Replace assert with runtime checks in TcpMessageDecoder

[Copilot]

Java assertions are disabled by default in production JVMs, meaning invalid message types in TcpMessageDecoder were silently accepted rather than rejected. All four decode methods now throw UaException(Bad_TcpMessageTypeInvalid) when the message type or chunk type doesn't match expectations.

Changes

• TcpMessageDecoder: Replaced assert in all four decode methods (decodeHello, decodeAcknowledge, decodeError, decodeReverseHello) with explicit runtime checks:

// Before
assert (messageType == MessageType.Hello && chunkType == 'F');

// After
if (messageType != MessageType.Hello || chunkType != 'F') {
    throw new UaException(
        StatusCodes.Bad_TcpMessageTypeInvalid,
        "unexpected MessageType/chunkType: " + messageType + "/" + chunkType);
}

This is consistent with how message type validation is handled elsewhere in the transport layer (e.g., UascServerHelloHandler, OpcTcpReverseConnectTransport).

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• repo.eclipse.org
  • Triggering command: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/17.0.18-8/x64/bin/java /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/17.0.18-8/x64/bin/java --enable-native-access=ALL-UNNAMED -classpath /usr/share/apache-maven-3.9.13/boot/plexus-classworlds-2.9.0.jar -Dclassworlds.conf=/usr/share/apache-maven-3.9.13/bin/m2.conf -Dmaven.home=/usr/share/apache-maven-3.9.13 -Dlibrary.jansi.path=/usr/share/apache-maven-3.9.13/lib/jansi-native -Dmaven.multiModuleProjectDirectory=/home/REDACTED/work/milo/milo org.codehaus.plexus.classworlds.launcher.Launcher -q spotless:apply -pl opc-ua-stack/stack-core (dns block)
  • Triggering command: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/17.0.18-8/x64/bin/java /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/17.0.18-8/x64/bin/java --enable-native-access=ALL-UNNAMED -classpath /usr/share/apache-maven-3.9.13/boot/plexus-classworlds-2.9.0.jar -Dclassworlds.conf=/usr/share/apache-maven-3.9.13/bin/m2.conf -Dmaven.home=/usr/share/apache-maven-3.9.13 -Dlibrary.jansi.path=/usr/share/apache-maven-3.9.13/lib/jansi-native -Dmaven.multiModuleProjectDirectory=/home/REDACTED/work/milo/milo org.codehaus.plexus.classworlds.launcher.Launcher -q clean compile -pl opc-ua-stack/stack-core (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)