Open User Communication
6.4 Open User Communication with addressing via domain names
Communication
74 Function Manual, 12/2017, A5E03735815-AF
Setting up a TCP connection via the domain name of the communication partner
For TCP communication via the domain name you need to create a data block with the
TCON_QDN system data type yourself, assign parameters and call it directly at the
instruction. The TCON, TSEND_C and TRCV_C instructions support the system data type
TCON_QDN:
To set up a TCP connection via the domain name of the communication partner, follow these
steps:
1. Create a global data block in the project tree.
2. Define a tag of the data type TCON_QDN in the global data block.
The example below shows the global data block "Data_block_1" in which the tag
"DNS Connection1" of data type TCON_QDN is defined.
Figure 6-2 Data type TCON_QDN
3. Program the parameters of the TCP connection (for example the fully qualified domain
name (FQDN)) in the tag of data type TCON_QDN.
4. Create a TCON instruction in the program editor.
5. Interconnect the CONNECT parameter of the TCON instruction with the tag of the data
type TCON_QDN.
In the example below, the CONNECT parameter of the TCON instruction is
interconnected with the tag "DNS connection1" (data type TCON_QDN).
Figure 6-3 TCON instruction
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