The nearest mainland port is Bensersiel. From Jever, take the train to Esens and change to a bus for Bensersiel (€10.20, 45 minutes). From Emden, take the train to Norden and change to a bus for Bensersiel (€16.70, 1½ hours). Check connections on www.bahn.de before setting out.
The Langeoog ferry shuttles between Bensersiel and Langeoog around five times daily.