| ''' |
| Copyright 2019 Google LLC |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| https://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| ''' |
| |
| |
| from typing import cast |
| from zeroconf import ServiceBrowser, Zeroconf |
| |
| import socket |
| import time |
| |
| |
| class DeviceNotFoundError(Exception): |
| pass |
| |
| |
| class Discoverer: |
| ANNOUNCE_PERIOD_SECS = 1 |
| MAXIMUM_WAIT_CYCLES = 10 |
| SERVICE_TYPE = "_googlemdt._tcp.local." |
| |
| def __init__(self, listener=None): |
| self.discoveries = {} |
| self.listener = listener |
| self.zeroconf = None |
| |
| def discover(self): |
| self.zeroconf = Zeroconf() |
| self.browser = ServiceBrowser(self.zeroconf, Discoverer.SERVICE_TYPE, self) |
| self._heard_announcement = True |
| cycle_count = 0 |
| |
| # Keep waiting until we stop hearing announcements for a full second, or until we've waited 10 seconds |
| while self._heard_announcement and cycle_count < Discoverer.MAXIMUM_WAIT_CYCLES: |
| cycle_count += 1 |
| self._heard_announcement = False |
| time.sleep(Discoverer.ANNOUNCE_PERIOD_SECS) |
| |
| self.browser.cancel() |
| self.browser = None |
| self.zeroconf = None |
| |
| def add_service(self, zeroconf, type, name): |
| info = self.zeroconf.get_service_info(type, name) |
| |
| if info: |
| hostname = info.server.split('.')[0] |
| address = info.parsed_addresses()[0] |
| |
| # Prevent duplicate announcements from extending the discovery delay |
| if hostname not in self.discoveries: |
| self._heard_announcement = True |
| |
| self.discoveries[hostname] = address |
| |
| if self.listener and hasattr(self.listener, "add_device"): |
| self.listener.add_device(hostname, address) |
| |
| def remove_service(self, zeroconf, type, name): |
| info = self.zeroconf.get_service_info(type, name) |
| |
| if info: |
| if self.listener and hasattr(self.listener, "remove_device"): |
| self.listener.remove_device(info.server, |
| self.discoveries[info.server]) |
| |
| if info.server in self.discoveries: |
| self._heard_announcement = True |
| del(self.discoveries[info.server]) |
| |
| def update_service(self, zeroconf, type, name): |
| """TODO(jtgans): Add this method once zeroconf figures out what it's for.""" |
| pass |
