I am new to OPC-UA and Eclipse Milo and I am trying to construct a client that can connect to the OPC-UA server of a machine we have just acquired.
I have been able to set up a simple OPC-UA server on my laptop by using this python tutorial series: https://www.youtube.com/watch?v=NbKeBfK3pfk. Additionally, I have been able to use the Eclipse Milo examples to run the subscription example successfully to read some values from this server.
However, I have been having difficulty connecting to the OPC-UA server of the machine we have just received. I have successfully connected to this server using the UaExpert client, but we want to build our own client using Eclipse Milo. I can see that some warnings come up when using UaExpert to connect to the server which appear to give clues about the issue but I have too little experience in server-client communications/OPC-UA and would appreciate some help. I will explain what happens when I use the UaExpert client as I have been using this to try and diagnose what is going on.
I notice that when I first launch UaExpert I get the following errors which could be relevant:
Discovery FindServersOnNetwork on opc.tcp://localhost:4840 failed (BadTimeout), falling back to FindServers
Discovery FindServers on opc.tpc://localhost:4840 failed (BadTimeout)
Discovery GetEndpoints on opc.tcp://localhost:4840 failed
I am really new to networking so not sure exactly what this means.
I will outline the process I have followed when trying to get the SubscriptionExample of Eclipse Milo working with this machine's server. Firstly, I change the getEndpointUrl() method to the ip address of the device we are using: return "opc.tcp://11.23.1.1:4840". I can successfully ping the device using ping 11.23.1.1 from my laptop. When I try to run the SubscriptionExample with this address I get the following error:
[NonceUtilSecureRandom] INFO o.e.m.o.stack.core.util.NonceUtil - SecureRandom seeded in 0ms.
18:36:23.879 [main] ERROR o.e.m.e.client.ClientExampleRunner - Error running client example: java.net.UnknownHostException: br-automation
java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
at java.util.concurrent.CompletableFuture.reportGet(Unknown Source)
at java.util.concurrent.CompletableFuture.get(Unknown Source)
at org.eclipse.milo.examples.client.SubscriptionExample.run(SubscriptionExample.java:50)
at org.eclipse.milo.examples.client.ClientExampleRunner.run(ClientExampleRunner.java:120)
at org.eclipse.milo.examples.client.SubscriptionExample.main(SubscriptionExample.java:42)
Caused by: java.net.UnknownHostException: br-automation
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getByName(Unknown Source)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:148)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:145)
at java.security.AccessController.doPrivileged(Native Method)
at io.netty.util.internal.SocketUtils.addressByName(SocketUtils.java:145)
at io.netty.resolver.DefaultNameResolver.doResolve(DefaultNameResolver.java:43)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:63)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:55)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:57)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:32)
at io.netty.resolver.AbstractAddressResolver.resolve(AbstractAddressResolver.java:108)
at io.netty.bootstrap.Bootstrap.doResolveAndConnect0(Bootstrap.java:200)
at io.netty.bootstrap.Bootstrap.access$000(Bootstrap.java:46)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:180)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:166)
at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:577)
at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:551)
at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:490)
at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:615)
at io.netty.util.concurrent.DefaultPromise.setSuccess0(DefaultPromise.java:604)
at io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:104)
at io.netty.channel.DefaultChannelPromise.trySuccess(DefaultChannelPromise.java:84)
at io.netty.channel.AbstractChannel$AbstractUnsafe.safeSetSuccess(AbstractChannel.java:984)
at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:504)
at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:417)
at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:474)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at java.lang.Thread.run(Unknown Source)
18:36:23.881 [ForkJoinPool.commonPool-worker-1] ERROR o.e.m.e.client.ClientExampleRunner - Error running example: java.net.UnknownHostException: br-automation
java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
at java.util.concurrent.CompletableFuture.reportGet(Unknown Source)
at java.util.concurrent.CompletableFuture.get(Unknown Source)
at org.eclipse.milo.examples.client.SubscriptionExample.run(SubscriptionExample.java:50)
at org.eclipse.milo.examples.client.ClientExampleRunner.run(ClientExampleRunner.java:120)
at org.eclipse.milo.examples.client.SubscriptionExample.main(SubscriptionExample.java:42)
Caused by: java.net.UnknownHostException: br-automation
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getByName(Unknown Source)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:148)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:145)
at java.security.AccessController.doPrivileged(Native Method)
at io.netty.util.internal.SocketUtils.addressByName(SocketUtils.java:145)
at io.netty.resolver.DefaultNameResolver.doResolve(DefaultNameResolver.java:43)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:63)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:55)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:57)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:32)
at io.netty.resolver.AbstractAddressResolver.resolve(AbstractAddressResolver.java:108)
at io.netty.bootstrap.Bootstrap.doResolveAndConnect0(Bootstrap.java:200)
at io.netty.bootstrap.Bootstrap.access$000(Bootstrap.java:46)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:180)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:166)
at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:577)
at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:551)
at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:490)
at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:615)
at io.netty.util.concurrent.DefaultPromise.setSuccess0(DefaultPromise.java:604)
at io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:104)
at io.netty.channel.DefaultChannelPromise.trySuccess(DefaultChannelPromise.java:84)
at io.netty.channel.AbstractChannel$AbstractUnsafe.safeSetSuccess(AbstractChannel.java:984)
at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:504)
at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:417)
at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:474)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at java.lang.Thread.run(Unknown Source)
When using UaExpert, "opc.tcp://11.23.1.1:4840" is the address of the server that I input when adding a new server when using Custom Discovery. When I enter this, a device appears as a dropdown of this server called B&R Embedded OPC-UA Server as the OPC-UA server is hosted on a B&R device in the machine. When I select this device to connect to, I get the following message:
The hostname of the discovery URL used to call GetEndpoints (br-automation) was replaced by the hostname used to call FindServers (11.23.1.1). Do you also want to replace the hostnames of the EndpointURLs with this hostname?
