Free OPC SERVER

Advosol offers a number of simulation and sample servers, usually as part of a toolkit or component evaluation (requires registration). Supported specifications include DA 2, DA 3, HDA and XML-DA.
ADVOSOL

Freeware simulator server for DA 2.0 and 1.0. Usefully shows list of clients and groups, plus an activity log.
DSxP

Evaluation version of a combined OPC server and client package, including several I/O drivers. Very flexible, but user interface is sometimes confusing. Includes support for a proprietary protocol, offering a subset of OPC Data Access functionality, which uses XML data packets sent over HTTP.
IOServer

Time-limited demo download of leading DA server bundle, incorporating over 80 communications drivers. Supports DDE and SuiteLink for legacy applications. Also includes a useful client program (see clients). Now DA 3.0 compliant.
Kepware

Various MatrikonOPC servers are available as free time-limited downloads, requiring restarting after two hours continuous use. All MatrikonOPC servers also have a DDE server capability.
Matrikon

Free demo server. Version 4.10 adds XML-DA to the existing DA and AE support. The XML-DA server may run standalone, or integrated with Apache or IIS.
Softing

OPCSvr.zip is a simulation server supporting Data Access 2. It has some useful diagnostic aids: the user may control the profiles of the simulated data points, and all OPC interface calls are displayed in a logging window. Also available is a demo server for Historical Data Access.
WinTECH Software

Free OPC Clients

Advosol offers a number of simulation and sample servers, usually as part of a toolkit or component evaluation (requires registration). Supported specifications include DA 2, DA 3, HDA and XML-DA.
ADVOSOL

Time-limited demo of DA 2 and DA 3 server and client combination that supports OPC tunnelling, aggregation, and bridging. Also offers TCP and DDE client and server, plus scripted read/write connections to ODBC databases and MATLAB.
Cogent Real-Time Systems

Time-limited demo version of a Visual Basic application for bidirectional data transfer between databases and OPC servers. Source available at extra cost.
Eldridge Engineering

Simple test client, originally intended for checking compatibility of servers with the company's PID tuning product.
Expertune - OPC Client

Evaluation version of an OPC server which also includes client functionality.
IOServer

Comprehensive yet easy to use trending tool. OPC DA is used to gather real-time data from any OPC server, while OPC HDA may also be used for historical data retrieval.
Matrikon - OPC Trending Tool

Greatly simplifies the task of importing live OPC data into Office applications (e.g. Excel) and ODBC databases. Free time-limited download available for evaluation.
Rensen Information Services

Flexible and easy to use client. Version 4.10 adds integrated XML-DA support to the existing support for DA and AE.
Softing