Python, WebRTC and You (v2)
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Slides from the talk I gave at PyGrunn 2015 about using Python (asyncio + aiohttp) as the backend for WebRTC applications.
![class StaticFilesHandler:
def __init__(self, base_path):
self.base_path = base_path
self.cache = {}
!
@asyncio.coroutine
def __call__(self, request):
path = request.match_info['path']
try:
data, content_type = self.cache[path]
except KeyError:
full_path = os.path.join(self.base_path, path)
try:
with open(full_path, 'rb') as f:
content_type, encoding = mimetypes.guess_type(full_path,
strict=False)
data = f.read()
except IOError:
log.warning('Could not open %s file' % path)
raise web.HTTPNotFound()
self.cache[path] = data, content_type
log.debug('Loaded file %s (%s)' % (path, content_type))
return web.Response(body=data, content_type=content_type)](https://image.slidesharecdn.com/hp1gpghmq6ok01dp9jpj-signature-9ba5db90811b49a72360d6f530af4f64a935957d34ef09c54c6869f60f27b2b1-poli-150522131700-lva1-app6891/85/Python-WebRTC-and-You-v2-41-320.jpg)
![class WebSocketHandler:
def __init__(self):
self.waiter = None
!
@asyncio.coroutine
def __call__(self, request):
ws = web.WebSocketResponse(protocols=('callroulette-v2',))
ws.start(request)
!
conn = Connection(ws)
if self.waiter is None:
self.waiter = asyncio.Future(loop=ws._loop)
fs = [conn.read(), self.waiter]
done, pending = yield from asyncio.wait(fs, return_when=asyncio.FIRST_COMPLETED)
if self.waiter not in done:
# the connection was most likely closed
self.waiter = None
return ws
other = self.waiter.result()
self.waiter = None
reading_task = pending.pop()
reading_task.cancel()
asyncio.async(self.run_roulette(conn, other))
else:
self.waiter.set_result(conn)
!
yield from conn.wait_closed()
!
return ws](https://image.slidesharecdn.com/hp1gpghmq6ok01dp9jpj-signature-9ba5db90811b49a72360d6f530af4f64a935957d34ef09c54c6869f60f27b2b1-poli-150522131700-lva1-app6891/85/Python-WebRTC-and-You-v2-42-320.jpg)
![from jsonmodels import models, fields
from jsonmodels.errors import ValidationError
!
!
class StringChoiceField(fields.StringField):
def __init__(self, choices=None, *args, **kw):
self.choices = choices or []
super(StringChoiceField, self).__init__(*args, **kw)
!
def validate(self, value):
if value not in self.choices:
raise ValidationError('invalid choice value')
super(StringChoiceField, self).validate(value)
!
class Jsep(models.Base):
type = StringChoiceField(choices=['offer', 'answer'], required=True)
sdp = fields.StringField(required=True)
!
class Candidate(models.Base):
candidate = fields.StringField(required=True)
sdpMid = fields.StringField(required=True)
sdpMLineIndex = fields.IntField(required=True)
!
class YoPayload(models.Base):
yo = fields.StringField(required=True)
jsep = fields.EmbeddedField(Jsep)
candidate = fields.EmbeddedField(Candidate)](https://image.slidesharecdn.com/hp1gpghmq6ok01dp9jpj-signature-9ba5db90811b49a72360d6f530af4f64a935957d34ef09c54c6869f60f27b2b1-poli-150522131700-lva1-app6891/85/Python-WebRTC-and-You-v2-43-320.jpg)
![@asyncio.coroutine
def run_roulette(self, peerA, peerB):
log.info('Running roulette: %s, %s' % (peerA, peerB))
!
