diff --git a/sylk/applications/webrtcgateway/datatypes.py b/sylk/applications/webrtcgateway/datatypes.py
index f3e1e32..f4121d9 100644
--- a/sylk/applications/webrtcgateway/datatypes.py
+++ b/sylk/applications/webrtcgateway/datatypes.py
@@ -1,113 +1,120 @@
 import base64
 import hashlib
 import json
 import os
+from datetime import datetime, timedelta
 import urllib.parse
 
 from sipsimple.util import ISOTimestamp
 from sipsimple.configuration.settings import SIPSimpleSettings
 
 from sipsimple.streams.msrp.chat import CPIMPayload, ChatIdentity, CPIMHeader, CPIMNamespace
 from sylk.web import server
 from sylk.configuration.datatypes import URL
 
+from .configuration import GeneralConfig
 from .models import sylkrtc
 
 
 class FileTransferData(object):
-    def __init__(self, filename, filesize, filetype, transfer_id, sender, receiver, content=None):
+    def __init__(self, filename, filesize, filetype, transfer_id, sender, receiver, content=None, url=None):
         self.content = content
         self.filename = filename
         self.filesize = filesize
         self.filetype = filetype
         self.transfer_id = transfer_id
         self.sender = sylkrtc.SIPIdentity(uri=sender, display_name='')
         self.receiver = sylkrtc.SIPIdentity(uri=receiver, display_name='')
         self.hashed_sender = sender
         self.hashed_receiver = receiver
         self.prefix = self.hashed_sender[:1]
         self.path = self._get_initial_path()
         self.timestamp = str(ISOTimestamp.now())
-        self.url = self._set_url()
+        self.until = self._set_until()
+        self.url = self._set_url() if not url else url
 
     def _encode_and_hash_uri(self, uri):
         return base64.urlsafe_b64encode(hashlib.md5(uri.encode('utf-8')).digest()).rstrip(b'=\n').decode('utf-8')
 
     def _get_initial_path(self):
         settings = SIPSimpleSettings()
         return os.path.join(settings.file_transfer.directory.normalized, self.prefix, self.hashed_sender, self.hashed_receiver, self.transfer_id)
 
     def update_path_for_receiver(self):
         settings = SIPSimpleSettings()
         self.prefix = self.hashed_receiver[:1]
         self.path = os.path.join(settings.file_transfer.directory.normalized, self.prefix, self.hashed_receiver, self.hashed_sender, self.transfer_id)
         self.url = self._set_url()
 
+    def _set_until(self):
+        remove_after_days = GeneralConfig.filetransfer_expire_days
+        return str(ISOTimestamp(datetime.now() + timedelta(days=remove_after_days)))
+
     def _set_url(self):
         settings = SIPSimpleSettings()
         stripped_path = os.path.relpath(self.path, f'{settings.file_transfer.directory.normalized}/{self.prefix}')
         file_path = urllib.parse.quote(f'webrtcgateway/filetransfer/{stripped_path}/{self.filename}')
         return str(URL(f'{server.url}/{file_path}'))
 
     @property
     def full_path(self):
         return os.path.join(self.path, self.filename)
 
     @property
     def hashed_sender(self):
         return self._hashed_sender
 
     @hashed_sender.setter
     def hashed_sender(self, value):
         self._hashed_sender = self._encode_and_hash_uri(value)
 
     @property
     def hashed_receiver(self):
         return self._hashed_receiver
 
     @hashed_receiver.setter
     def hashed_receiver(self, value):
         self._hashed_receiver = self._encode_and_hash_uri(value)
 
     @property
     def message_payload(self):
         return f'File transfer available at {self.url} ({self.formatted_file_size})'
 
     def cpim_message_payload(self, metadata):
         return self.build_cpim_payload(self.sender.uri,
                                        self.receiver.uri,
                                        self.transfer_id,
                                        json.dumps(sylkrtc.FileTransferMessage(**metadata.__data__).__data__),
                                        content_type='application/sylk-file-transfer')
 
     @property
     def formatted_file_size(self):
         return self.format_file_size(self.filesize)
 
