First use the following command to check whether the port number is enabled

sudo netstat -ntlp

If you don’t find the port number you want to connect to, go to core-site.xml to see if you have this port number.

I don’t deserve 8020. I haven’t been connected with 8020 for a long time.

<property>
        <name>fs.defaultFS</name>
        <value>hdfs://hadoop131:9820</value>
</property>

You can change the port number of the connection to your own