Client Server with ESP32

[A622266]

I am trying to generate a signal on the ESP32 (the client) and to send it to a python script on a host PC (the server). On my home network, the host PC is on 192.168.1.22. The protocol is UDP, and the server listens on port 56000 for any data. The following code implements the server running on the PC:

#  This is the server in CPython
import socket
port = 56000
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind(("", port))
print(f"waiting on port: {port}")
while 1:
	data, addr = s.recvfrom(1024)
	print(data)

The client connects to the network on address 192.168.1.11, and sends data using port 56000. esp_network is a function to connect the esp32 to the network. make_tone is a function derived from the play_tone example from Mike Teachman's i2s-examples. The following code implements the client running on the esp32:

# this is the client in micropython
import usocket as socket
import esp_network
import make_tone

esp_network.do_connect()

# ======= AUDIO CONFIGURATION =======
TONE_FREQUENCY_IN_HZ = 5000
SAMPLE_SIZE_IN_BITS = 16
SAMPLE_RATE_IN_HZ = 48_000
# ======= AUDIO CONFIGURATION =======

ADDR = "192.168.1.11"      # This is IP of the server
PORT = 56000

# Socket to exchange data with GR
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

while True:
    samples = make_tone.make_tone(SAMPLE_RATE_IN_HZ, 
        SAMPLE_SIZE_IN_BITS, TONE_FREQUENCY_IN_HZ)
    print(samples)
    s.sendto(samples, (ADDR, PORT))

The esp32 successfully connects to the network on 192.168.1.11. samples is successfully generated as a bytearray, and generally the client appears to work. However, the server does not receive the samples. I tried changing ADDR to be 192.168.1.22, but I get an error: OSError: [Errno 12] ENOMEM.

Can anyone see my error, or make a suggestion of something to try?

[davefes]

Try printing the addr in the server while loop to confirm.

I do something similar but send a message from the server, then at the client get the server's address. Then you can print it out to confirm that you have a working link.

[A622266]

Okay I'll look into the matter of 2 way comms for UDP -- I don't think it should be required, but better to verify. Can you check the link? It does not appear to work..

[davefes]

Hmmm ... is:

s.recvfrom(1024)

too small? Try increasing it and when that fails you will probably need to do some reading on how to deal with continuous data. I haven't done that yet.

[davefes]

https://stackoverflow.com/questions/56951343/send-continuous-data-in-python-with-udp-socket
See last comment.

[davefes]

I always send a reply back to the server to ACK correct reception. Sounds like a step towards TCP!

[davefes]

Ctrl + K and Ctrl + C, according to the GitHub docs
https://stackoverflow.com/questions/56951343/send-continuous-data-in-python-with-udp-socket
OK I give up. How does one add a link?

[davefes]

Looks like I don't how to add links correctly! Copy/paste and see if that works.

[A622266]

on the links: you use the little icon 6th from the left that looks like a chain. You highlight a word like Wikipedia, and then past the url into the highlighted section that shows up after you click the icon.
I think you are onto something. If I make the server buffer bigger, I do get some data transfers before crashing! Probably I need a correct buffer size and a correct way of handling continuous data..

[davefes]

That is what I was doing in the first place :) Ah, when you highlight the link icon it actually says Ctrl K, so I didn't need to go searching the docs.
Maybe, it is a Ubuntu thing.

[A622266]

Okay I think I have a path now, thanks to help from davefes. The server buffer size matters to make sure you capture all the data sent, but it doesn't appear to cause the crash. The crash is caused by not having a delay in the while loop at client -- so I suppose if the data sent is more than the esp32 wifi can keep up with, there is a crash. If I add a delay as follows:

while True:
    samples = make_tone.make_tone(SAMPLE_RATE_IN_HZ, 
        SAMPLE_SIZE_IN_BITS, TONE_FREQUENCY_IN_HZ)
    print(samples)
    s.sendto(samples, (ADDR, PORT))
    time.sleep(0.1)

There is no crash, and the server receives the data. I'm not sure I can do what I want to do, which is to send audio data in real time over the wifi. If the data is 16-bit, at 48khz sample rate, that's 768kpbs worst case. Can anyone comment on if this is too fast?

[davefes]

I would suggest marking this answered and start a new thread. Also, I get many of my socket-related answers on stackoverflow.

[A622266]

agreed, thanks for your help!