     @staticmethod
     def build_cpim_payload(account, uri, message_id, content, content_type='text/plain'):
         ns = CPIMNamespace('urn:ietf:params:imdn', 'imdn')
         additional_headers = [CPIMHeader('Message-ID', ns, message_id)]
         additional_headers.append(CPIMHeader('Disposition-Notification', ns, 'positive-delivery, display'))
         payload = CPIMPayload(content,
                               content_type,
                               charset='utf-8',
                               sender=ChatIdentity(account, None),
                               recipients=[ChatIdentity(uri, None)],
                               timestamp=str(ISOTimestamp.now()),
                               additional_headers=additional_headers)
         payload, content_type = payload.encode()
         return payload
 
     @staticmethod
     def format_file_size(size):
         infinite = float('infinity')
         boundaries = [(             1024, '%d bytes',               1),
                       (          10*1024, '%.2f KB',           1024.0),  (     1024*1024, '%.1f KB',           1024.0),
                       (     10*1024*1024, '%.2f MB',      1024*1024.0),  (1024*1024*1024, '%.1f MB',      1024*1024.0),
                       (10*1024*1024*1024, '%.2f GB', 1024*1024*1024.0),  (      infinite, '%.1f GB', 1024*1024*1024.0)]
         for boundary, format, divisor in boundaries:
             if size < boundary:
                 return format % (size/divisor,)
         else:
             return "%d bytes" % size
diff --git a/sylk/applications/webrtcgateway/models/sylkrtc.py b/sylk/applications/webrtcgateway/models/sylkrtc.py
index 9306b93..8962d29 100644
--- a/sylk/applications/webrtcgateway/models/sylkrtc.py
+++ b/sylk/applications/webrtcgateway/models/sylkrtc.py
@@ -1,648 +1,650 @@
 
 from application.python import subclasses
 
 from .jsonobjects import BooleanProperty, IntegerProperty, StringProperty, ArrayProperty, ObjectProperty, FixedValueProperty, LimitedChoiceProperty, AbstractObjectProperty, AbstractProperty
 from .jsonobjects import JSONObject, JSONArray, StringArray, CompositeValidator
 from .validators import AORValidator, DisplayNameValidator, LengthValidator, UniqueItemsValidator
 
 from sipsimple.util import ISOTimestamp
 
 # Base models (these are abstract and should not be used directly)
 
 class SylkRTCRequestBase(JSONObject):
     transaction = StringProperty()
 
 
 class SylkRTCResponseBase(JSONObject):
     transaction = StringProperty()
 
 
 class AccountRequestBase(SylkRTCRequestBase):
     account = StringProperty(validator=AORValidator())
 
 
 class SessionRequestBase(SylkRTCRequestBase):
     session = StringProperty()
 
 
 class VideoroomRequestBase(SylkRTCRequestBase):
     session = StringProperty()
 
 
 class AccountEventBase(JSONObject):
     sylkrtc = FixedValueProperty('account-event')
     account = StringProperty(validator=AORValidator())
 
 
 class SessionEventBase(JSONObject):
     sylkrtc = FixedValueProperty('session-event')
     session = StringProperty()
 
 
 class VideoroomEventBase(JSONObject):
     sylkrtc = FixedValueProperty('videoroom-event')
     session = StringProperty()
 
 
 class AccountRegistrationStateEvent(AccountEventBase):
     event = FixedValueProperty('registration-state')
 
 
 class SessionStateEvent(SessionEventBase):
     event = FixedValueProperty('state')
 
 
 class VideoroomSessionStateEvent(VideoroomEventBase):
     event = FixedValueProperty('session-state')
 
 
 # Miscellaneous models
 
 class Header(JSONObject):
     name = StringProperty()
     value = StringProperty()
 
 
 class Headers(JSONArray):
     item_type = Header
 
 
 class SIPIdentity(JSONObject):
     uri = StringProperty(validator=AORValidator())
     display_name = StringProperty(optional=True, validator=DisplayNameValidator())
 
 
 class ICECandidate(JSONObject):
     candidate = StringProperty()
     sdpMLineIndex = IntegerProperty()
     sdpMid = StringProperty()
 
 
 class ICECandidates(JSONArray):
     item_type = ICECandidate
 
 
 class AORList(StringArray):
     list_validator = UniqueItemsValidator()
     item_validator = AORValidator()
 
 
 class VideoroomPublisher(JSONObject):
     id = StringProperty()
     uri = StringProperty(validator=AORValidator())
     display_name = StringProperty(optional=True)
 
