Instructions For Open User Communication - Siemens SIMATIC ET 200AL System Manual

6.3

Instructions for Open User Communication

Introduction
You set up Open User Communication via the corresponding connection (for example, TCP
connection) as follows:
● By programming in the user programs of the communications partners or
● By configuring the connection in STEP 7 in the hardware and network editor
Regardless of whether you set up the connection by programming or configuring,
instructions are always required in the user programs of both communications partners for
sending and receiving the data.
Setting up the connection via the user program
If the connection is set up by programming, the connection establishment and termination is
implemented using instructions in the user program.
In certain areas of application it is an advantage not to set up the communications
connections statically by configuring in the hardware configuration, but to have them set up
by the user program. You can set up the connections via a specific application program-
controlled and therefore when necessary. Programmed connection setup also allows
connection resources to be released following data transfer.
A data structure is necessary for each communications connection that contains the
parameters for establishing the connection (for example system data type "TCON_IP_v4" for
TCP).
The system data types (SDT) are provided by the system and have a predefined structure
that cannot be changed.
The various protocols have their own data structures (see table below). The parameters are
stored in a data block ("connection description DB") for example of the system data type
TCON_IP_v4.
There are two ways in which you can specify the DB with the data structure:
● Recommendation: Have the data block created automatically in the properties in the
program editor during configuration of the connection for the TSEND_C, TRCV_C and
TCON instructions.
● Create the data block manually, assign parameters to it and write it directly to the
instruction
Necessary for:
– Secure OUC
– Connection over DNS
– E-mail
– FTP
You can modify the connection parameters in the "connection description DB".
Communication
Function Manual, 12/2017, A5E03735815-AF
Open User Communication
6.3 Instructions for Open User Communication
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