@Override
        public void close() {
            if (principalBuilder instanceof Closeable)
                Utils.closeQuietly((Closeable) principalBuilder, "principal builder");
        }
Constructs a plaintext channel builder. ListenerName is non-null whenever
it's instantiated in the broker and null otherwise.
clients/src/main/java/org/apache/kafka/common/network/PlaintextChannelBuilder.java