@asyncio.coroutine
def close_connections():
yield from asyncio.wait([peerA.close(), peerB.close()],
return_when=asyncio.ALL_COMPLETED)
!
def parse(data):
try:
data = json.loads(data)
payload = YoPayload(**data)
payload.validate()
except Exception as e:
log.warning('Error parsing payload: %s' % e)
return None
return payload](https://image.slidesharecdn.com/hp1gpghmq6ok01dp9jpj-signature-9ba5db90811b49a72360d6f530af4f64a935957d34ef09c54c6869f60f27b2b1-poli-150522131700-lva1-app6891/85/Python-WebRTC-and-You-v2-44-320.jpg)
![# wait for candidates / end
while True:
peer_a_read = asyncio.async(peerA.read())
peer_a_read.other_peer = peerB
peer_b_read = asyncio.async(peerB.read())
peer_b_read.other_peer = peerA
done, pending = yield from asyncio.wait([peer_a_read, peer_b_read],
return_when=asyncio.FIRST_COMPLETED)
for task in pending:
task.cancel()
for task in done:
data = task.result()
if not data:
break
# all we can get at this point is trickled ICE candidates
candidate = parse(data)
if candidate is None or candidate.candidate is None:
log.warning('Invalid candidate received!')
break
task.other_peer.write(json.dumps(candidate.to_struct()))
else:
continue
break
# close connections
yield from close_connections()](https://image.slidesharecdn.com/hp1gpghmq6ok01dp9jpj-signature-9ba5db90811b49a72360d6f530af4f64a935957d34ef09c54c6869f60f27b2b1-poli-150522131700-lva1-app6891/85/Python-WebRTC-and-You-v2-47-320.jpg)
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Python, WebRTC and You (v2)
- 1. Python, WebRTC and You Saúl Ibarra Corretgé @saghul v2
- 4. Have you ever used it?
- 6. What is WebRTC? WebRTC (Web Real-Time Communication) is an API definition drafted by the World Wide Web Consortium (W3C) that supports browser-to-browser applications for voice calling, video chat, and P2P file sharing without the need of either internal or external plugins.
- 11. You need an adapter Implementation in browsers is currently inconsistent Some APIs are still in flux
- 13. Temasys WebRTC Plugin Free (as in beer) plugin for IE and Safari http://skylink.io/plugin/
- 15. getUserMedia if (!rtcninja.hasWebRTC()) { console.log('Are you from the past?!'); return; } ! rtcninja.getUserMedia( // constraints {video: true, audio: true}, ! // successCallback function(localMediaStream) { var video = document.querySelector('video'); rtcninja.attachMediaStream(video, localMediaStream); }, ! // errorCallback function(err) { console.log("The following error occured: " + err); } );
- 17. RTCPeerConnection Handles streaming of media between 2 peers Uses state of the art technology JSEP
- 18. RTCPeerConnection (2) Get local media Send SDP offer Get local media Send SDP answer ICE candidates Audio / Video
- 20. ICE Helps find the best path for media Solves NAT traversal and other hostile network problems Communication Consent Verification It can trickle!
- 22. What about the signalling? It’s not specified! Use SIP, XMPP or roll your own!
- 25. RTCDataChannel P2P, message boundary based channel for arbitrary data Implemented using SCTP, different reliability choices possible
- 27. Call Roulette
- 29. The Protocol WebSocket based, JSON payload Users enter the roulette when they connect over WebSocket Session is negotiated / established No end message, just disconnect the WebSocket
- 31. yo (v2)
- 32. {'yo': 'yo'}
- 33. {'jsep': {'sdp': '...', 'type': 'offer'}, 'yo': 'yo'}
- 34. {'jsep': {'sdp': '...', 'type': 'answer'}, 'yo': 'yo'}
- 35. {'candidate': {'candidate': '...', 'sdpMLineIndex': 1, 'sdpMid': ''}, 'yo': 'yo'}
- 37. Shopping for a framework Python >= 3.3, because future! WebSocket support built-in Async, because blocking is so 2001 New, because why not?