 
 class VideoroomPublishers(JSONArray):
     item_type = VideoroomPublisher
 
 
 class VideoroomActiveParticipants(StringArray):
     list_validator = CompositeValidator(UniqueItemsValidator(), LengthValidator(maximum=2))
 
 
 class VideoroomSessionOptions(JSONObject):
     audio = BooleanProperty(optional=True)
     video = BooleanProperty(optional=True)
     bitrate = IntegerProperty(optional=True)
 
 
 class VideoroomRaisedHands(StringArray):
     list_validator = UniqueItemsValidator()
 
 
 class SharedFile(JSONObject):
     filename = StringProperty()
     filesize = IntegerProperty()
     uploader = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     session = StringProperty()
 
 
 class SharedFiles(JSONArray):
     item_type = SharedFile
 
 
 class TransferredFile(JSONObject):
     filename = StringProperty()
     filesize = IntegerProperty()
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     receiver = ObjectProperty(SIPIdentity)
     transfer_id = StringProperty()
     prefix = StringProperty()
     path = StringProperty()
     timestamp = StringProperty()
+    until = StringProperty(optional=True)
     url = StringProperty(optional=True)
     filetype = StringProperty(optional=True)
     hash = StringProperty(optional=True)
 
 
 class FileTransferMessage(JSONObject):
     filename = StringProperty()
     filesize = IntegerProperty()
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     receiver = ObjectProperty(SIPIdentity)
     transfer_id = StringProperty()
     timestamp = StringProperty()
+    until = StringProperty(optional=True)
     url = StringProperty(optional=True)
     filetype = StringProperty(optional=True)
     hash = StringProperty(optional=True)
 
 
 class DispositionNotifications(StringArray):
     list_validator = UniqueItemsValidator()
 
 
 class Message(JSONObject):
     contact = StringProperty(validator=AORValidator())
     timestamp = StringProperty()
     disposition = ArrayProperty(DispositionNotifications, optional=True)
     message_id = StringProperty()
     content_type = StringProperty()
     content = StringProperty()
     direction = StringProperty(optional=True)
     state = LimitedChoiceProperty(['delivered', 'failed', 'displayed', 'forbidden', 'error', 'accepted', 'pending', 'received'], optional=True)
 
     def __init__(self, **kw):
         if 'msg_timestamp' in kw:
             kw['timestamp'] = str(ISOTimestamp(kw['msg_timestamp']))
             del kw['msg_timestamp']
         super(Message, self).__init__(**kw)
 
 
 class ContactMessages(JSONArray):
     item_type = Message
 
 
 class MessageHistoryData(JSONObject):
     account = StringProperty(validator=AORValidator())
     messages = ArrayProperty(ContactMessages)
 
 
 class AccountMessageRemoveEventData(JSONObject):
     contact = StringProperty()
     message_id = StringProperty()
 
 
 class AccountMarkConversationReadEventData(JSONObject):
     contact = StringProperty()
 
 
 class AccountConversationRemoveEventData(JSONObject):
     contact = StringProperty()
 
 
 class AccountDispositionNotificationEventData(JSONObject):
     message_id = StringProperty()
     state = LimitedChoiceProperty(['accepted', 'delivered', 'displayed', 'failed', 'processed', 'stored', 'forbidden', 'error'])
     message_timstamp = StringProperty()
     code = IntegerProperty()
     reason = StringProperty()
 
 
 class IncomingHeaderPrefixes(StringArray):
     list_validator = UniqueItemsValidator()
 
 
 # Response models
 
 class AckResponse(SylkRTCResponseBase):
     sylkrtc = FixedValueProperty('ack')
 
 
 class ErrorResponse(SylkRTCResponseBase):
     sylkrtc = FixedValueProperty('error')
     error = StringProperty()
 
 
 # Connection events
 
 class ReadyEvent(JSONObject):
     sylkrtc = FixedValueProperty('ready-event')
 
 
 class LookupPublicKeyEvent(JSONObject):
     sylkrtc = FixedValueProperty('lookup-public-key-event')
     uri = StringProperty(validator=AORValidator())
     public_key = StringProperty(optional=True)
 
