Solved by pietern in post #7 
              
              
                @alchemi5t If you’re running processes on two machines, they won’t be able to talk if you’re using localhost (127.0.0.1) for the address of rank 0 in the initialization method. It must be an IP that’s reachable from all other ranks. In the example here, rank 1 was trying to connect to rank 0 over 12…