public boolean sslEnabled() {
        final String listenerSecurityProtocolMap = brokerConfig.getProperty(SocketServerConfigs.LISTENER_SECURITY_PROTOCOL_MAP_CONFIG);
        if (listenerSecurityProtocolMap == null)
            return false;
        return listenerSecurityProtocolMap.contains(":SSL") || listenerSecurityProtocolMap.contains(":SASL_SSL");
    }
Get the brokers whose state match the given predicate.

@return the set of {@link BrokerServer} instances with states that match the predicate;
        never null but possibly empty
connect/runtime/src/test/java/org/apache/kafka/connect/util/clusters/EmbeddedKafkaCluster.java