报错：Connection to node -1 could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)

报错背景：

启动kafka消费者之后出现这种报错，持续打印相同信息。

报错现象：

[root@master kafka_2.-1.1.]# /opt/kafka/kafka_2.-1.1./bin/kafka-console-consumer.sh --bootstrap-server master: --topic alarmHis
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/bigdata/app/.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/bigdata/app/bigdata-1.0-SNAPSHOT-jar-with-dependencies.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/opt/kafka/kafka_2.-1.1./libs/slf4j-log4j12-1.7..jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
[-- ::,] WARN [Consumer clientId=consumer-, groupId=console-consumer-] Connection to node - could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)
[-- ::,] WARN [Consumer clientId=consumer-, groupId=console-consumer-] Connection to node - could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)
[-- ::,] WARN [Consumer clientId=consumer-, groupId=console-consumer-] Connection to node - could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)
[-- ::,] WARN [Consumer clientId=consumer-, groupId=console-consumer-] Connection to node - could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)
[-- ::,] WARN [Consumer clientId=consumer-, groupId=console-consumer-] Connection to node - could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)

报错原因：

不明。

报错解决：