What Is OPC Factory Server?
OPC Factory Server (OFS) is Schneider Electric’s OPC DA (Data Access) server — the middleware software that connects Modicon PLCs to SCADA systems, HMIs, historians, and other OPC-enabled client applications. It acts as the data bridge between the proprietary Schneider/Modicon communication world and the open OPC standard that SCADA software uses to read and write PLC data.
Without OFS (or a similar OPC server), a SCADA system cannot directly access symbolic variable names from a Unity Pro / EcoStruxure Control Expert PLC project. OFS provides this critical connection, translating SCADA tag requests into Modicon-native protocol communications and returning real-time process data.
Version 3.63 SP3 is the latest release, adding security vulnerability fixes, Windows 11 and Windows Server 2022 compatibility, and several enhancements to the configuration tool and server behavior.
OFS is developed by Schneider Electric and is primarily distributed through AVEVA (formerly Wonderware) as a prerequisite component with SCADA products like AVEVA System Platform, InTouch, and Geo SCADA Expert. It can also be licensed independently for use with third-party SCADA platforms.
What Is OPC DA and Why Does It Matter?
To understand OFS, you need to understand OPC DA (OPC Data Access) — the classic OPC standard developed in 1996 by the OPC Foundation.
OPC DA is a Windows COM/DCOM-based client-server protocol for real-time data exchange between industrial control systems and supervisory software. It defines a standard interface where:
- OPC Servers connect to field devices (PLCs, DCS, RTUs) and expose their data as named items (tags)
- OPC Clients (SCADA, HMI, historian software) subscribe to these items and receive real-time updates
OPC DA was the dominant industrial data exchange standard from the late 1990s through the 2010s and remains widely deployed in operational facilities. OFS 3.63 implements OPC DA 1.0, 2.0, and 3.0.
Important context for 2024–2026: OPC DA is a mature, stable technology but is gradually being replaced by OPC UA (Unified Architecture), which is platform-independent, encrypted by default, and designed for modern IT/OT convergence. Schneider Electric now offers EcoStruxure OPC UA Server Expert as the successor to OFS. For new projects, OPC UA Server Expert is the recommended path. For existing OFS installations, continued use is fully supported but migration should be planned.
Supported Modicon PLC Families
OFS supports communication with all major Modicon PLC families:
Current Generation:
- Modicon M340 — medium-range PLC, Ethernet communication via BMX NOE modules (Modbus TCP, UMAS protocol)
- Modicon M580 — high-end PLC with native Ethernet backplane
- Modicon M262 — motion and machine controller
Classic/Legacy Generation:
- Modicon Quantum — large modular PLC, Ethernet via NOE modules
- Modicon Premium / TSX Premium — mid-range modular PLC
- Modicon Momentum — distributed I/O controller
- TSX Micro — compact PLC series
- TSX Nano — entry-level compact PLC
- TSX Series 7 — older modular series
- TSX/PCX Compact — small compact PLCs
For PLC families programmed with Unity Pro / EcoStruxure Control Expert, OFS provides native symbolic access — variable names from the PLC program can be imported directly into OFS without manual address mapping to Modbus registers. This is one of OFS’s most significant productivity advantages over generic Modbus OPC servers.
OFS Architecture
How OFS Fits into a Modicon SCADA System
SCADA / HMI / Historian
|
OPC DA Client interface
|
OPC Factory Server (OFS)
|
Communication Driver Layer
(UMAS / Modbus TCP / Modbus Plus)
|
Network (Ethernet / Modbus Plus)
|
Modicon PLC(s)
OFS runs as a Windows service on a PC connected to both the Modicon PLC network and the SCADA network. Multiple OPC client applications can connect to a single OFS instance simultaneously, all receiving data from the same underlying PLC connections.
Server Editions
OFS is available in three functional editions:
OFS Large — full-featured production edition with no item count restriction. Supports OPC XML protocol and web interface. This is the standard enterprise edition.
OFS Small — reduced edition with a 1,000-item limit. OPC XML protocol and web interface are not available. Suitable for small installations or test environments.
OFS Demo — same features as OFS Large but limited to 3-day runtime per execution session. Used for evaluation and testing only.
OFS WSP (WorkStation Package) — bundled installation package including all three editions above.
