Milo: Connect to (public) OPC-UA-Server - eclipse

Question

First of all: I'm a newbie to OPCUA. :)
I'm trying to connect an Milo Client to our Server but don't really understand whats going wrong. The sample Client and Server work fine together, but when I try to connect the client sample with one of the public OPC-UA-Test-Servers I get those exceptions:
15:48:34.729 [ua-netty-event-loop-0] DEBUG
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientAcknowledgeHandler
- Sent Hello message on channel=[id: 0xc22800c2, L:/10.22.19.217:58947 - R:opcua.demo-this.com/52.233.134.134:51210]. 15:48:34.729 [ua-netty-event-loop-0] WARN io.netty.channel.DefaultChannelPipeline -
An exceptionCaught() event was fired, and it reached at the tail of
the pipeline. It usually means the last handler in the pipeline did
not handle the exception. java.io.IOException: An existing connection
was forcibly closed by the remote host at
sun.nio.ch.SocketDispatcher.read0(Native Method) at
sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43) at
sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223) at
sun.nio.ch.IOUtil.read(IOUtil.java:192) at
sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380) at
io.netty.buffer.PooledUnsafeDirectByteBuf.setBytes(PooledUnsafeDirectByteBuf.java:221)
at
io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:898)
at
io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:242)
at
io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:119)
at
io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:528)
at
io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:485)
at
io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:399)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:371) at
io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:112)
at java.lang.Thread.run(Thread.java:745) 15:48:39.612
[ForkJoinPool.commonPool-worker-1] DEBUG
org.eclipse.milo.opcua.stack.client.ClientChannelManager - Channel
bootstrap failed: timed out waiting for acknowledge
org.eclipse.milo.opcua.stack.core.UaException: timed out waiting for
acknowledge at
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientAcknowledgeHandler.lambda$startHelloTimeout$4(UaTcpClientAcknowledgeHandler.java:156)
at
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientAcknowledgeHandler$$Lambda$27/469017260.run(Unknown
Source) at
io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:581)
at
io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:655)
at
io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:367)
at java.lang.Thread.run(Thread.java:745) 15:48:39.613 [main] ERROR
org.eclipse.milo.examples.client.ClientExampleRunner - Error running
example: UaException: status=Bad_Timeout, message=timed out waiting
for acknowledge java.util.concurrent.ExecutionException: UaException:
status=Bad_Timeout, message=timed out waiting for acknowledge at
java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
at
java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1887)
at
org.eclipse.milo.examples.client.ClientExampleRunner.createClient(ClientExampleRunner.java:56)
at
org.eclipse.milo.examples.client.ClientExampleRunner.run(ClientExampleRunner.java:103)
at
org.eclipse.milo.examples.client.BrowseExample.main(BrowseExample.java:40)
Caused by: org.eclipse.milo.opcua.stack.core.UaException: timed out
waiting for acknowledge at
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientAcknowledgeHandler.lambda$startHelloTimeout$4(UaTcpClientAcknowledgeHandler.java:156)
at
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientAcknowledgeHandler$$Lambda$27/469017260.run(Unknown
Source) at
io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:581)
at
io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:655)
at
io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:367)
at java.lang.Thread.run(Thread.java:745) 15:48:42.842
[threadDeathWatcher-2-1] DEBUG io.netty.buffer.PoolThreadCache - Freed
2 thread-local buffer(s) from thread: ua-netty-event-loop-0
I took the sample-Code and removed the Certificate/Keypair and changed the URL to opc.tcp://opcua.demo-this.com:51210/UA/SampleServer since the public server doesn't need authorization:
SecurityPolicy securityPolicy = clientExample.getSecurityPolicy();
EndpointDescription[] endpoints = UaTcpStackClient.getEndpoints("opc.tcp://opcua.demo-this.com:51210/UA/SampleServer").get();
EndpointDescription endpoint = Arrays.stream(endpoints)
.filter(e -> e.getSecurityPolicyUri().equals(securityPolicy.getSecurityPolicyUri()))
.findFirst().orElseThrow(() -> new Exception("no desired endpoints returned"));
logger.info("Using endpoint: {} [{}]", endpoint.getEndpointUrl(), securityPolicy);
loader.load();
OpcUaClientConfig config = OpcUaClientConfig.builder()
.setApplicationName(LocalizedText.english("eclipse milo opc-ua client"))
.setApplicationUri("urn:eclipse:milo:examples:client")
//.setCertificate(loader.getClientCertificate())
//.setKeyPair(loader.getClientKeyPair())
.setEndpoint(endpoint)
.setIdentityProvider(clientExample.getIdentityProvider())
.setRequestTimeout(uint(5000))
.build();
return new OpcUaClient(config);
What am I missing?
Greetings and thanks in advance :)

Answer 1

Buried in that stack trace is the real problem: UaException: timed out waiting for acknowledge.
Maybe your firewall or network setup is blocking it, or maybe the server didn't send it back, but the problem is that the client never received the Acknowledge message in response to its Hello.
FWIW, I can run the ReadExample against that public server with no issue. In ReadExample I overrode getSecurityPolicy() and returned SecurityPolicy.None and in ClientExampleRunner just replaced the endpoint URL.