When you try to connect to database using sqlplus with collaboration of easy connect feature, you may get a bit confused by not having successfully logged in when you don't enter user's password inline. In other case (with inline password), the following command will be ok :
sqlplus username/password@IP_OR_HOSTNAME:PORT/SERVICE_NAME
and following will not:
sqlplus username@IP_OR_HOSTNAME:PORT/SERVICE_NAME
In such situation you'll get sqlplus breaf help text. The workaround is using single or double quotes with escape symbols :
sqlplus username@\"IP_OR_HOSTNAME:PORT/SERVICE_NAME\"
or
sqlplus username@\'IP_OR_HOSTNAME:PORT/SERVICE_NAME\'
You may catch errors ORA-12504 ORA-01017 if you place quotes in wrong place. For example, you'll get ORA-01017 in the following case :
sqlplus \'username@IP_OR_HOSTNAME:PORT/SERVICE_NAME\'
or ORA-12504 when you'll not use escape quoting, like in :
sqlplus username@"IP_OR_HOSTNAME:PORT/SERVICE_NAME"
Good luck !
