ping pong over websocket in ringserver

[crotwell]

Default python websockets send a PING periodically to keep a websocket connection alive. When this happens, ringserver appears to close the connection.

Would be nice if ringserver dali over websocket allowed PING-PONG.

Spec stuff here:
https://www.rfc-editor.org/rfc/rfc6455.html#section-5.5.2

If not, would be good if it could log the close with a reason in the server side logging. Currently I get a disconnet but no reason or even info that that a bad command was sent:

Tue Oct 26 15:42:56 2021 - Server thread (Listen) 6094106624 Flags: ACTIVE
Tue Oct 26 15:42:56 2021 - Server thread (Listen) 6094680064 Flags: ACTIVE
Tue Oct 26 15:42:56 2021 - Client thread 6095253504 Flags: ACTIVE
Tue Oct 26 15:42:56 2021 - Client connections: 1
Tue Oct 26 15:42:56 2021 - Client disconnected: localhost
Tue Oct 26 15:42:57 2021 - Server thread (Listen) 6094106624 Flags: ACTIVE
Tue Oct 26 15:42:57 2021 - Server thread (Listen) 6094680064 Flags: ACTIVE
Tue Oct 26 15:42:57 2021 - Client thread 6095253504 Flags: CLOSED
Tue Oct 26 15:42:57 2021 - Removing client thread 6095253504 from the cthreads list
Tue Oct 26 15:42:57 2021 - Client connections: 0

and on the python side I get a frame error, I think because the websocket doesn't go through a normal shutdown sequence.

Stream
DEBUG:websockets.client:%% sending keepalive ping
DEBUG:websockets.client:> PING 4e 49 9a 74 [binary, 4 bytes]
DEBUG:websockets.client:! failing connection with code 1002
DEBUG:websockets.client:= connection is CLOSING
DEBUG:websockets.client:> CLOSE 1002 (protocol error) [2 bytes]
DEBUG:websockets.client:= connection is CLOSED
Traceback (most recent call last):
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 944, in transfer_data
    message = await self.read_message()
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 1013, in read_message
    frame = await self.read_data_frame(max_size=self.max_size)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 1089, in read_data_frame
    frame = await self.read_frame(max_size)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 1144, in read_frame
    frame = await Frame.read(
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/framing.py", line 85, in read
    raise ProtocolError("incorrect masking")
websockets.exceptions.ProtocolError: incorrect masking

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/crotwell/dev/seis/simple-dali/example/readdali.py", line 91, in <module>
    asyncio.run(main(host, port, verbose=True), debug=debug)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
    return future.result()
  File "/Users/crotwell/dev/seis/simple-dali/example/readdali.py", line 84, in main
    await stream_data(dali)
  File "/Users/crotwell/dev/seis/simple-dali/example/readdali.py", line 24, in stream_data
    daliPacket = await dali.parseResponse()
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/simpledali/websocketdali.py", line 50, in parseResponse
    response = await self.ws.recv()
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 552, in recv
    await self.ensure_open()
  File "/opt/homebrew/Caskroom/miniforge/base/envs/simpledali/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 929, in ensure_open
    raise self.connection_closed_exc()
websockets.exceptions.ConnectionClosedError: sent 1002 (protocol error); no close frame received

Note this is in STREAM mode, but where no data is flowing. The Datalink protocol says:

No client commands are accepted in streaming mode except ID requests

so techinically this is ok by websockets, but prohibited by datalink. I think it would be good to handle when doing web sockets, and maybe allow PING-PONG for normal sockets would be useful too?

[chad-earthscope]

I think it would be good to handle when doing web sockets,

Agreed. Got a repeatable test?

and maybe allow PING-PONG for normal sockets would be useful too?

That is why the ID is an exception, i.e so it can be used for pings.

[crotwell]

Yep, what I meant was once you enable it for websockets, it should be trivial to let a regular socket use the same PING PONG messages. I agree it doesn;t really do anything that ID doesn't, just for consistency between the two types of connections.

[crotwell]

Actually, ping-pong, because it is embedded in the websocket frame doesn't really make sense for plain sockets. Pretend I never said anything about it...

[crotwell]

Repeatable test case would be like
readdali.py

Start up an otherwise empty ringserver,
edit connection params in readdali.py to connect to it (ie host and port),
change line 18-19 in readdali.py so that ping_interval is not None, like
ping_interval=5

run readdali.py and wait for 5 seconds, barf will occur.