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    Check if you don't have a VPN or something like this messing with your connection. Also, check Jenkins DNS configurations (try to start it with "--dns 8.8.8.8".

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java.net.UnknownHostException: opt	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)	at java.net.Socket.connect(Socket.java:589)	at java.net.Socket.connect(Socket.java:538)	at sun.net.ftp.impl.FtpClient.doConnect(FtpClient.java:957)	at sun.net.ftp.impl.FtpClient.tryConnect(FtpClient.java:917)	at sun.net.ftp.impl.FtpClient.connect(FtpClient.java:1012)	at sun.net.ftp.impl.FtpClient.connect(FtpClient.java:998)	at sun.net.www.protocol.ftp.FtpURLConnection.connect(FtpURLConnection.java:294)	at sun.net.www.protocol.ftp.FtpURLConnection.getInputStream(FtpURLConnection.java:393)	at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:557)	at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:526)	at org.apache.log4j.LogManager.(LogManager.java:127)	at org.slf4j.impl.Log4jLoggerFactory.(Log4jLoggerFactory.java:66)	at org.slf4j.impl.StaticLoggerBinder.(StaticLoggerBinder.java:72)	at org.slf4j.impl.StaticLoggerBinder.(StaticLoggerBinder.java:45)	at org.slf4j.LoggerFactory.bind(LoggerFactory.java:150)	at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:124)	at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:412)	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:357)	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:383)	at org.apache.kafka.common.security.JaasUtils.(JaasUtils.java:30)	at kafka.admin.ConsumerGroupCommand$ZkConsumerGroupService.(ConsumerGroupCommand.scala:135)	at kafka.admin.ConsumerGroupCommand$.main(ConsumerGroupCommand.scala:58)	at kafka.admin.ConsumerGroupCommand.main(ConsumerGroupCommand.scala)