Technical data

Table Of Contents
Open Communication via Industrial Ethernet
System Software for S7-300/400 System and Standard Functions - Volume 2/2
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A5E00739858-01
UDP
Unlike with the TCP native and ISO on TCP protocols, with UDP you do not
establish a connection. In this case, when calling the sending block FB 67
"TUSEND" you have to specify the address parameters of the receiver (IP address
and port number). Similarly, after the conclusion of the receiving block FB 68
"TURCV", you will receive a reference to the address parameters of the sender
(IP address and port number).
In order to be able to use the FBs 67 "TUSEND" and 68 "TURCV", you first have to
call the FB 65 "TCON" on both the sending side and the receiving side. This step is
necessary to configure the local communications access point.
With each new call of FB 67 "TUSEND", you re-reference the remote partner by
specifying its IP address and its port number.
During data transmission, information on the length and the end of the message is
also transmitted.
If you have specified the length of the data to be received (LEN parameter of FB 68
"TURCV") to be greater than the length of the data to be sent, FB 68 "TURCV" will
copy the received data completely into the receiver range. After this, it will set NDR
to TRUE and write RCVD_LEN with the length of the sent data.
If you have specified the length of the data to be received (DATA parameter of
FB 68 "TURCV") to be less than the length of the sent data, FB 68 will not copy
any data into the receiver range but instead will supply the following error
information: ERROR = 1, STATUS = W#16#8088.