4.1.2.2 Flow Sequence

Topic Version	1	Published	10/16/2017	Topic Change History
For Standard	ETPW14 v1

When the consumer/aggregator initiates the connection, the recommended sequence of activities to stream data using ETP is described in the table below.

	Producer (Sensor)/ETP Server	Consumer (Aggregator)/ETP Client
1	Provide an ETP WebSocket server at a known URL (see Preconditions above).
2		Protocol 0: Open WebSocket via HTTP call to WebSocket URL.
3		Send RequestSession message and role as a “consumer”.
4	Send OpenSession. Include ProtocolCapabilities of SimpleStreamer = true.
5		Protocol 1: Send Start message, which may contain throttling parameters.
6	Send ChannelMetadata message(s), which contains local identifiers for the channel(s).
7		Decode ChannelMetadata, assigning channels to a well/wellbore/log/logCurveInfo hierarchy. This decoding and assigning of channels must be completed before any channel data can be received.
8	Begin a sending loop, sending ChannelData messages for all channel data as they are available.
9		Decode each ChannelData message and append it to the appropriate WITSML log object and/or makes it available as ETP channel data to other consumers.
10		Protocol 0: To terminate data transfer, send CloseSession.

To terminate the session, the consumer typically sends the CloseSession message, but the producer can also send a CloseSession message if, for some reason, it had to stop sending data.