Open-source OPC UA client and server library for .NET (deprecated) and .NET Core based on IEC 62541. Available as source files, a demo client and a demo server. Tested and commercially used in industrial applications with commercial vendors' UA servers and clients.

Available as a nuget package for .NET Core (1.0.8): https://www.nuget.org/packages/nauful-LibUA-core

• Fully supported OPC UA core client and OPC UA server specification.
• OPC UA binary protocol with chunking.
• Security profiles None, Basic128Rsa15, Basic256, Basic256Sha256, Aes128Sha256RsaOaep (.NET Standard only) and Aes256Sha256RsaPss (.NET Standard only).
• Optimized memory buffers for encoding/decoding large and complex structures to/from raw bytes.
• Support for all message types, node types, and default address space from the UA specification.
• Support for signing and encrypted security profiles.
• Anonymous, user/pass and certificate-based authentication.
• Sessions, subscriptions (data change notifications and custom notifications), custom events and alarming.
• Extendable server address space with hooks for client requests for access control, read handlers, write handlers, etc.
• Support for reads, writes, updates, historical data and aggregation.
• Server instances have low overhead: tested with hundreds of clients performing simultaneous historical reads, data change notification subscriptions and real-time writes.

• .NET Standard 2.0
• .NET 4.8 is deprecated and not actively maintained.

Free for commercial use under the Apache License 2.0. Please give credit if you find this source useful.

The demo client and server applications can create self-signed certificates with sufficient fields for most usage. Remember to move these to the trusted directory on a server when connecting to a server for the first time.