CTI 2572-B - Chapter 9. Camp Client Commands; Overview; CAMP IP Multicast Operation

CTI 2572-B / 2500C-2572-B Installation and Operation Manual 37
CHAPTER 9. CAMP CLIENT COMMANDS
9.1. Overview
The CAMP client commands are used when you wish to use PLC logic to initiate communications with another
IP host, such a CTI communications module or a CTI 2500 Series controller. You can also use this capability to o
send unsolicited data to your HMI application. For example, you might use this function to report alarms to a
supervisory PC, avoiding the requirement to continuously poll for alarm data.
The CAMP Client commands use the PLC Command Interface described in CHAPTER 7. PLC COMMAND
INTERFACE OVERVIEW.
9.2. CAMP IP Multicast Operation
Most client applications use IP unicast, where a CAMP request is sent to a single IP host, to communicate with
another network device. However, applications that write the same set of data to multiple IP hosts can benefit
by using IP multicast. Rather than sending multiple write requests to each IP host, you can use IP multicast to
write the data to all of the participating IP hosts using a single write command. This reduces network loading
and simplifies the client logic.
The TCP/IP protocol reserves a block of IP addresses) for multicast use. CTI 2572-A, 2572-B, and CTI 2500P-
ECC1 modules can be configured to accept packets with a multicast address. See APPENDIX C. IP ADDRESS
INFORMATION for guidelines on selecting multicast addresses
Only modules whose CAMP servers are configured to accept the same multicast address as the client will
process the request. CAMP servers not configured with a multicast address or configured with a different
multicast address will ignore the message. This allows you to create a group of modules that will participate in
a specific multicast session.
You can configure a 2572-B module to receive on a multicast address using the same methods used to
establish the other TCP/IP network parameters.
1. If you are using the PLC Start method, the multicast address can be specified in the Start Network
Services command block. See Section Start Network Services Command Block.
2. If you are starting the module using IP parameters stored in FLASH, you can use the Web Server
interface to enter the multicast address.
Caution:
To prevent inadvertent overwriting of V memory data in other PLCs, ensure that only the
modules that you want to participate in the multicast session are configured with the
multicast address.