> But ForkingPickler could be used in multiprocessing.connection, > couldn't it? I suppose so. Note that the way a connection handle is transferred between existing processes is unnecessarily inefficient on Windows. A background server thread (one per process) has to be started and the receiving process must connect back to the sending process to receive its duplicate handle. There is a simpler way to do this on Windows. The sending process duplicates the handle, and the receiving process duplicates that second handle using DuplicateHandle() and the DUPLICATE_CLOSE_SOURCE flag. That way no server thread is necessary on Windows. I got this to work recently for pickling references to file handles for mmaps on. (A server thread would still be necessary on Unix.)