- 40. @asyncio.coroutine def init(loop): app = web.Application(loop=loop) app.router.add_route('GET', '/', LazyFileHandler(INDEX_FILE, 'text/html')) app.router.add_route('GET', '/ws', WebSocketHandler()) app.router.add_route('GET', '/static/{path:.*}', StaticFilesHandler(STATIC_FILES)) ! handler = app.make_handler() server = yield from loop.create_server(handler, '0.0.0.0', 8080) print("Server started at http://0.0.0.0:8080") return server, handler
- 41. class StaticFilesHandler: def __init__(self, base_path): self.base_path = base_path self.cache = {} ! @asyncio.coroutine def __call__(self, request): path = request.match_info['path'] try: data, content_type = self.cache[path] except KeyError: full_path = os.path.join(self.base_path, path) try: with open(full_path, 'rb') as f: content_type, encoding = mimetypes.guess_type(full_path, strict=False) data = f.read() except IOError: log.warning('Could not open %s file' % path) raise web.HTTPNotFound() self.cache[path] = data, content_type log.debug('Loaded file %s (%s)' % (path, content_type)) return web.Response(body=data, content_type=content_type)
- 42. class WebSocketHandler: def __init__(self): self.waiter = None ! @asyncio.coroutine def __call__(self, request): ws = web.WebSocketResponse(protocols=('callroulette-v2',)) ws.start(request) ! conn = Connection(ws) if self.waiter is None: self.waiter = asyncio.Future(loop=ws._loop) fs = [conn.read(), self.waiter] done, pending = yield from asyncio.wait(fs, return_when=asyncio.FIRST_COMPLETED) if self.waiter not in done: # the connection was most likely closed self.waiter = None return ws other = self.waiter.result() self.waiter = None reading_task = pending.pop() reading_task.cancel() asyncio.async(self.run_roulette(conn, other)) else: self.waiter.set_result(conn) ! yield from conn.wait_closed() ! return ws
- 43. from jsonmodels import models, fields from jsonmodels.errors import ValidationError ! ! class StringChoiceField(fields.StringField): def __init__(self, choices=None, *args, **kw): self.choices = choices or [] super(StringChoiceField, self).__init__(*args, **kw) ! def validate(self, value): if value not in self.choices: raise ValidationError('invalid choice value') super(StringChoiceField, self).validate(value) ! class Jsep(models.Base): type = StringChoiceField(choices=['offer', 'answer'], required=True) sdp = fields.StringField(required=True) ! class Candidate(models.Base): candidate = fields.StringField(required=True) sdpMid = fields.StringField(required=True) sdpMLineIndex = fields.IntField(required=True) ! class YoPayload(models.Base): yo = fields.StringField(required=True) jsep = fields.EmbeddedField(Jsep) candidate = fields.EmbeddedField(Candidate)
- 44. @asyncio.coroutine def run_roulette(self, peerA, peerB): log.info('Running roulette: %s, %s' % (peerA, peerB)) ! @asyncio.coroutine def close_connections(): yield from asyncio.wait([peerA.close(), peerB.close()], return_when=asyncio.ALL_COMPLETED) ! def parse(data): try: data = json.loads(data) payload = YoPayload(**data) payload.validate() except Exception as e: log.warning('Error parsing payload: %s' % e) return None return payload
- 45. # request offer offer_request = YoPayload(yo='yo') peerA.write(json.dumps(offer_request.to_struct())) ! # get offer data = yield from peerA.read(timeout=READ_TIMEOUT) if not data: yield from close_connections() return ! offer = parse(data) if offer is None or offer.jsep is None or offer.jsep.type != 'offer': log.warning('Invalid offer received') yield from close_connections() return ! # send offer peerB.write(json.dumps(offer.to_struct()))
- 46. # wait for answer data = yield from peerB.read(timeout=READ_TIMEOUT) if not data: yield from close_connections() return ! answer = parse(data) if answer is None or answer.jsep is None or answer.jsep.type != 'answer': log.warning('Invalid answer received') yield from close_connections() return ! # dispatch answer peerA.write(json.dumps(answer.to_struct()))
- 47. # wait for candidates / end while True: peer_a_read = asyncio.async(peerA.read()) peer_a_read.other_peer = peerB peer_b_read = asyncio.async(peerB.read()) peer_b_read.other_peer = peerA done, pending = yield from asyncio.wait([peer_a_read, peer_b_read], return_when=asyncio.FIRST_COMPLETED) for task in pending: task.cancel() for task in done: data = task.result() if not data: break # all we can get at this point is trickled ICE candidates candidate = parse(data) if candidate is None or candidate.candidate is None: log.warning('Invalid candidate received!') break task.other_peer.write(json.dumps(candidate.to_struct())) else: continue break # close connections yield from close_connections()