Java OPC UA org.eclipse.milo.examples.client.ClientExampleRunner错误

我正在使用org.eclipse.milo库与java中的OPC UA服务器通信。我能够与服务器通信并获取数据。但在日志中，我可以看到以下与OPC UA服务器之间的通信异常

我也在使用Quartz API。以下是例外

ERROR [org.eclipse.milo.examples.client.ClientExampleRunner] (null_Worker-86) Error running example: java.lang.IllegalStateException: executor not accepting a task: java.util.concurrent.ExecutionException: java.lang.IllegalStateException: executor not accepting a task
    at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
    at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1895)
    at org.eclipse.milo.examples.client.ClientExampleRunner.createClient(ClientExampleRunner.java:54)
    at org.eclipse.milo.examples.client.ClientExampleRunner.run(ClientExampleRunner.java:93)
    at com.winjit.scheduler.OpcClientScheduler.execute(OpcClientScheduler.java:44)
    at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
    at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)
Caused by: java.lang.IllegalStateException: executor not accepting a task
    at io.netty.resolver.AddressResolverGroup.getResolver(AddressResolverGroup.java:58)
    at io.netty.bootstrap.Bootstrap.doResolveAndConnect0(Bootstrap.java:200)
    at io.netty.bootstrap.Bootstrap.access$000(Bootstrap.java:49)
    at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:188)
    at io.netty.bootstrap.Bootstrap$1.operationComplete(Bootstrap.java:174)
    at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:514)
    at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:488)
    at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:427)
    at io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:111)
    at io.netty.channel.DefaultChannelPromise.trySuccess(DefaultChannelPromise.java:82)
    at io.netty.channel.AbstractChannel$AbstractUnsafe.safeSetSuccess(AbstractChannel.java:897)
    at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:508)
    at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:419)
    at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:478)
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:418)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:454)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:873)
    at java.lang.Thread.run(Thread.java:745)