In this paper we consider a calculus of connectors that allows for the most general combination of synchronisation, non-determinism and buffering. According to previous results, this calculus is tightly related to a flavour of Petri nets with interfaces for composition, called Petri nets with boundaries. The calculus and the net version are equipped with equivalent bisimilarity semantics. Also the buffers (the net places) can be one-place (C/E nets) or with unlimited capacity (P/T nets). In the paper we investigate the idea of finding normal form representations for terms of this calculus, in the sense that equivalent (bisimilar) terms should have the same (isomorphic) normal form. We show that this is possible for finite state terms. The result is obtained by computing the minimal marking graph (when finite) for the net with boundaries corresponding to the given term, and reconstructing from it a canonical net and a canonical term.