MicroPython Forum (Archive)

Posted: **Thu Nov 25, 2021 5:38 pm**

I have an ESP32 board running MP 1.17. I use urequests to get and post to a server on my local network So far if I give it an ip address such as 192.168.0.123, it works. If I post to a remote host with address like abc.duckdns.org, it works too. This means MP successfully did domain name lookup, I guess.

But, I installed a Debian machine and left it with a default domain name "debian". On PC, using requests, I was able to reach it by just providing debian as address. I was also able to reach debian's web server with http://debian in my address bar on firefox as well.

But, if I use debian as address for ESP32, it reports an error:

Code: Select all

>>> import usocket
>>> usocket.getaddrinfo('debian', 80, 0, usocket.SOCK_STREAM)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: -202
>>> usocket.getaddrinfo('192.168.0.191', 80, 0, usocket.SOCK_STREAM)
[(2, 1, 0, '192.168.0.191', ('192.168.0.191', 80))]
>>>

As you can see above, looking up debian failse with -202, while looking up an ip address got the right response.

I wonder if this is only on ESP32 port or all MCU ports.

I also installed the unix port on my debian machine using a snap command. Did the same test and seems fine:

Code: Select all

>>> import usocket
>>> usocket.getaddrinfo('debian', 80, 0, usocket.SOCK_STREAM)
[(2, 1, 6, None, bytearray(b'\x02\x00\x00P\x7f\x00\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00'))]
>>> usocket.getaddrinfo('192.168.0.191', 80, 0, usocket.SOCK_STREAM)
[(2, 1, 6, None, bytearray(b'\x02\x00\x00P\xc0\xa8\x00\xbf\x00\x00\x00\x00\x00\x00\x00\x00'))]

Posted: **Thu Nov 25, 2021 6:02 pm**

One improvement:

I renamed my debian machine to debian.local. This passed the getaddinfo()

Code: Select all

>>> import usocket
>>> usocket.getaddrinfo('debian.local', 80, 0, usocket.SOCK_STREAM)
[(2, 0, 0, 'debian.local', ('192.168.0.191', 80))]

But I still can't get requests.get() to work:

Code: Select all

>>> import urequests as requests
>>> results=requests.get('http://debian.local:80')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "urequests.py", line 116, in get
  File "urequests.py", line 58, in request
OSError: [Errno 22] EINVAL

Again I tested with IP address and it works:

Code: Select all

>>> results=requests.get('http://192.168.0.191:80')
>>> results
<Response object at 3f82e0c0>
>>> results.content
b'\n<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.

Posted: **Thu Nov 25, 2021 7:01 pm**

.local is a mDNS/DNS-SD thing (aka Bonjour). Trying to resolve it from a client that doesn't know these protocols won't work.

Your Debian box will have avahi running, which is doing all the multicast DNS magic for you.

Posted: **Thu Nov 25, 2021 7:50 pm**

OK, so I was going through the source code of urequests, specifically request():

https://github.com/micropython/micropyt ... equests.py

I followed its logic in REPL more or less but didn't do the " s = ussl.wrap_socket(s, server_hostname=host)" line. That might be the source of the problem when I supplied a "debian.local".

So what I did was to call usocket.getaddrinfo(host, port, 0, usocket.SOCK_STREAM) to return the (ip address, port) tuple and replaced the "debian.local" with this ip address. Then it works.

Posted: **Thu Nov 25, 2021 8:02 pm**

scruss wrote: ↑
Thu Nov 25, 2021 7:01 pm
.local is a mDNS/DNS-SD thing (aka Bonjour). Trying to resolve it from a client that doesn't know these protocols won't work.

Your Debian box will have avahi running, which is doing all the multicast DNS magic for you.

Thanks scruss. I figured out the issue was the return values of getaddrinfo ai[1] passed to s = usocket.socket(ai[0], ai[1], ai[2])

If you see the results I got with "debian.local" vs "192.168.0.191", the value ai[1] is 0 in former and 1 in latter (2,0,0) vs (2,1,0):

Code: Select all

>>> usocket.getaddrinfo('debian.local', 80, 0, usocket.SOCK_STREAM)
[(2, 0, 0, 'brain.local', ('192.168.0.191', 80))]

>>> usocket.getaddrinfo('192.168.0.191', 80, 0, usocket.SOCK_STREAM)
[(2, 1, 0, '192.168.0.191', ('192.168.0.191', 80))]

I wish I knew what that value means. It's used to create a socket and that fails.

Posted: **Fri Nov 26, 2021 10:48 pm**

liudr wrote: ↑

Thu Nov 25, 2021 8:02 pm

Code: Select all

>>> usocket.getaddrinfo('debian.local', 80, 0, usocket.SOCK_STREAM)
[(2, 0, 0, 'brain.local', ('192.168.0.191', 80))]
>>> usocket.getaddrinfo('192.168.0.191', 80, 0, usocket.SOCK_STREAM)
[(2, 1, 0, '192.168.0.191', ('192.168.0.191', 80))]

This looks like a bug for me.
I will have to dig out one of my ESPs to confirm this, but the first call returns a SOCK_DGRAM (contrary to the requested SOCK_STREAM in the getaddrinfo() call) in the second element of the outer tuple.
Most likely, the socket.connect() will succeed, but it will not be useable for a HTTP request.

What is your exact micropython version and ESP variant?
Did you compile yourself (if yes: with which ESP-IDF version) or are you using a prebuilt image ?

Posted: **Fri Nov 26, 2021 10:54 pm**

1.17 released version for ESP32 generic with SPIRAM
Thanks for looking over it.

Posted: **Sat Nov 27, 2021 10:45 am**

I just added the following issues:

However, it might last weeks/months/years until this gets fixed.

For your urequest problem, there is an easy workaround:
in urequest.py the socket gets created as

Code: Select all

    
    ai = usocket.getaddrinfo(host, port, 0, usocket.SOCK_STREAM)
    ai = ai[0]

    s = usocket.socket(ai[0], ai[1], ai[2])
    try:
        s.connect(ai[-1])

You can change the socket() call to

Code: Select all

    s = usocket.socket(ai[0], usocket.SOCK_STREAM, ai[2])

Regards,
Thomas

Posted: **Sun Nov 28, 2021 5:25 pm**

Thanks @karfas for raising the issues for me. From my tests, calling getaddrinfo() if the host name is just "debian" caused exceptions so I went for a dotted name and that got me past getaddrinfo(). So I first call this and then extract the number-dot IP address and use that to call request().

It would be nice to resolve this problem in urequests though.

MicroPython Forum (Archive)

Resolving local network domain name

Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name

Re: Resolving local network domain name