfers
UDP data
transfers
Host computer or other device
System
call
User program
Sockets
Sockets