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CTI 2572 Installation and Operation Guide
33
Bit 16 controls the priority given to this client application. When bit 16 is set to 0
(offset 4 = 0x0000), the client application will execute with a normal priority. When
bit 16 is set to 1 (offset 4 = 0x0001), the client application will execute with a high
priority. High priority client applications will be scheduled before all server
applications and all client applications operating at normal priority. One use of the
high priority setting could be sending critical alarm data. You should use normal
priority unless your application definitely requires high priority.
NOTE:
Use the high priority setting with care. You can significantly degrade the 2572 network server
performance by setting several client applications to high priority then continuously triggering data
transfer commands for the client applications.
Offset 5 Type of Service - Selects between UDP (connectionless) or TCP (connection-
oriented) service. Using UDP, the local socket is created but no connection is
established with the target node. Using TCP, a virtual circuit connection is
established with the other node. If the TCP connection cannot be established, the
2572 will indicate an error.
NOTE:
If TCP is selected and the connection with the target node (remote host) is lost, the 2572 will report
a socket connection error code (such as 240A - Socket not Connected) the next time you attempt to
read/write data. The connection may be lost due to problem with the remote host or the network.
After the error is acknowledged, the 2572 will complete error recovery by automatically closing the
socket. A subsequent attempt to read/write data will result in a 00A6 (connection not active) error.
See Appendix B for error code listings. Your logic should re-execute the Create Socket command if
the connection is not active.
Offset 6-7 IP Address - If the IP ADDRESS SELECTION option bit in Offset 4 is set to 0, these
words specify the IP address of the destination node. Since the IP address consists of
32 bits, the address is contained in two 16 bit words. An IP address of 0.0.0.0 (0000
0000 hex) or greater than 223.255.255.255 (DFFF FFFF hex) will return an error
Offset 8 Unused - This word is not used when creating a TCP/IP socket. It should be set to 0.
Offset 9 TCP/UDP port number - If the IP A
DDRESS SELECTION option bit in Offset 4 is set
to 0, this word specifies the TCP/UDP port number of the remote node. If you are
accessing another 2572, you will typically set this value to 1505 (the recommended
value for the 2572 PLC server). If you are using UDP and bit 15 of offset 4 is set to
1, then this address becomes the default port number.
Offset 10-15 Unused - These words are unused and should be set to 0.