Hi, I'm connecting two MPI applications A and B using MPI_Comm_accept in A and MPI_Comm_connect in B. I would like to know a bit more about the behavior in case one application stops (say B): will a communication attempt (e.g. MPI_Send) from a process from A to a process from B crash? return an error? block? Is there a way for application A to notice that B has stopped in order to avoid communicating with it? Thanks. PS: by the way for whom is involved in the MPI forum, an MPI_Comm_iaccept in the MPI3 standard would have been useful. Something to keep in mind for the next version maybe ;) Matthieu Dorier PhD student at ENS Cachan Brittany and IRISA http://people.irisa.fr/Matthieu.Dorier