What’s New in OFS 3.63 SP3
SP3 is the latest service pack for the 3.63 version branch, released in 2024. Key changes:
Security Vulnerability Fixes
- CVE-2021-26414 mitigation — Windows DCOM Server Security Feature Bypass protection adapted for KB5004442 deployment (note: both OFS server and OPC-DA client must be updated)
- CWE-611 fix — Configuration tool XML External Entity (XXE) injection vulnerability resolved
- Configuration tool protected against reverse-engineering and code injection
- Server protected against out-of-bounds task allocation
- .NET Framework requirement updated to v4.8 — due to end of support for .NET ≤ 4.6.1; setup will fail if .NET 4.8 is not installed
- Configurable batch file executed at server shutdown removed (security hardening)
- Modbus SL and XIP communication drivers upgraded to v14.16.0.0
- Zlib library updated to v1.3
Bug Fixes
/Q devicesModbus maximum register count corrected (was erroneously limited to 59 instead of 125)- Server closure hang fixed when occurring during data dictionary reload
- System timestamping crash fixed on bursts of events with large numbers of event sources
Enhancements
- Windows 11 and Windows Server 2022 compatibility confirmed
- Server status window now shows working set memory (current physical memory in use) and commit size (virtual memory reserved) — valuable for monitoring large deployments
- New alias reconnection policy: configurable reconnection retry count and disconnection timeout per device
- OPC DA AddItems operation improved — no longer blocked during data dictionary reload (items update on the fly, except DDTs and String Arrays accessed globally)
- Memory footprint reduced and fragmentation improved
- New license model for driver mode
- Silent install mode support
Installation Guide
Prerequisites
Before installing OFS 3.63 SP3, ensure:
- Operating System: Windows 10, Windows 11, Windows Server 2016, 2019, or 2022 (64-bit)
- Microsoft .NET Framework 4.8 installed (check via Control Panel → Programs → Turn Windows features on or off, or run
dotnet --list-runtimes) - Microsoft Visual C++ 2015-2022 Redistributable (x86 and x64) installed — OFS SP3 updates the link to the current version
- Administrator privileges on the installation machine
- No earlier version of OFS currently installed (must uninstall first if upgrading from a version earlier than SP2; SP2 to SP3 in-place upgrade is supported)
Installation Steps
- Download the OFS 3.63 SP3 package from Schneider Electric’s website or your authorized distributor
- Run the installer as Administrator
- Accept the license agreement
- Select the edition to install (Large, Small, Demo, or WSP for all)
- Configure the installation directory (default:
C:\Program Files (x86)\Schneider Electric\OFS) - Complete the installation — OFS registers as a Windows service that starts automatically
Post-Installation: DCOM Configuration
OFS uses Windows DCOM for OPC DA client connections. After installation, DCOM permissions must be configured to allow OPC client applications to connect:
- Run
dcomcnfgfrom the Windows Run dialog - Navigate to Component Services → Computers → My Computer
- Right-click “My Computer” → Properties → COM Security tab
- Configure Launch and Activation Permissions and Access Permissions to allow the accounts used by OPC clients
For remote OPC clients (client on a different PC from OFS), additional Windows Firewall rules and DCOM machine-level configuration are required.
Configuration: Connecting to Modicon PLCs
Step 1 — Open the OFS Configuration Tool
Launch OFS Configuration Tool from the Start menu. This graphical interface manages all device definitions, alias groups, and item configurations.
