You need to copy the entire entry and change port


LISTENERMYSQLSERVERDSN =
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST= hostname of oracle database)(PORT=1522))
(ADDRESS=(PROTOCOL=ipc)(KEY=PNPKEY)))

SID_LIST_ =
(SID_LIST=
(SID_DESC=
(SID_NAME= mysqlserver)
(ORACLE_HOME = /u01/app/oracle/product/101)
(PROGRAM=hsodbc)
)
)