Design/CPN has interface called COMMS/CPN [5]. It allows to communicate with simulator while Petri net is being simulated. It is a message passing interface with small set of functions that allow to establish connection, send and receive messages. The functions should be called from Standard ML code being part of Petri net model (e.g. guards). There is Java/CPN interface, that facilitates establishing communication with COMMS/CPN from Java software. The newer CPN/Tools has two kinds of interfaces forming Access/CPN framework [17]. The first one, available for Standard ML and more tightly connected with the model is designed with state space analysis in mind. It is worth mentioning, that this interface is meant to be formalism independent, not strictly connected to TCPN. The second part of Access/CPN is Java CPN Model Interface. It allows to create or import model created using CPN Tools. It also supports TCP/IP based communication with running simulator.