I have to accept this message for the server to be found, but I am confused exactly what is going on. I assume there is a difference in the endpoint used to find the server and the endpoint used for something else? I have found the resources online very difficult to understand. In the UaExpert logs there are three lines of logs in a row which report "Adding Url: ocp.tcp://br-automation:4840". It also then reports the endpoint: "ocp.tcp://br-automation:4840", the application Uri and the security policy (none). If I try change the address in the client's getEndpointUrl method to ocp.tcp://br-automation:4840 then I get the following error:
[main] INFO o.e.m.opcua.sdk.client.OpcUaClient - Eclipse Milo OPC UA Client SDK version: 0.4.3-SNAPSHOT
18:37:46.035 [main] ERROR o.e.m.e.client.ClientExampleRunner - Error getting client: java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
org.eclipse.milo.opcua.stack.core.UaException: java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
at org.eclipse.milo.opcua.sdk.client.OpcUaClient.lambda$create$1(OpcUaClient.java:204)
at java.util.Optional.orElseGet(Unknown Source)
at org.eclipse.milo.opcua.sdk.client.OpcUaClient.create(OpcUaClient.java:204)
at org.eclipse.milo.opcua.sdk.client.OpcUaClient.create(OpcUaClient.java:201)
at org.eclipse.milo.examples.client.ClientExampleRunner.createClient(ClientExampleRunner.java:73)
at org.eclipse.milo.examples.client.ClientExampleRunner.run(ClientExampleRunner.java:94)
at org.eclipse.milo.examples.client.SubscriptionExample.main(SubscriptionExample.java:42)
Caused by: java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
at java.util.concurrent.CompletableFuture.reportGet(Unknown Source)
at java.util.concurrent.CompletableFuture.get(Unknown Source)
at org.eclipse.milo.opcua.sdk.client.OpcUaClient.create(OpcUaClient.java:180)
... 4 common frames omitted
Caused by: java.net.UnknownHostException: br-automation
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getByName(Unknown Source)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:148)
at io.netty.util.internal.SocketUtils$8.run(SocketUtils.java:145)
at java.security.AccessController.doPrivileged(Native Method)
at io.netty.util.internal.SocketUtils.addressByName(SocketUtils.java:145)
at io.netty.resolver.DefaultNameResolver.doResolve(DefaultNameResolver.java:43)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:63)
at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:55)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:57)
at io.netty.resolver.InetSocketAddressResolver.doResolve(InetSocketAddressResolver.java:32)
at io.netty.resolver.AbstractAddressResolver.resolve(AbstractAddressResolver.java:108)
at io.netty.bootstrap.Bootstrap.doResolveAndConnect0(Bootstrap.java:200)
at io.netty.bootstrap.Bootstrap.access$000(Bootstrap.java:46)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:180)
at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:166)
at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:577)
at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:551)
at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:490)
at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:615)
at io.netty.util.concurrent.DefaultPromise.setSuccess0(DefaultPromise.java:604)
at io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:104)
at io.netty.channel.DefaultChannelPromise.trySuccess(DefaultChannelPromise.java:84)
at io.netty.channel.AbstractChannel$AbstractUnsafe.safeSetSuccess(AbstractChannel.java:984)
at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:504)
at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:417)
at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:474)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at java.lang.Thread.run(Unknown Source)
I don't know if this is enough information to diagnose the problem, but I would appreciate any help on how I can get the Eclipse Milo server to perform the same process and connect to the machine's server.