Python, WebRTC and You (v2)
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The document provides an overview of WebRTC (Web Real-Time Communication), detailing its APIs for browser-to-browser communication, including voice calls and video chats without plugins. It discusses key components like getUserMedia, RTCPeerConnection, and RTCDataChannel, as well as the need for signaling methods and the framework for implementing a call roulette application in Python using asyncio. Additionally, it covers the handling of WebSocket connections and the exchange of offer/answer messages for establishing peer connections.
![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)
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()