Uasyncio StreamReader socket and uart togheter, data loss.

[prem111as]

Hello. I am using two StreamReader streams, one for UART the other for Socket udp. If there is a lot of data from UART, unfortunately I lose UDP packets. Is there any solution for this?

Regards.

[sophiedegran]

Hi
Did you look at auart.py from Peter on github.com/peterhinch/micropython-async/v3/as_demos ?

[sophiedegran]

Nn by Queuing I would say buffering ☺
Look at Peter examples on primitives queue.py and ringbuf_queue.py

[prem111as]

Can I find examples of using these classes somewhere? I have one more question, when I skip StreamReader and read directly from sock.recv() it gets all the data. Unfortunately the loop hangs when the udp device stops responding, can I use something to prevent blocking?

[sophiedegran]

Yes look at the TUTORIAL.md in /docs it look a little 'hard' to use primitives from Peter but it's not...
Take your time you find the problem
1- async read uart
2- async queue
3- async serve udp

[prem111as]

Thanks ! Can you tell me something about my second question about socket and blocking ?

[bixb922]

If UDP blocks for a longer time, asyncio cannot serve the UART queue and it will overflow, and characters will be lost.

Some options:
Option 1. Use non blocking sockets and check the socket for example every 20 milliseconds waiting with asyncio.sleep_ms. This is the simplest option, except if the UDP messages were very, very time critical

Option 2. Start a _thread for the code related to the socket. Coordination with the asyncio code for the UART can be a bit tricky, by all means see https://github.com/peterhinch/micropython-async/blob/master/v3/docs/THREADING.md

Option 3. There may be some asyncio UDP library out there.

[prem111as]

There is one more thing. Why is it that when I receive a socket stream via StreamReader, when I disconnect the device that serves data via udp, UART reading does not block, and when I getting data directly from sock.recv, it blocks when disconnect device. s there any way to prevent sock.recv from blocking?

[sophiedegran]

Is that the code you send above? If so make an exception in your while..

[prem111as]

Yes its it. What exactly do you mean about exception in while ? can you give an example? in my case, when the device that serves UDP is disconnected, the loop just hangs and is blocked on sock.recv..... I know I can use settimeout, but I would like to avoid it ( I would like this async task to be independent of what happens in the sock, whether it is blocked or not )

[sophiedegran]

If I understand you il the server stop sending udp it's hang on your client (code above) and you should have an exception on it?

[prem111as]

Yes, exactly. This is what happens, when the udp server stops sending, my sock.revc loop hangs, it blocks, and I don't want that, I don't want blocking.

[sophiedegran]

Look at bixb answer.. (THREADING.md)
For me:
1- put the udp receiver in async mode (it is not)
2- try to have an exception in your context (should not block)

[sophiedegran]

You're listening all broadcast udp ! Listen only your server..
You receive all dns call, etc...

[prem111as]

Server sent multicast messages, but even when I specify sock.bind(('192.168.0.1', 4444)) and setblocking(False) i given the same error: [Errno 11] EAGAIN

[sophiedegran]

Why you do that? Do a connexion point to point ..
Server should listening on 4444 and client reading the 4444 of the server
On broadcast you have many things.. dns, discovery..
Perharps put your server in AP mode and try with the client connected on it.. and increase the socket.recv () still you have not resolve that

[prem111as]

I don't understand, the server sends multicast messages to a specific port, how should I connect point to point? Can you provide example code, what do you mean?

[bixb922]

When use sock.setblocking(False) i given error: [Errno 11] EAGAIN

~10 messages per second.

Yes, that means that there is no data when the receive is executed. Trap the exception and await asyncio.sleep_ms(something) between each retry