  Multiparty session types are a type system that can ensure the safety and
liveness of distributed peers via the global specification of their
interactions. To construct a global specification from a set of distributed
uncontrolled behaviours, this paper explores the problem of fully
characterising multiparty session types in terms of communicating automata. We
equip global and local session types with labelled transition systems (LTSs)
that faithfully represent asynchronous communications through unbounded
buffered channels. Using the equivalence between the two LTSs, we identify a
class of communicating automata that exactly correspond to the projected local
types. We exhibit an algorithm to synthesise a global type from a collection of
communicating automata. The key property of our findings is the notion of
multiparty compatibility which non-trivially extends the duality condition for
binary session types.