Step 2 — Create a Device Definition
In the OFS Configuration Tool:
- Right-click on Devices → New Device
- Select the device type matching your PLC model:
- Unity (M340, M580, Quantum via Unity Pro) — for Unity Pro / EcoStruxure Control Expert projects
- Modbus Ethernet — for Modbus TCP/IP direct register access
- Modbus Plus — for legacy SA-85 card connections
- TSX Fipway — for FIP bus connections
- Other protocol options for legacy Modicon families
- Configure the device parameters:
- IP Address — PLC’s Ethernet module IP (e.g., 192.168.1.100)
- Port — typically 502 for Modbus TCP
- Device ID / Slave number — for Modbus (M340 typically uses 255 for Modbus TCP)
- Polling rate — how frequently OFS requests data from the PLC
Step 3 — Import Variables (Unity Pro / EcoStruxure)
For PLCs programmed with Unity Pro / EcoStruxure Control Expert, OFS can directly import the variable list from the PLC project rather than requiring manual tag address entry:
- In Unity Pro / EcoStruxure Control Expert, export variables to an
.XVMfile:- Open the Variables & FB Instances editor
- Filter for the variables you want to expose (typically
%MW*address variables) - Select variables → right-click → Export → XVM format
- In OFS Configuration Tool, associate the
.XVMfile with the device definition - OFS now has symbolic access to all exported variables — SCADA clients can address items by their Unity Pro variable name (e.g.,
S1:M340_PLC.Valve1_Open) rather than by Modbus register addresses
This symbolic access is a major productivity advantage — SCADA tag databases use the same meaningful names as the PLC program, dramatically reducing configuration errors.
Step 4 — Configure Alias Groups (Optional)
Alias groups allow you to organize OFS items into logical groups for browsing by OPC clients. This makes it easier for SCADA engineers to locate tags when building the HMI.
Step 5 — Save and Start the Server
Save the configuration and start the OFS Windows service. The server connects to the configured PLCs and begins serving data to OPC clients.
OFS Limits and Capacity
| Parameter | OFS Large | OFS Small |
|---|---|---|
| Maximum OPC items | Unlimited | 1,000 |
| Maximum OPC connections | 300 | 300 |
| Maximum OPC groups per connection | 1,000 | 1,000 |
| OPC XML protocol | ✅ | ❌ |
| Web interface | ✅ | ❌ |
| OPC DA versions | 1.0, 2.0, 3.0 | 1.0, 2.0, 3.0 |
The 300 connection and 1,000 group limits were introduced in SP3 as a security hardening measure to prevent out-of-bounds resource allocation.
Integrating OFS with Common SCADA Platforms
AVEVA System Platform / InTouch
OFS is distributed as a prerequisite with AVEVA System Platform and InTouch. When AVEVA software is installed, OFS is included and its license is typically managed through AVEVA’s licensing system. The integration is native — AVEVA software recognizes OFS items automatically.
Geo SCADA Expert (formerly ClearSCADA)
OFS is a required prerequisite for Geo SCADA Expert when using Schneider PLCs. Install OFS before installing Geo SCADA Expert; Geo SCADA cannot install OFS on a machine that already has OFS installed.
Citect SCADA (now AVEVA Plant SCADA)
Citect has built-in drivers for Modicon PLCs that can work without OFS for direct Modbus connections. However, OFS is commonly used with Citect for symbolic variable access and centralized PLC data management — especially in larger systems where Citect’s tag database is fed through OFS rather than directly polling PLCs.
Ignition SCADA
Inductive Automation Ignition can connect to OFS as an OPC DA client using Ignition’s built-in OPC-COM/DA module. Alternatively, for Modicon M340 with firmware supporting OPC UA (BMX NOE 0110 with firmware v2.0+), Ignition can connect natively via OPC UA without requiring OFS.
Third-Party SCADA (WinCC, iFIX, Wonderware Historian)
Any OPC DA compliant application can connect to OFS. The DCOM configuration is the most common integration challenge — ensure firewall rules and DCOM permissions are correctly configured for remote connections.
Troubleshooting Common Issues
OPC Client Cannot Connect to OFS
Symptom: SCADA reports OPC server unavailable or connection refused.
Causes and fixes:
- Verify OFS Windows service is running (Services → OPC Factory Server)
- Check Windows Firewall is not blocking DCOM ports (TCP 135 and dynamically assigned ports)
- Verify DCOM permissions allow the client application’s user account to launch/access OFS
- For remote client connections, ensure
dcomcnfgmachine-level permissions include the client computer’s account
Tags Show BAD Quality in SCADA
Symptom: OPC items appear in SCADA but show BAD or UNCERTAIN quality.
Causes and fixes:
- Verify PLC is online and responding — check OFS Status window for device connection status
- Confirm PLC IP address and port in OFS device configuration are correct
- For M340: verify the BMX NOE module IP matches the OFS device configuration
- For Quantum: check PLC CPU quality status via
#PLCQualStatussystem item in OFS - After EcoStruxure Control Expert build changes, some items may temporarily show BAD quality during data dictionary reload — this is normal and self-resolves
DCOM Security Errors After Windows Update
Symptom: OPC connections fail after Windows security updates, especially KB5004442.
