Exception in thread "main" NoNodeAvailableException[None of the configured nodes are available: [{#transport#-1}{1mGQG8lESjeXy_ONyt2FRQ}{192.168.0.139}{192.168.0.139:9300}]]
除了网上提到的常见问题，例如cluster.name，port不匹配（默认访问url端口是9200，但是连接端口是9300）之外，还要留意引进的transport的版本有没有问题。
找到安装目录下的日志F:elasticsearch-7.5.0-windows-x86_64elasticsearch-7.5.0logmy-application_server.json，有输出过下面的问题：
2020-02-15T00:18:53,334+08:00", "level": "WARN", "component": "o.e.t.TcpTransport", "cluster.name": "my-application", "node.name": "DESKTOP-R3BLRIN", "message": "exception caught on transport layer [Netty4TcpChannel{localAddress=/127.0.0.1:9300, remoteAddress=/127.0.0.1:11931}], closing connection", "cluster.uuid": "HXtKTVCFSTiibfJBiea7tw", "node.id": "9juaKZHLQCWgm0G9oIe_kw" ,
"stacktrace": ["java.lang.IllegalStateException: Received message from unsupported version: [6.2.4] minimal compatible version is: [6.8.0]",
默认是 elasticsearch_server.json