 
 # Account events
 
 class AccountIncomingSessionEvent(AccountEventBase):
     event = FixedValueProperty('incoming-session')
     session = StringProperty()
     originator = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     sdp = StringProperty()
     call_id = StringProperty()
     headers = AbstractProperty(optional=True)
 
 
 class AccountMissedSessionEvent(AccountEventBase):
     event = FixedValueProperty('missed-session')
     originator = ObjectProperty(SIPIdentity)  # type: SIPIdentity
 
 
 class AccountConferenceInviteEvent(AccountEventBase):
     event = FixedValueProperty('conference-invite')
     room = StringProperty(validator=AORValidator())
     session_id = StringProperty()
     originator = ObjectProperty(SIPIdentity)  # type: SIPIdentity
 
 
 class AccountMessageEvent(AccountEventBase):
     event = FixedValueProperty('message')
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     timestamp = StringProperty()
     disposition_notification = ArrayProperty(DispositionNotifications, optional=True)
     message_id = StringProperty()
     content_type = StringProperty()
     content = StringProperty()
     direction = StringProperty(optional=True)
 
 
 class AccountDispositionNotificationEvent(AccountEventBase):
     event = FixedValueProperty('disposition-notification')
     message_id = StringProperty()
     message_timestamp = StringProperty()
     state = LimitedChoiceProperty(['accepted', 'delivered', 'displayed', 'failed', 'processed', 'stored', 'forbidden', 'error'])
     code = IntegerProperty()
     reason = StringProperty()
 
 
 class AccountSyncConversationsEvent(AccountEventBase):
     event = FixedValueProperty('sync-conversations')
     messages = ArrayProperty(ContactMessages)
 
 
 class AccountSyncEvent(AccountEventBase):
     event = FixedValueProperty('sync')
     type = StringProperty()
     action = StringProperty()
     content = AbstractObjectProperty()
 
 
 class AccountRegisteringEvent(AccountRegistrationStateEvent):
     state = FixedValueProperty('registering')
 
 
 class AccountRegisteredEvent(AccountRegistrationStateEvent):
     state = FixedValueProperty('registered')
 
 
 class AccountRegistrationFailedEvent(AccountRegistrationStateEvent):
     state = FixedValueProperty('failed')
     reason = StringProperty(optional=True)
 
 
 # Session events
 
 class SessionProgressEvent(SessionStateEvent):
     state = FixedValueProperty('progress')
 
 
 class SessionEarlyMediaEvent(SessionStateEvent):
     state = FixedValueProperty('early-media')
     sdp = StringProperty(optional=True)
     call_id = StringProperty(optional=True)
 
 
 class SessionAcceptedEvent(SessionStateEvent):
     state = FixedValueProperty('accepted')
     sdp = StringProperty(optional=True)  # missing for incoming sessions
     call_id = StringProperty(optional=True)
     headers = AbstractProperty(optional=True)
 
 
 class SessionEstablishedEvent(SessionStateEvent):
     state = FixedValueProperty('established')
 
 
 class SessionTerminatedEvent(SessionStateEvent):
     state = FixedValueProperty('terminated')
     reason = StringProperty(optional=True)
 
 
 class SessionMessageEvent(SessionEventBase):
     event = FixedValueProperty('message')
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     timestamp = StringProperty()
     disposition_notification = ArrayProperty(DispositionNotifications, optional=True)
     message_id = StringProperty()
     content_type = StringProperty()
     content = StringProperty()
     direction = StringProperty(optional=True)
 
 
 class SessionMessageDispositionNotificationEvent(SessionEventBase):
     event = FixedValueProperty('disposition-notification')
     message_id = StringProperty()
     message_timestamp = StringProperty()
     state = LimitedChoiceProperty(['accepted', 'delivered', 'displayed', 'failed', 'processed', 'stored', 'forbidden', 'error'])
     code = IntegerProperty()
     reason = StringProperty()
 
 
 # Video room events
 
 class VideoroomConfigureEvent(VideoroomEventBase):
     event = FixedValueProperty('configure')
     originator = StringProperty()
     active_participants = ArrayProperty(VideoroomActiveParticipants)  # type: VideoroomActiveParticipants
 
 
 class VideoroomSessionProgressEvent(VideoroomSessionStateEvent):
     state = FixedValueProperty('progress')
 
 
 class VideoroomSessionAcceptedEvent(VideoroomSessionStateEvent):
     state = FixedValueProperty('accepted')
     sdp = StringProperty()
     video = BooleanProperty(optional=True, default=True)
     audio = BooleanProperty(optional=True, default=True)
 
