如何解决在BadHostUnknown
我是OPC-UA和Eclipse Milo的新手，我正在尝试构建一个可以连接到我们刚刚购买的计算机的OPC-UA服务器的客户端。
通过使用以下Python教程系列：https://www.youtube.com/watch?v=NbKeBfK3pfk，我已经能够在笔记本电脑上设置简单的OPC-UA服务器。另外，我已经能够使用Eclipse Milo示例成功运行订阅示例，以从该服务器读取一些值。
但是，连接到我们刚收到的机器的OPC-UA服务器时遇到了困难。我已经使用UaExpert客户端成功连接到该服务器，但是我们想使用Eclipse Milo构建自己的客户端。我可以看到使用UaExpert连接到服务器时出现了一些警告，这些警告似乎提供了有关此问题的线索，但是我在服务器-客户端通信/ OPC-UA方面的经验很少，希望能提供一些帮助。我将解释使用UaExpert客户端时发生的情况，因为我一直在尝试使用它来诊断正在发生的事情。
我注意到，当我第一次启动UaExpert时，遇到了以下可能相关的错误：
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
我真的是网络新手，所以不确定确切的含义。
我将概述在尝试使Eclipse Milo的SubscriptionExample与此机器的服务器一起工作时遵循的过程。首先，我将getEndpointUrl（）方法更改为我们正在使用的设备的IP地址：返回“ opc.tcp：//11.23.1.1：4840”。我可以使用便携式计算机上的ping 11.23.1.1成功ping设备。当我尝试使用该地址运行SubscriptionExample时，出现以下错误：
[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$2.run(ThreadExecutorMap.java:74)
at java.lang.Thread.run(Unknown Source)
使用UaExpert时，“ opc.tcp：//11.23.1.1：4840”是在使用“自定义发现”时添加新服务器时输入的服务器地址。当我输入此命令时，设备将显示为该服务器的下拉列表，称为B＆R嵌入式OPC-UA服务器，因为OPC-UA服务器托管在计算机中的B＆R设备上。当我选择要连接的设备时，会收到以下消息：
用于调用GetEndpoints（br-automation）的发现URL的主机名已替换为用于调用FindServers的主机名（11.23.1.1）。您是否还要用此主机名替换EndpointURL的主机名？
我必须接受此消息才能找到服务器，但是我对到底发生了什么感到困惑。我假设用于查找服务器的端点与用于其他用途的端点有所不同？我发现网上的资源很难理解。在UaExpert日志中，连续三行日志报告“正在添加网址：ocp.tcp：// br-automation：4840”。然后，它还报告端点：“ ocp.tcp：// br-automation：4840”，应用程序Uri和安全策略（无）。如果我尝试将客户端的getEndpointUrl方法中的地址更改为ocp.tcp：// br-automation：4840，则会收到以下错误：
[main] INFO o.e.m.opcua.sdk.client.OpcUaClient - Eclipse Milo OPC UA Client SDK version: 0.4.3-SNAPSHOT
18:37:46.035 [main] ERROR o.e.m.e.client.ClientExampleRunner - Error getting client: java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
org.eclipse.milo.opcua.stack.core.UaException: java.util.concurrent.ExecutionException: java.net.UnknownHostException: br-automation
at org.eclipse.milo.opcua.sdk.client.OpcUaClient.lambda$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)
我不知道这些信息是否足以诊断问题，但是对于如何使Eclipse Milo服务器执行相同的过程并连接到计算机的服务器方面的任何帮助，我将不胜感激。
解决方法
问题是运行客户端的计算机无法将主机名“ br-automation”解析为IP地址。
如果无法将服务器配置为返回IP地址，则解决方案是手动重建从GetEndpoints服务调用中获取的EndpointDescription，以便它们具有包含IP地址而不是IP地址的终结点URL。主机名。这是UaExpert在警告您替换主机名时在后台执行的操作。
您可以使用EndpointUtil#updateUrl来构建新的EndpointDescription，然后再将其传递给OpcUaClientConfig。
您可以使用服务器日志找到正确的主机名/ URL以连接服务器。 服务器日志启动后，它将打印所有有效的UR
,我们能够通过用主机IP和端口手动覆盖从OPC UA服务器返回的主机名来解决我们的问题。 （请参见try语句的第二行）
public class OpcUaConnection {
OpcUaClient client;
final int NAMESPACEINDEX = 6;
private static final AtomicLong clientHandles = new AtomicLong(1L);
public OpcUaConnection() {
try {
List<EndpointDescription> endpoints = DiscoveryClient.getEndpoints("opc.tcp://192.168.0.122:4840").get();
EndpointDescription configPoint = EndpointUtil.updateUrl(endpoints.get(0),"192.168.0.122",4840);
OpcUaClientConfigBuilder cfg = new OpcUaClientConfigBuilder();
cfg.setEndpoint(configPoint);
this.client = OpcUaClient.create(cfg.build());
client.connect().get();
} catch (Throwable ex) {
ex.printStackTrace();
}
}
希望这可以帮助其他人！
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