Backport async API from master

.travis.yml

@@ -1,9 +1,10 @@
 language: python
 python:
-    - 3.6
-    - 3.5
-    - 2.7
-sudo: false
+    - "nightly"
+    - "3.8-dev"
+    - "3.7"
+    - "3.6"
+    - "3.5"
 install:
   - pip install --upgrade setuptools pip
   - pip install --upgrade --upgrade-strategy eager --pre -e .[test] pytest-cov pytest-warnings codecov

jupyter_client/__init__.py

@@ -6,4 +6,5 @@
 from .client import KernelClient
 from .manager import KernelManager, run_kernel
 from .blocking import BlockingKernelClient
+from .asynchronous import AsyncKernelClient
 from .multikernelmanager import MultiKernelManager

jupyter_client/asynchronous/__init__.py

@@ -0,0 +1 @@
+from .client import AsyncKernelClient

jupyter_client/asynchronous/channels.py

@@ -0,0 +1,82 @@
+"""Async channels"""
+
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+from queue import Queue, Empty
+
+
+class ZMQSocketChannel(object):
+    """A ZMQ socket in an async API"""
+    session = None
+    socket = None
+    stream = None
+    _exiting = False
+    proxy_methods = []
+
+    def __init__(self, socket, session, loop=None):
+        """Create a channel.
+
+        Parameters
+        ----------
+        socket : :class:`zmq.asyncio.Socket`
+            The ZMQ socket to use.
+        session : :class:`session.Session`
+            The session to use.
+        loop
+            Unused here, for other implementations
+        """
+        super(ZMQSocketChannel, self).__init__()
+
+        self.socket = socket
+        self.session = session
+
+    async def _recv(self, **kwargs):
+        msg = await self.socket.recv_multipart(**kwargs)
+        ident,smsg = self.session.feed_identities(msg)
+        return self.session.deserialize(smsg)
+
+    async def get_msg(self, timeout=None):
+        """ Gets a message if there is one that is ready. """
+        if timeout is not None:
+            timeout *= 1000  # seconds to ms
+        ready = await self.socket.poll(timeout)
+
+        if ready:
+            return await self._recv()
+        else:
+            raise Empty
+
+    async def get_msgs(self):
+        """ Get all messages that are currently ready. """
+        msgs = []
+        while True:
+            try:
+                msgs.append(await self.get_msg())
+            except Empty:
+                break
+        return msgs
+
+    async def msg_ready(self):
+        """ Is there a message that has been received? """
+        return bool(await self.socket.poll(timeout=0))
+
+    def close(self):
+        if self.socket is not None:
+            try:
+                self.socket.close(linger=0)
+            except Exception:
+                pass
+            self.socket = None
+    stop =  close
+
+    def is_alive(self):
+        return (self.socket is not None)
+
+    def send(self, msg):
+        """Pass a message to the ZMQ socket to send
+        """
+        self.session.send(self.socket, msg)
+
+    def start(self):
+        pass