diff --git a/mitogen/core.py b/mitogen/core.py
index 1f21173f..47355861 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -643,6 +643,9 @@ class Stream(BasicStream):
     protocol <stream-protocol>`.
     """
     _input_buf = ''
+
+    #: If not ``None``, :py:class:`Router` stamps this into
+    #: :py:attr:`Message.auth_id` of every message received on this stream.
     auth_id = None
 
     def __init__(self, router, remote_id, **kwargs):
@@ -993,6 +996,8 @@ class Router(object):
             if stream != expected_stream:
                 LOG.error('%r: bad source: got auth ID %r from %r, should be from %r',
                           self, msg, stream, expected_stream)
+            if stream.auth_id is not None:
+                msg.auth_id = stream.auth_id
 
         if msg.dst_id == mitogen.context_id:
             return self._invoke(msg)
diff --git a/mitogen/unix.py b/mitogen/unix.py
new file mode 100644
index 00000000..87abfaac
--- /dev/null
+++ b/mitogen/unix.py
@@ -0,0 +1,108 @@
+# Copyright 2017, David Wilson
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# 1. Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# 2. Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# 3. Neither the name of the copyright holder nor the names of its contributors
+# may be used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""
+Permit connection of additional contexts that may act with the authority of
+this context.
+"""
+
+import errno
+import os
+import socket
+import struct
+import tempfile
+
+import mitogen.core
+import mitogen.master
+
+from mitogen.core import LOG
+
+
+def is_path_dead(path):
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    try:
+        s.connect(path)
+    except socket.error, e:
+        if e[0] in (errno.ECONNREFUSED, errno.ENOENT):
+            return True
+        return False
+
+
+class Listener(mitogen.core.BasicStream):
+    keep_alive = True
+    def __init__(self, router, path=None, backlog=30):
+        self._router = router
+        self.path = path or tempfile.mktemp(prefix='mitogen_unix_')
+        self._sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+
+        if os.path.exists(self.path) and is_path_dead(self.path):
+            LOG.debug('%r: deleting stale %r', self, self.path)
+            os.unlink(self.path)
+
+        self._sock.bind(self.path)
+        os.chmod(self.path, 0600)
+        self._sock.listen(backlog)
+        mitogen.core.set_nonblock(self._sock.fileno())
+        mitogen.core.set_cloexec(self._sock.fileno())
+        self.path = self._sock.getsockname()
+        self.receive_side = mitogen.core.Side(self, self._sock.fileno())
+        router.broker.start_receive(self)
+
+    def on_receive(self, broker):
+        sock, _ = self._sock.accept()
+        context_id = self._router.id_allocator.allocate()
+        context = mitogen.master.Context(self._router, context_id)
+        stream = mitogen.core.Stream(self._router, context_id)
+        stream.accept(sock.fileno(), sock.fileno())
+        self._router.register(context, stream)
+        sock.send(struct.pack('>LL', context_id, mitogen.context_id))
+        sock.close()
+
+
+def connect(path):
+    LOG.debug('unix.connect(path=%r)', path)
+    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    sock.connect(path)
+    mitogen.context_id, remote_id = struct.unpack('>LL', sock.recv(8))
+    mitogen.parent_id = remote_id
+    mitogen.parent_ids = [remote_id]
+
+    LOG.debug('unix.connect(): local ID is %r, remote is %r',
+              mitogen.context_id, remote_id)
+
+    router = mitogen.master.Router()
+    stream = mitogen.core.Stream(router, remote_id)
+    stream.accept(sock.fileno(), sock.fileno())
+
+    context = mitogen.master.Context(router, remote_id)
+    router.register(context, stream)
+
+    mitogen.core.listen(router.broker, 'shutdown',
+        lambda: router.disconnect_stream(stream))
+
+    sock.close()
+    return router, context