Siemens CM 1542-1 Operating Instructions Manual page 35

A separate connection must be established for each communications partner even if
identical blocks of data are being sent.
After a successful transfer of the data, a connection can be terminated. A connection is also
terminated by calling "TDISCON".
Note
Connection abort
If an existing connection is aborted by the communications partner or due to disturbances on
the network, the connection must also be terminated by calling TDISCON. Make sure that
you take this into account in your programming.
Connection descriptions in system data types (SDTs)
For the connection description, the blocks listed above use the parameter CONNECT (or
MAIL_ADDR_PARAM with TMAIL_C). The connection description is stored in a data block
whose structure is specified by the system data type (SDT).
Creating an SDT for the data blocks
You create the SDT required for every connection description as a data block. You generate
the SDT type in STEP 7 by entering the name (e.g. "TCON_IP_V4") in the "Data type" box
manually in the declaration table of block instead of selecting an entry from the "Data type"
drop-down list. The corresponding SDT is then created with its parameters.
The following SDTs can be used.
● Configured connections:
– TCON_Configured
● Programmed connections:
– TCON_IP_V4
– TCON_QDN
– TCON_IP_RFC
– TMail_V4
– TMail_FQDN
You will find the description of the SDTs with their parameters in the STEP 7 information
system under the relevant name of the SDT.
CM 1542-1
Operating Instructions, 07/2019, C79000-G8976-C355-04
For transferring frames via TCP
For transferring frames via TCP or UDP
For transferring frames via TCP or UDP
For transferring frames via ISO-on-TCP
For transferring e-mails addressing the e-mail server using an IPv4 address
For transferring e-mails addressing the e-mail server using the host name
Configuration, programming
4.6 Program blocks for OUC
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