Ewon Cosy Proxy and Siemens S7-1500CPU

Hi guys,

I am trying to connect to a Siemens S7-1512C CPU that is seated on the LAN side of the Ewon Cosy 131.

The structure is as follows:

Machine LAN:

  • Ewon LAN IP:
  • PLC IP:
  • PC IP:

Company Network:

  • My Laptop IP:
  • Ewon WAN IP:

Ususally I would use NAT1:1 in order to make the PLC public to the company network but the customer doesn’t want this because they say that then all the ports to the PLC are open.
That is the reason why I am now trying to use the built in proxy feature (port forwarding) in order to reach the PLC over the Ewon WAN interface from the company network.
For now I am “simulating” the connection in our company before the machine is shipped to the customer, so there is no specific task or data that I want to transmit. Just “go online” to see that it is possible at all.

I have configured the Com config as follows:

  • ProxyEnabled = 1
  • Proxy Proto1 = 2
  • ProxySide1 = 1
  • ProxyPort1 = 102
  • ProxySrvPort = 102
  • ProxySrcIpAddr1 =
  • ProxyExtItf = 0
  • NatItf = 2
  • WANItfProt = 2
  • FwrdToWAN = 1

In the PLC I have set the “router” to (LAN IP of Ewon).

I then use “Extended go online …” and type in the IP address of the target device: (WAN IP of Ewon).

The “Profinet Explorer” seems to detect the PLC:

In Ecatcher I retrieved the Gateways and can see the proxy on port 102, the firewall is set to “standard”:

In the event logs of the Ewon I can see a few error messages:

What is this tsap and how could its length be invalid?

Any ideas? Do I need to configure the Siemens CommunicationSettings in a specific way?

The Realtek adapter is where I am connected to our company network (IP via DHCP) and WiFi is disabled.

Do I need to add a route on my laptop?

BTW: over the VPN I still can connect to the PLC on its IP

Here are the Support files:
Backup (11).etar.gz (23.6 KB)

Thanks and Regards


We are migrating to a new platform. Please go to support.hms-networks.com and either create a support case or a forum topic there for help with this issue.

In regard to the errors here, they appear to be related to the PROFINET communication, but we’ll have to take a closer look after you create a support case.

Thank you!

Hi Kyle,


I opened a new support case.



Great - thank you! It looks like it’s been assigned to our Central Europe office so they will be in touch with you soon.