Fix: OFS 3.63 SP2 and SP3 include specific handling for CVE-2021-26414 / KB5004442. Both the OFS server and all OPC-DA client applications must be updated to versions that handle this security change. If only one side is updated, connections will fail.
.NET Framework Installation Failure (SP3)
Symptom: SP3 installer fails with a .NET Framework error.
Fix: Install Microsoft .NET Framework 4.8 before running the SP3 installer. Download from Microsoft’s official website.
OFS vs. EcoStruxure OPC UA Server Expert — Migration Planning
Schneider Electric has confirmed that OFS is a mature product and OPC UA Server Expert is the strategic replacement. Key differences:
| Aspect | OFS 3.63 | EcoStruxure OPC UA Server Expert |
|---|---|---|
| Protocol | OPC DA (COM/DCOM) | OPC UA |
| Security | DCOM-based (complex to configure) | Built-in TLS encryption, certificates |
| Platform | Windows only | Cross-platform capable |
| Firewall traversal | Difficult (DCOM) | Straightforward (TCP 4840 default) |
| PLC support | Modicon families | Modicon families |
| Symbolic access | ✅ (Unity Pro XVM) | ✅ |
| Future roadmap | Maintenance mode | Active development |
| Modern IT/OT integration | Limited | ✅ (IIoT, cloud connectivity) |
Recommendation for existing OFS installations: OFS 3.63 SP3 is fully functional and supported. There is no urgent need to migrate immediately. Plan migration to OPC UA Server Expert during the next major system upgrade or when adding new SCADA capabilities that benefit from OPC UA.
Recommendation for new installations: Use EcoStruxure OPC UA Server Expert for all new projects. OPC UA is the modern standard with better security, easier firewall traversal, and an active development roadmap.
Frequently Asked Questions
Does OFS 3.63 SP3 require a license? From OFS 3.63 SP2 onwards, the license check for standard operation has been removed according to community reports. The driver mode (for specific communication driver options) still has licensing requirements. Verify current licensing requirements with Schneider Electric or your AVEVA representative for your specific deployment scenario.
Can OFS run on a virtual machine? Yes. OFS runs on standard Windows virtual machines (VMware, Hyper-V, etc.) without issues. Ensure the VM has stable network connectivity to both the PLC network and the SCADA client network.
Can multiple OPC clients connect to the same OFS instance simultaneously? Yes. OFS supports up to 300 simultaneous OPC connections (SP3 limit). Multiple SCADA stations, historian servers, and HMI clients can all connect to a single OFS instance.
What is the difference between OFS and a generic Modbus OPC server (Kepware, Matrikon)? A generic Modbus OPC server reads Modbus register addresses (%MW100, etc.) and requires manual mapping. OFS with Unity Pro integration provides symbolic variable access — using the actual variable names from the PLC program (%MW100 becomes Motor1.Speed). This dramatically reduces configuration errors and simplifies SCADA tag database maintenance.
Is OFS compatible with M580 PLCs? Yes. M580 is supported via the Unity protocol path, same as M340 and Quantum.
Summary
OPC Factory Server 3.63 SP3 remains the standard OPC DA gateway for Modicon PLC data in AVEVA and Schneider Electric ecosystems. Its symbolic variable access for Unity Pro / EcoStruxure Control Expert projects is a significant productivity advantage over generic Modbus OPC servers, and its support for all Modicon PLC families — from legacy TSX Micro through current M580 — makes it indispensable for mixed-generation installations.
For new projects, EcoStruxure OPC UA Server Expert is the strategic direction. For existing OFS installations, SP3 provides important security hardening and Windows 11/Server 2022 compatibility that justifies upgrading from earlier SP releases.
For licensing assistance or OFS configuration support, contact our team via Telegram: t.me/DoCrackMe
Related articles: EcoStruxure OPC UA Server Expert vs OFS — Migration Guide | Modicon M340 to SCADA via OFS — Step-by-Step Tutorial | OFS DCOM Configuration for Remote OPC Clients — Troubleshooting Guide