 
 class VideoroomSessionEstablishedEvent(VideoroomSessionStateEvent):
     state = FixedValueProperty('established')
 
 
 class VideoroomSessionTerminatedEvent(VideoroomSessionStateEvent):
     state = FixedValueProperty('terminated')
     reason = StringProperty(optional=True)
 
 
 class VideoroomFeedAttachedEvent(VideoroomEventBase):
     event = FixedValueProperty('feed-attached')
     feed = StringProperty()
     sdp = StringProperty()
 
 
 class VideoroomFeedEstablishedEvent(VideoroomEventBase):
     event = FixedValueProperty('feed-established')
     feed = StringProperty()
 
 
 class VideoroomInitialPublishersEvent(VideoroomEventBase):
     event = FixedValueProperty('initial-publishers')
     publishers = ArrayProperty(VideoroomPublishers)  # type: VideoroomPublishers
 
 
 class VideoroomPublishersJoinedEvent(VideoroomEventBase):
     event = FixedValueProperty('publishers-joined')
     publishers = ArrayProperty(VideoroomPublishers)  # type: VideoroomPublishers
 
 
 class VideoroomPublishersLeftEvent(VideoroomEventBase):
     event = FixedValueProperty('publishers-left')
     publishers = ArrayProperty(StringArray)          # type: StringArray
 
 
 class VideoroomFileSharingEvent(VideoroomEventBase):
     event = FixedValueProperty('file-sharing')
     files = ArrayProperty(SharedFiles)               # type: SharedFiles
 
 
 class VideoroomMessageEvent(VideoroomEventBase):
     event = FixedValueProperty('message')
     type = LimitedChoiceProperty(['normal', 'status'])
     content = StringProperty()
     content_type = StringProperty()
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
     timestamp = StringProperty()
 
 
 class VideoroomComposingIndicationEvent(VideoroomEventBase):
     event = FixedValueProperty('composing-indication')
     state = StringProperty()
     refresh = IntegerProperty()
     content_type = StringProperty()
     sender = ObjectProperty(SIPIdentity)  # type: SIPIdentity
 
 
 class VideoroomMessageDeliveryEvent(VideoroomEventBase):
     event = FixedValueProperty('message-delivery')
     message_id = StringProperty()
     delivered = BooleanProperty()
     code = IntegerProperty()
     reason = StringProperty()
 
 
 class VideoroomMuteAudioEvent(VideoroomEventBase):
     event = FixedValueProperty('mute-audio')
     originator = StringProperty()
 
 
 class VideoroomRaisedHandsEvent(VideoroomEventBase):
     event = FixedValueProperty('raised-hands')
     raised_hands = ArrayProperty(VideoroomRaisedHands)
 
 
 # Ping request model, can be used to check connectivity from client
 
 class PingRequest(SylkRTCRequestBase):
     sylkrtc = FixedValueProperty('ping')
 
 
 # Lookup Public key model
 
 class LookupPublicKeyRequest(SylkRTCRequestBase):
     sylkrtc = FixedValueProperty('lookup-public-key')
     uri = StringProperty(validator=AORValidator())
 
 
 # Account request models
 
 class AccountAddRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-add')
     password = StringProperty(validator=LengthValidator(minimum=1, maximum=9999))
     display_name = StringProperty(optional=True)
     user_agent = StringProperty(optional=True)
     incoming_header_prefixes = ArrayProperty(IncomingHeaderPrefixes, optional=True)
 
 
 class AccountRemoveRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-remove')
 
 
 class AccountRegisterRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-register')
 
 
 class AccountUnregisterRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-unregister')
 
 
 class AccountDeviceTokenRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-devicetoken')
     token = StringProperty()
     platform = StringProperty()
     device = StringProperty()
     silent = BooleanProperty(default=False)
     app = StringProperty()
 
 
 class AccountMessageRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-message')
     uri = StringProperty(validator=AORValidator())
     message_id = StringProperty()
     content = StringProperty()
     content_type = StringProperty()
     timestamp = StringProperty()
     server_generated = BooleanProperty(optional=True)
 
 
 class AccountDispositionNotificationRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-disposition-notification')
     uri = StringProperty(validator=AORValidator())
     message_id = StringProperty()
     state = LimitedChoiceProperty(['delivered', 'failed', 'displayed', 'forbidden', 'error'])
     timestamp = StringProperty()
 
 
 class AccountSyncConversationsRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-sync-conversations')
     message_id = StringProperty(optional=True)
 
 
 class AccountMarkConversationReadRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-mark-conversation-read')
     contact = StringProperty(validator=AORValidator())
 
 
 class AccountMessageRemoveRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-remove-message')
     message_id = StringProperty()
     contact = StringProperty(validator=AORValidator())
 
 
 class AccountConversationRemoveRequest(AccountRequestBase):
     sylkrtc = FixedValueProperty('account-remove-conversation')
     contact = StringProperty(validator=AORValidator())
 
