.. function:: Pipe([duplex])

Returns a pair ``(conn1, conn2)`` of :class:`Connection` objects representing

the ends of a pipe.

Returns a pair ``(conn1, conn2)`` of

:class:`~multiprocessing.connection.Connection` objects representing the

ends of a pipe.

If *duplex* is ``True`` (the default) then the pipe is bidirectional. If

*duplex* is ``False`` then the pipe is unidirectional: ``conn1`` can only be

Connection Objects

~~~~~~~~~~~~~~~~~~

.. currentmodule:: multiprocessing.connection

Connection objects allow the sending and receiving of picklable objects or

strings. They can be thought of as message oriented connected sockets.

Connection objects are usually created using :func:`Pipe` -- see also

Connection objects are usually created using

:func:`Pipe <multiprocessing.Pipe>` -- see also

:ref:`multiprocessing-listeners-clients`.

.. class:: Connection

Synchronization primitives

~~~~~~~~~~~~~~~~~~~~~~~~~~

.. currentmodule:: multiprocessing

Generally synchronization primitives are not as necessary in a multiprocess

program as they are in a multithreaded program. See the documentation for

:mod:`threading` module.

:synopsis: API for dealing with sockets.

Usually message passing between processes is done using queues or by using

:class:`~multiprocessing.Connection` objects returned by

:class:`~Connection` objects returned by

:func:`~multiprocessing.Pipe`.

However, the :mod:`multiprocessing.connection` module allows some extra

.. function:: Client(address[, family[, authkey]])

Attempt to set up a connection to the listener which is using address

*address*, returning a :class:`~multiprocessing.Connection`.

*address*, returning a :class:`~Connection`.

The type of the connection is determined by *family* argument, but this can

generally be omitted since it can usually be inferred from the format of

.. method:: accept()

Accept a connection on the bound socket or named pipe of the listener

object and return a :class:`~multiprocessing.Connection` object. If

authentication is attempted and fails, then

object and return a :class:`~Connection` object.

If authentication is attempted and fails, then

:exc:`~multiprocessing.AuthenticationError` is raised.

.. method:: close()

For both Unix and Windows, an object can appear in *object_list* if

it is

* a readable :class:`~multiprocessing.Connection` object;

* a readable :class:`~multiprocessing.connection.Connection` object;

* a connected and readable :class:`socket.socket` object; or

* the :attr:`~multiprocessing.Process.sentinel` attribute of a

:class:`~multiprocessing.Process` object.

Authentication keys

~~~~~~~~~~~~~~~~~~~

When one uses :meth:`Connection.recv <multiprocessing.Connection.recv>`, the

When one uses :meth:`Connection.recv <Connection.recv>`, the

data received is automatically

unpickled. Unfortunately unpickling data from an untrusted source is a security

risk. Therefore :class:`Listener` and :func:`Client` use the :mod:`hmac` module

unpickled. Unfortunately unpickling data from an untrusted source is a security

risk. Therefore :class:`Listener` and :func:`Client` use the :mod:`hmac` module

to provide digest authentication.

An authentication key is a byte string which can be thought of as a