Eclipse Milo

Milo is an open-source implementation of OPC UA (currently targeting 1.05). It includes a high-performance stack (channels, serialization, data structures, security) as well as client and server SDKs built on top of the stack.

Stack Overflow tag: milo

Mailing list: https://dev.eclipse.org/mailman/listinfo/milo-dev

Documentation

The Milo Wiki is the user guide. If you are new to Milo, start with Getting started, then build the tutorial server and a client that talks to it. The client and server guides continue from there. Examples lists the runnable programs in milo-examples.

Requirements

The repository pins its Java and Maven toolchain with mise:

mise install

If mise reports that the config is not trusted, review .mise.toml and run mise trust .mise.toml once. After installation, run Maven through mise exec -- so the pinned Java 17 and Maven versions are used.

Maven

Building Milo

Using JDK 17, run this from the project root:

mise exec -- mvn clean install

To maintain compatibility with Java 17 it is recommended that you build using JDK 17, however the library is runtime compatible with versions 17 and later (e.g. JDK 21, JDK 24).

Releases

Releases are published to Maven Central and snapshots to Sonatype.

OPC UA Client SDK

<dependency>
    <groupId>org.eclipse.milo</groupId>
    <artifactId>milo-sdk-client</artifactId>
    <version>1.1.6</version>
</dependency>

OPC UA Server SDK

<dependency>
    <groupId>org.eclipse.milo</groupId>
    <artifactId>milo-sdk-server</artifactId>
    <version>1.1.6</version>
</dependency>

The Wiki's server guides cover the sampling framework and access control, roles, and permissions (1.2.0 and later).

GDS Client (1.2.0 and later)

Registers an application with a Global Discovery Server, requests certificates through the Pull Model, and reads GDS trust lists. See the GDS client guide.

<dependency>
    <groupId>org.eclipse.milo</groupId>
    <artifactId>milo-sdk-client-gds</artifactId>
    <version>1.2.0-SNAPSHOT</version>
</dependency>

Referencing a SNAPSHOT release requires the Sonatype snapshot repository be added to your pom file:

<repository>
    <id>sonatype-snapshots</id>
    <url>https://central.sonatype.com/repository/maven-snapshots/</url>
    <releases><enabled>false</enabled></releases>
    <snapshots><enabled>true</enabled></snapshots>
</repository>

Public Demo Server

An internet-facing instance of this demo server is accessible at opc.tcp://milo.digitalpetri.com:62541/milo.

It accepts both unsecured and secured connections. All incoming client certificates are automatically trusted.

Authenticate anonymously or with one of the following credential pairs:

• User / password
  • roles: WellKnownRole_AuthenticatedUser
• UserA / password
  • roles: SiteA_Read, SiteA_Write
• UserB / password
  • roles: SiteB_Read, SiteB_Write
• SiteAdmin / password
  • roles: SiteA_Read, SiteB_Read
• SecurityAdmin / password
  • roles: WellKnownRole_SecurityAdmin

The code powering the demo server is available here: https://github.com/digitalpetri/opc-ua-demo-server