Backup neo4j server ubuntu

Hi I'm hanme and super super new in neo4j.

I've installed neo4j (4.1.0 enterprise version) on AWS EC2 ubuntu server
and tried to do 'backup' with my small dataset.

when I run
bin/ sudo neo4j-admin backup --from=localhost --database=neo4j --backup-dir=/var/lib/neo4j/data/dumps --pagecache=4G

I meet this message : Execution of backup failed. port out of range:-1

I cannot just understand what this message says. i guess this might be a conf problem or something else

from stack overflow, they said me to fix port number but i could not figure out what exactly to change in neo4j.conf file

Is anybody who had similar problem?

please help me.

Thank you in advance