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Eclipse Milo is an open-source implementation of OPC UA (IEC 62541) for Java. It includes an OPC UA stack and client and server SDKs. Milo targets OPC UA 1.05 and runs on Java 17 or later.

This user guide is being built for Milo 1.2.0-SNAPSHOT. Topic pages currently contain outlines and links to existing examples and guides. The 1.2.0 feature and migration guide is available for applications upgrading from 1.1.7.

Start here

• Getting started: dependencies, versions, and running the examples.
• OPC UA concepts: the vocabulary used throughout the guide.
• Your first client and your first server.

SDK guides

• Client SDK: connect, browse, read, write, subscribe, and call methods.
• Server SDK: configure a server, build its address space, and connect it to live data.
• Examples: runnable code and suggested learning paths.

Reference and operations

• Reference: data types, security policies, configuration, and feature topics.
• Capabilities and limitations.
• Troubleshooting, diagnostics and Wireshark, and deployment.
• Release notes.

Getting help

• Ask questions in GitHub Discussions.
• Report bugs in GitHub Issues.
• Report security issues privately as described in the security policy.
• The milo-dev mailing list and the milo tag on Stack Overflow have older discussions.

Contributing

Contributor resources link to build instructions, conventions, testing guidance, and architecture documentation in the source repository.