diff --git a/apiclient/channel.py b/apiclient/channel.py
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+++ b/apiclient/channel.py
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+"""Channel notifications support.
+
+Classes and functions to support channel subscriptions and notifications
+on those channels.
+
+Notes:
+  - This code is based on experimental APIs and is subject to change.
+  - Notification does not do deduplication of notification ids, that's up to
+    the receiver.
+  - Storing the Channel between calls is up to the caller.
+
+
+Example setting up a channel:
+
+  # Create a new channel that gets notifications via webhook.
+  channel = new_webhook_channel("https://example.com/my_web_hook")
+
+  # Store the channel, keyed by 'channel.id'. Store it before calling the
+  # watch method because notifications may start arriving before the watch
+  # method returns.
+  ...
+
+  resp = service.objects().watchAll(
+    bucket="some_bucket_id", body=channel.body()).execute()
+  channel.update(resp)
+
+  # Store the channel, keyed by 'channel.id'. Store it after being updated
+  # since the resource_id value will now be correct, and that's needed to
+  # stop a subscription.
+  ...
+
+
+An example Webhook implementation using webapp2. Note that webapp2 puts
+headers in a case insensitive dictionary, as headers aren't guaranteed to
+always be upper case.
+
+  id = self.request.headers[X_GOOG_CHANNEL_ID]
+
+  # Retrieve the channel by id.
+  channel = ...
+
+  # Parse notification from the headers, including validating the id.
+  n = notification_from_headers(channel, self.request.headers)
+
+  # Do app specific stuff with the notification here.
+  if n.resource_state == 'sync':
+    # Code to handle sync state.
+  elif n.resource_state == 'exists':
+    # Code to handle the exists state.
+  elif n.resource_state == 'not_exists':
+    # Code to handle the not exists state.
+
+
+Example of unsubscribing.
+
+  service.channels().stop(channel.body())
+"""
+
+import datetime
+import uuid
+
+from apiclient import errors
+from oauth2client import util
+
+
+# The unix time epoch starts at midnight 1970.
+EPOCH = datetime.datetime.utcfromtimestamp(0)
+
+# Map the names of the parameters in the JSON channel description to
+# the parameter names we use in the Channel class.
+CHANNEL_PARAMS = {
+    'address': 'address',
+    'id': 'id',
+    'expiration': 'expiration',
+    'params': 'params',
+    'resourceId': 'resource_id',
+    'resourceUri': 'resource_uri',
+    'type': 'type',
+    'token': 'token',
+    }
+
+X_GOOG_CHANNEL_ID     = 'X-GOOG-CHANNEL-ID'
+X_GOOG_MESSAGE_NUMBER = 'X-GOOG-MESSAGE-NUMBER'
+X_GOOG_RESOURCE_STATE = 'X-GOOG-RESOURCE-STATE'
+X_GOOG_RESOURCE_URI   = 'X-GOOG-RESOURCE-URI'
+X_GOOG_RESOURCE_ID    = 'X-GOOG-RESOURCE-ID'
+
+
+def _upper_header_keys(headers):
+  new_headers = {}
+  for k, v in headers.iteritems():
+    new_headers[k.upper()] = v
+  return new_headers
+
+
+class Notification(object):
+  """A Notification from a Channel.
+
+  Notifications are not usually constructed directly, but are returned
+  from functions like notification_from_headers().
+
+  Attributes:
+    message_number: int, The unique id number of this notification.
+    state: str, The state of the resource being monitored.
+    uri: str, The address of the resource being monitored.
+    resource_id: str, The unique identifier of the version of the resource at
+      this event.
+  """
+  @util.positional(5)
+  def __init__(self, message_number, state, resource_uri, resource_id):
+    """Notification constructor.
+
+    Args:
+      message_number: int, The unique id number of this notification.
+      state: str, The state of the resource being monitored. Can be one
+        of "exists", "not_exists", or "sync".
+      resource_uri: str, The address of the resource being monitored.
+      resource_id: str, The identifier of the watched resource.
+    """
+    self.message_number = message_number
+    self.state = state
+    self.resource_uri = resource_uri
+    self.resource_id = resource_id
+
+
+class Channel(object):
+  """A Channel for notifications.
+
+  Usually not constructed directly, instead it is returned from helper
+  functions like new_webhook_channel().
+
+  Attributes:
+    type: str, The type of delivery mechanism used by this channel. For
+      example, 'web_hook'.
+    id: str, A UUID for the channel.
+    token: str, An arbitrary string associated with the channel that
+      is delivered to the target address with each event delivered
+      over this channel.
+    address: str, The address of the receiving entity where events are
+      delivered. Specific to the channel type.
+    expiration: int, The time, in milliseconds from the epoch, when this
+      channel will expire.
+    params: dict, A dictionary of string to string, with additional parameters
+      controlling delivery channel behavior.
