How to set the converter mode and what it is used for can be read from the article How to set the I/O module with PLC in converter mode.
If we exclude other things, such as multiple network cards on the PC or enabled PC firewalls, we will also check the firewall settings on the PLC! In the file /etc/iptables.rules we find something like this:
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [4962:573959]
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m tcp –dport 12345 -j ACCEPT
-A INPUT -m state –state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -m icmp –icmp-type 8 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 22 -j ACCEPT
-A INPUT -p udp -m udp –dport 8002 -j ACCEPT
-A INPUT -j DROP
COMMIT
The line with the UDP port number 8002 is important for the function of the converter, through which the communication takes place in the converter mode. If this line is missing in the file, we will add it there, save the file and restart the PLC.
