Setting the DHCP Hostname

[brokenbrigde9000]

I'm running v1.20.0 on an ESP32 and try to change the device name which shows up at the wifi router it connects to. I see a couple of posts that state you can use .config(dhcp_hostname='insert_hostname_here'. I use this sequence:

# cfg has the wifi credentials
ssid = cfg['wifi_ssid']
password = cfg['wifi_pw']
hname = cfg['device_id'] # identify the device with this hostname

station = network.WLAN(network.STA_IF)
station.active(True)
station.config(dhcp_hostname=hname)    
station.connect(ssid, password)

unfortunately, using dhcp_hostname= gives me 'ValueError:'. Is this functionality not available for the ESP32? Maybe it is defined differently and I'm using the wrong parameters?

[jimmo]

Setting dhcp_hostname raises ValueError if the hostname is too long.

In v1.20 we made this parameter work the same across all ports (which imposes a maximum length of 15), but I think previously the ESP32 version allowed a longer hostname.

[brokenbrigde9000]

Perfect, that works like a charm! Is there any place I can find information like that written down? I could not find this in the docs.

[Josverl]

the same across all ports

Does that include rp2 with w5500?

Happened to try that yesterday and it failed, I'll double check the host name for dns/dhcp compliance

[Josverl]

@jimmo, The Wiznet 5500 on v1.20.0 does not recognize dhcp_hostname.
precomiled firmware: MicroPython v1.20.0 on 2023-04-26; W5500-EVB-Pico with RP2040

[glenn20]

Possibly related (re. hostname support for wiznet on ESP32): #11541.

[jimmo]

@Josverl I don't think this is supported on the Wiznet driver yet.

Also network.hostname() is (since v1.20) the preferred way to set the hostname (and will apply to all NIC types that support it).

[massimosala]

Hi Jim

I cannot set the hostname, neither with network.hostname nor dhcp_hostname in STA_IF.

Please see my last comment:
#11450

[divergentti]

I did not know about 15 chars limit for the dhcp name. Is there other limitations?

I just rewrote my asynchonous driver, which tries to connect to 2 predefined APs -> [GitHub] (https://github.com/divergentti/Micropython-for-ESP32/blob/main/esp32-bme680-oled/drivers/WIFICONN_AS.py) and perhaps I shall add more error checking to the code.

[liudr]

IIRC, as an ESP-IDF developer in my past life, this limit is 30 or 31 in ESP32. I had azure IoT device names in 32-char alphanumerical sequences that I had to shorten slightly to fit. I also found out while doing some tests. 15 chars are barely 2 words and a short number. What is the reason for shortening this? Can I change the port or the main mp to increase back to say 30 so I can compile custom firmware? Thanks.

[jimmo]

See MICROPY_PY_NETWORK_HOSTNAME_MAX_LEN

[liudr]

Thanks @jimmo
I tried including MICROPY_PY_NETWORK_HOSTNAME_MAX_LEN=31 in sdkconfig.board and there was no effect.
I found a way to add compiler options in mpconfigboard.cmake as the following and it does take effect. I checked on my router with up to 30 chars when defining 31. I think the last byte is \0.

add_compile_definitions(MICROPY_PY_NETWORK_HOSTNAME_MAX_LEN=31)

Interesting tidbit:

This def is in modnetwork.h with an #ifndef and a default value of 16. Then in relevant files >=MICROPY_PY_NETWORK_HOSTNAME_MAX_LEN is considered valueError:

        if (len >= MICROPY_PY_NETWORK_HOSTNAME_MAX_LEN) {
            mp_raise_ValueError(NULL);
        }

So mp has a bunch of C function calls like mp_raise_ValueError() instead of C++ member functions?