 
 # Session request models
 
 class SessionCreateRequest(SessionRequestBase):
     sylkrtc = FixedValueProperty('session-create')
     account = StringProperty(validator=AORValidator())
     uri = StringProperty(validator=AORValidator())
     sdp = StringProperty()
     headers = ArrayProperty(Headers, optional=True)
 
 
 class SessionAnswerRequest(SessionRequestBase):
     sylkrtc = FixedValueProperty('session-answer')
     sdp = StringProperty()
     headers = ArrayProperty(Headers, optional=True)
 
 
 class SessionTrickleRequest(SessionRequestBase):
     sylkrtc = FixedValueProperty('session-trickle')
     candidates = ArrayProperty(ICECandidates)  # type: ICECandidates
 
 
 class SessionTerminateRequest(SessionRequestBase):
     sylkrtc = FixedValueProperty('session-terminate')
 
 
 class SessionMessageRequest(SessionRequestBase):
     sylkrtc = FixedValueProperty('session-message')
     message_id = StringProperty()
     content = StringProperty()
     content_type = StringProperty()
     timestamp = StringProperty()
 
 
 # Videoroom request models
 
 class VideoroomJoinRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-join')
     account = StringProperty(validator=AORValidator())
     uri = StringProperty(validator=AORValidator())
     sdp = StringProperty()
     audio = BooleanProperty(optional=True, default=True)
     video = BooleanProperty(optional=True, default=True)
 
 
 class VideoroomLeaveRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-leave')
 
 
 class VideoroomConfigureRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-configure')
     active_participants = ArrayProperty(VideoroomActiveParticipants)  # type: VideoroomActiveParticipants
 
 
 class VideoroomFeedAttachRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-feed-attach')
     publisher = StringProperty()
     feed = StringProperty()
 
 
 class VideoroomFeedAnswerRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-feed-answer')
     feed = StringProperty()
     sdp = StringProperty()
 
 
 class VideoroomFeedDetachRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-feed-detach')
     feed = StringProperty()
 
 
 class VideoroomInviteRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-invite')
     participants = ArrayProperty(AORList)              # type: AORList
 
 
 class VideoroomSessionTrickleRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-session-trickle')
     candidates = ArrayProperty(ICECandidates)          # type: ICECandidates
 
 
 class VideoroomSessionUpdateRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-session-update')
     options = ObjectProperty(VideoroomSessionOptions)  # type: VideoroomSessionOptions
 
 
 class VideoroomMessageRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-message')
     message_id = StringProperty()
     content = StringProperty()
     content_type = StringProperty()
 
 
 class VideoroomComposingIndicationRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-composing-indication')
     state = LimitedChoiceProperty(['active', 'idle'])
     refresh = IntegerProperty(optional=True)
 
 
 class VideoroomMuteAudioParticipantsRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-mute-audio-participants')
 
 
 class VideoroomToggleHandRequest(VideoroomRequestBase):
     sylkrtc = FixedValueProperty('videoroom-toggle-hand')
     session_id = StringProperty(optional=True)
 
 
 # SylkRTC request to model mapping
 
 class ProtocolError(Exception):
     pass
 
 
 class SylkRTCRequest(object):
     __classmap__ = {cls.sylkrtc.value: cls for cls in subclasses(SylkRTCRequestBase) if hasattr(cls, 'sylkrtc')}
 
     @classmethod
     def from_message(cls, message):
         try:
             request_type = message['sylkrtc']
         except KeyError:
             raise ProtocolError('could not get WebSocket message type')
         try:
             request_class = cls.__classmap__[request_type]
         except KeyError:
             raise ProtocolError('unknown WebSocket request: %s' % request_type)
         return request_class(**message)