How do you configure OPC Expert to communicate through a hardware firewall in a strict network security environment?
Configuring OPC Expert Through a Strict Hardware Firewall
The firewall requirements for OPC Expert depend on which OPC protocols and connection modes are in use. OPC DA using DCOM requires the broadest firewall exceptions and is the most challenging to manage in strict environments. OPC UA uses a single configurable TCP port and is straightforward to accommodate. OPC Expert’s Tunneler reduces any connection to a single port regardless of the underlying OPC protocol, which is the most firewall-friendly configuration available.
Firewall Requirements for OPC DA (DCOM)
OPC Classic DA relies on DCOM, which requires TCP port 135 for the DCOM endpoint mapper and a configurable range of dynamic ports for the actual data communication. In strict firewall environments, administrators typically need to configure DCOM to use a fixed port range and then open that range on the firewall. OPC Expert’s Troubleshooting module identifies when DCOM is being blocked and provides verbose guidance on which ports are involved and what registry-level DCOM configuration steps are needed. OPC Expert itself detected a firewall-blocked condition during the webinar demonstration and immediately advised the operator to address the firewall on the remote computer.
Firewall Requirements for OPC UA
OPC UA connections use a single TCP port, with 4840 as the default, though this is configurable on the OPC UA server. To allow OPC UA communication through a hardware firewall, you open that single port for TCP traffic between the client and server machines. Because OPC UA does not use DCOM, there are no dynamic port ranges to manage. OPC Expert tests OPC UA connections individually against different security modes, allowing you to confirm connectivity before and after firewall changes.
Using the Tunneler for Firewall-Friendly OPC DA
For OPC DA connections that must cross a firewall and where configuring a DCOM port range is impractical or not permitted, the Tunneler reduces the requirement to a single TCP or OPC UA port. The Tunneler runs on the server-side machine, listens on the configured port, and handles all DCOM communication locally. The firewall only needs to permit traffic on that one port. If the network uses HTTPS as the transport, the Tunneler can use port 443, which is almost universally permitted in even the most restrictive environments.
Relevant Tools
OPC Expert (OPC Tunneler): Reduces all OPC DA firewall requirements to a single configurable port, making it the recommended approach for strict network environments where DCOM port ranges cannot be opened.
OPC Expert (Troubleshooting OPC and DCOM): Identifies when firewall rules are blocking OPC communication, describes the specific ports or DCOM settings involved, and provides step-by-step remediation guidance.
Understanding which protocol is in use is the starting point for any firewall configuration. For new integrations in strict environments, designing around OPC UA or the Tunneler from the beginning avoids the DCOM port management challenge entirely.