From the MTA's website:

QUOTE
Weekend Busing - October 23-24 - Port  Jefferson Branch

The MTA Long Island Rail Road’s Port Jefferson Branch will be affected  by a track work program during the weekend of October 23 and 24. From 2:13  AM, Saturday, October 23 through 2:20 AM, Sunday, October 24, buses and  vans will be substituted for trains between Hicksville and Huntington as resurfacing work is completed on an important interlocking in the Syosset  area. Customers can expect up to 40 minutes additional travel time.

Eastbound

Eastbound trains will terminate at Hicksville.

Customers traveling to Syosset, Cold Spring Harbor or Huntington will  transfer to buses or vans at Hicksville to complete their trips.

Customers traveling to stations Greenlawn through Port Jefferson will  board express buses or vans at Hicksville to complete their trips.

Customers at Syosset and Cold Spring Harbor and intermediate station  travelers will board local buses or vans.

Customers at Huntington will use regularly scheduled train service  for stations further east.

Westbound

Customers from stations Port Jefferson through Greenlawn will board  regularly scheduled trains at their stations and transfer at Huntington  for buses or vans and transfer to trains at Hicksville to complete their  trips.

Customers at Syosset, Cold Spring Harbor and Huntington will board  buses or vans at their stations and transfer to trains at Hicksville  to complete their trips.

Customers traveling to intermediate stations Huntington through Hicksville  will board local buses at Huntington.

Buses will depart up to 20 minutes later than regularly scheduled  trains.