java.net.ConnectException: Connection refused: no further information at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[na:1.8.0_352] at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:716) ~[na:1.8.0_352] at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:337) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:776) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.87.Final.jar:4.1.87.Final] at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.87.Final.jar:4.1.87.Final] at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.87.Final.jar:4.1.87.Final] at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.87.Final.jar:4.1.87.Final] at java.lang.Thread.run(Thread.java:750) [na:1.8.0_352]

这个错误通常表示您的Java应用程序无法连接到目标主机或端口。可能有多种原因导致这个问题，比如网络连接问题、目标主机或端口未启动、防火墙或网络代理等。您可以尝试先检查网络连接是否正常，然后再检查目标主机或端口是否已启动，并确保您的防火墙或网络代理已正确配置。如果问题仍然存在，您可以尝试使用Java Socket API手动连接目标主机或端口以了解更多详细信息。