Call From sandbox-hdp.hortonworks.com/172.18.0.2 to localhost:8020 failed on connection exception

Question

I use Hortonworks Sandbox HDP 2.6.5 and putty to use Linux shell. My OS is window10.

I put some JSON file on HDFS and I want to open this file with pyspark.

I use below python file on linux, typing "spark-submit example.py" on shell

from pyspark.sql import SparkSession

if __name__ == "main":
    spark = SparkSession.builder.appName('JSONRead').getOrCreate()

    jsonData = spark.read.json('hdfs://localhost/user/maria_dev/example.json')
    jsonData.printSchema()
    jsonData.createOrReplaceTempView('Users')

    userNames = spark.sql('SELECT _id, name, age, email, phone, gender, index from Users')

    spark.stop()

But I got this error message

"Call From sandbox-hdp.hortonworks.com/172.18.0.2 to localhost:8020 failed on connection exception"

I searched this problem on stackoverflow and people usually said name node is running different port or not run. But I don't know how to know name node's status and how to restart it.

I typed "sudo service hadoop-hdfs-namenode restart" But putty return "Unit hadoop-hdfs-namenode.service could not be found."

What can I do? Can you help me please?