mDNS safe mode - find

[anecdata]

CircuitPython version

Adafruit CircuitPython 7.3.0-alpha.0-52-g4465adfe0 on 2022-03-21; FeatherS2 with ESP32S2
(this is the version that corresponds to the mDNS merge)

Code/REPL

import wifi
import mdns
from secrets import secrets

print(" Connecting", end="\r")
wifi.radio.connect(secrets['ssid'], secrets['password'])
print(wifi.radio.ipv4_address)

print("Starting mDNS server...")
server = mdns.Server(wifi.radio)
service_types = ("_http", )

protocols = ("_tcp", )
for service_type in service_types:
    print(service_type, end=" ")
    for protocol in protocols:
        print(protocol)
        remote_service_tuple = server.find(service_type=service_type, protocol=protocol, timeout=5)
        for remote_service in remote_service_tuple:
            print(remote_service.hostname, remote_service.instance_name, remote_service.service_type, remote_service.protocol, remote_service.port)

Behavior

The example code probably works in many environments, but Safe Mode occurs when substituting many other service types and protocols. Hypothesis is there are no results for that combination.

code.py output:
Connected.    
Starting mDNS server...
_upnp _udp

[tio 21:28:16] Disconnected
[tio 21:28:20] Connected
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Crash into the HardFault_Handler.
Please file an issue with the contents of your CIRCUITPY drive at 
https://github.com/adafruit/circuitpython/issues

Press any key to enter the REPL. Use CTRL-D to reload.

Description

Pattern seems to be Safe Mode when trying to find a service type and protocol that do not exist on the network.

Additional information

No response

[tannewt]

What exact code are you running? The prints don't match the code. (udp vs tcp).

I'm able to run a modified version ok:

code.py output:
192.168.1.94
Starting mDNS server...
_http _tcp
BRW7429AF6E7F02 Brother HL-L2340D series _http _tcp 80
_udp
_upnp _tcp
_udp

My version:

import wifi
import mdns

print(" Connecting", end="\r")
wifi.radio.connect("ssid", "password")
print(wifi.radio.ipv4_address)

print("Starting mDNS server...")
server = mdns.Server(wifi.radio)
service_types = ("_http", "_upnp" )

protocols = ("_tcp", "_udp")
for service_type in service_types:
    print(service_type, end=" ")
    for protocol in protocols:
        print(protocol)
        remote_service_tuple = server.find(service_type=service_type, protocol=protocol, timeout=5)
        for remote_service in remote_service_tuple:
            print(remote_service.hostname, remote_service.instance_name, remote_service.service_type, remote_service.protocol, remote_service.port)

[anecdata]

That's the right code (well, I changed it to print the IP address when connected). If I run that code above as-is, it works, but, for example, _http _udp, or _upnp _tcp, crashes.

[tannewt]

I wonder if it is an S2 vs S3 thing. I tested on S3s. I also tested with a later version off main.

[tannewt]

I've replicated this on an S2.

[anecdata]

S3 is quirky too, but I think PR fix will fix S3 also. Thanks!

I often put a while True: loop after test code (with a pass or a sleep or a print) because I don't want to immediately drop into the REPL, partially since sometimes memory effects can take a moment to manifest. On S3, the non-existent checks would not crash immediately, but would either reset the serial connection or safe mode after entering the while loop.

[tannewt]

Makes sense. I'm surprised the S3 doesn't crash...