+    resource_id: str, An opaque id that identifies the resource that is
+      being watched. Stable across different API versions.
+    resource_uri: str, The canonicalized ID of the watched resource.
+  """
+
+  @util.positional(5)
+  def __init__(self, type, id, token, address, expiration=None,
+               params=None, resource_id="", resource_uri=""):
+    """Create a new Channel.
+
+    In user code, this Channel constructor will not typically be called
+    manually since there are functions for creating channels for each specific
+    type with a more customized set of arguments to pass.
+
+    Args:
+      type: str, The type of delivery mechanism used by this channel. For
+        example, 'web_hook'.
+      id: str, A UUID for the channel.
+      token: str, An arbitrary string associated with the channel that
+        is delivered to the target address with each event delivered
+        over this channel.
+      address: str,  The address of the receiving entity where events are
+        delivered. Specific to the channel type.
+      expiration: int, The time, in milliseconds from the epoch, when this
+        channel will expire.
+      params: dict, A dictionary of string to string, with additional parameters
+        controlling delivery channel behavior.
+      resource_id: str, An opaque id that identifies the resource that is
+        being watched. Stable across different API versions.
+      resource_uri: str, The canonicalized ID of the watched resource.
+    """
+    self.type = type
+    self.id = id
+    self.token = token
+    self.address = address
+    self.expiration = expiration
+    self.params = params
+    self.resource_id = resource_id
+    self.resource_uri = resource_uri
+
+  def body(self):
+    """Build a body from the Channel.
+
+    Constructs a dictionary that's appropriate for passing into watch()
+    methods as the value of body argument.
+
+    Returns:
+      A dictionary representation of the channel.
+    """
+    result = {
+        'id': self.id,
+        'token': self.token,
+        'type': self.type,
+        'address': self.address
+        }
+    if self.params:
+      result['params'] = self.params
+    if self.resource_id:
+      result['resourceId'] = self.resource_id
+    if self.resource_uri:
+      result['resourceUri'] = self.resource_uri
+    if self.expiration:
+      result['expiration'] = self.expiration
+
+    return result
+
+  def update(self, resp):
+    """Update a channel with information from the response of watch().
+
+    When a request is sent to watch() a resource, the response returned
+    from the watch() request is a dictionary with updated channel information,
+    such as the resource_id, which is needed when stopping a subscription.
+
+    Args:
+      resp: dict, The response from a watch() method.
+    """
+    for json_name, param_name in CHANNEL_PARAMS.iteritems():
+      value = resp.get(json_name)
+      if value is not None:
+        setattr(self, param_name, value)
+
+
+def notification_from_headers(channel, headers):
+  """Parse a notification from the webhook request headers, validate
+    the notification, and return a Notification object.
+
+  Args:
+    channel: Channel, The channel that the notification is associated with.
+    headers: dict, A dictionary like object that contains the request headers
+      from the webhook HTTP request.
+
+  Returns:
+    A Notification object.
+
+  Raises:
+    errors.InvalidNotificationError if the notification is invalid.
+    ValueError if the X-GOOG-MESSAGE-NUMBER can't be converted to an int.
+  """
+  headers = _upper_header_keys(headers)
+  channel_id = headers[X_GOOG_CHANNEL_ID]
+  if channel.id != channel_id:
+    raise errors.InvalidNotificationError(
+        'Channel id mismatch: %s != %s' % (channel.id, channel_id))
+  else:
+    message_number = int(headers[X_GOOG_MESSAGE_NUMBER])
+    state = headers[X_GOOG_RESOURCE_STATE]
+    resource_uri = headers[X_GOOG_RESOURCE_URI]
+    resource_id = headers[X_GOOG_RESOURCE_ID]
+    return Notification(message_number, state, resource_uri, resource_id)
+
+
+@util.positional(2)
+def new_webhook_channel(url, token=None, expiration=None, params=None):
+    """Create a new webhook Channel.
+
+    Args:
+      url: str, URL to post notifications to.
+      token: str, An arbitrary string associated with the channel that
+        is delivered to the target address with each notification delivered
+        over this channel.
+      expiration: datetime.datetime, A time in the future when the channel
+        should expire. Can also be None if the subscription should use the
+        default expiration. Note that different services may have different
+        limits on how long a subscription lasts. Check the response from the
+        watch() method to see the value the service has set for an expiration
+        time.
+      params: dict, Extra parameters to pass on channel creation. Currently
+        not used for webhook channels.
+    """
+    expiration_ms = 0
+    if expiration:
+      delta = expiration - EPOCH
+      expiration_ms = delta.microseconds/1000 + (
+          delta.seconds + delta.days*24*3600)*1000
+      if expiration_ms < 0:
+        expiration_ms = 0
+
+    return Channel('web_hook', str(uuid.uuid4()),
+                   token, url, expiration=expiration_ms,
+                   params=params)
+