How to set hostname properly?

[cziter15]

Hello,

How to trigger hostname setting properly using WiFi class / station mode?
Should setHostname be called before WIFI_STA mode set (or begin)? Or after?

I'm playing with this functionality and getting mixed results. Why i have to call wifi_station_set_hostname to get it working?

WiFi.mode(WIFI_STA);
WiFi.setHostname(hostname);
wifi_station_set_hostname(hostname);

Without calling wifi_station_set_hostname or changing the order, it fallbacks to ESP-XXXXX hostname. Looks like something broken recently.

[mcspr]

Have you checked whether setHostname(...) returns true or tried enabling debugging?
What hostname string are you trying to set?

I see that our hostname func might be picky about format. But, it does not depend on interface being up

Arduino/cores/esp8266/LwipIntf.cpp

Lines 119 to 198 in 39b4137

	bool LwipIntf::hostname(const char* aHostname)
	{
	/*
	vvvv RFC952 vvvv
	ASSUMPTIONS
	1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
	to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
	sign (-), and period (.). Note that periods are only allowed when
	they serve to delimit components of "domain style names". (See
	RFC-921, "Domain Name System Implementation Schedule", for
	background). No blank or space characters are permitted as part of a
	name. No distinction is made between upper and lower case. The first
	character must be an alpha character. The last character must not be
	a minus sign or period. A host which serves as a GATEWAY should have
	"-GATEWAY" or "-GW" as part of its name. Hosts which do not serve as
	Internet gateways should not use "-GATEWAY" and "-GW" as part of
	their names. A host which is a TAC should have "-TAC" as the last
	part of its host name, if it is a DoD host. Single character names
	or nicknames are not allowed.
	^^^^ RFC952 ^^^^
	- 24 chars max
	- only a..z A..Z 0..9 '-'
	- no '-' as last char
	*/
	size_t len = strlen(aHostname);
	if (len == 0 || len > 32)
	{
	// nonos-sdk limit is 32
	// (dhcp hostname option minimum size is ~60)
	DEBUGV("WiFi.(set)hostname(): empty or large(>32) name\n");
	return false;
	}
	// check RFC compliance
	bool compliant = (len <= 24);
	for (size_t i = 0; compliant && i < len; i++)
	if (!isalnum(aHostname[i]) && aHostname[i] != '-')
	{
	compliant = false;
	}
	if (aHostname[len - 1] == '-')
	{
	compliant = false;
	}
	if (!compliant)
	{
	DEBUGV("hostname '%s' is not compliant with RFC952\n", aHostname);
	}
	bool ret = true;
	strcpy(wifi_station_hostname, aHostname);
	// now we should inform dhcp server for this change, using lwip_renew()
	// looping through all existing interface
	// harmless for AP, also compatible with ethernet adapters (to come)
	for (netif* intf = netif_list; intf; intf = intf->next)
	{
	// unconditionally update all known interfaces
	intf->hostname = wifi_station_hostname;
	if (netif_dhcp_data(intf) != nullptr)
	{
	// renew already started DHCP leases
	err_t lwipret = dhcp_renew(intf);
	if (lwipret != ERR_OK)
	{
	DEBUGV("WiFi.hostname(%s): lwIP error %d on interface %c%c (index %d)\n",
	intf->hostname, (int)lwipret, intf->name[0], intf->name[1], intf->num);
	ret = false;
	}
	}
	}
	return ret && compliant;
	}

Using SDK func just goes around that filtering, but you have to enable WiFi before it works (unlike our method)

[cziter15]

Need to debug it, but to do it I need to get a board on my desk. Now the device is mounted.

Anyway, yes I've read that code. It worked earlier, but after updating arduino and switching to sdk 3.0.5 the behavior has changed.

The name is Raesp in this case, it should work.

[mhightower83]

In the past, I have also had this issue. It initially wasn't clear to me what I did that fixed it. I now think these are some additional key components to make it work:

• I think it is key to start from the WL_IDLE_STATUS state. Make sure the ESP is not using remembered SSID and password.
• WiFi.hostname(aHostname) must precede WiFi.begin()
• The Router needs to support registering DHCP host names from clients into the active local DNS resolver.

Also for me, it works with SDK v3.0.5.

[cziter15]

Well this is very strange how it behaves.

My current implementation:

  // somewhere at initialization
  WiFi.mode(WIFI_STA);
  hostNameChanged = WiFi.setHostname("Raesp");
  setupMacAddress();
  WiFi.setAutoConnect(false);
  WiFi.setAutoReconnect(false);

  // post initialization
  WiFi.begin();

Then asking for hostname (later):

respond(
	PGM_("HNC: ") + std::to_string(hostNameChanged ) + 
	PGM_(", HN: ") + WiFi.getHostname()
);

and it responds
HNC: 1, HN: ESP-7800CB.

Well it says that the setHostname returned true, but when asking for hostname it remains unchanged/default.
Anyway, I'm unable to erase SSID/PWD as I'm using this feature (this is how WiFiManager handles provisioning persistence).

It looks like some other function overrides that hostname... but what function? Maybe esp sdk?

[cziter15]

Will try later today. I've fixed my library so now it doesn't block loop anymore. Everything seems to be working properly now.

Is it allowed from Arduino-esp8266 perspective to "expropriate" the loop function and call own while loop with yield/delay inside or not? What about writing own main?

[d-a-v]

Then do not try #8825, it breaks the protocol which is otherwise working without this patch.
Thanks for your report !

[cziter15]

I've flashed my boards yesterday and currently using ArduinoOTA.begin with hostname (everything before actually connecting to WiFi) and mDNS is properly responding (>10h uptime).

@d-a-v, Are you able to answer the question about blocking inside loop? A lot of people do delays inside loop, which may break mDNS respoder as we see right now.

[d-a-v]

On esp8266, blocking inside a loop will not allow services to work properly.
Any service needing a regular call like .update(), .loop(), .handleClients() and also WiFi and mandatory IP services can be impacted, especially when this kind of loop is done inside an external library not aware of other existing services.

Using recurrent scheduled functions might help since core version 3.1 as they are now also called from delay(n) but always in "cont" mode (= not in system or OS or interrupt mode = anything except delay()/yield() is allowed).
They can be used like Ethernet does.
We've not tried yet to extensively use them for our core services (except for Ethernet), but you can try with mDNS and report if it is working for you.

Note: this is not portable and very specific to esp8266 arduino core.

[cziter15]

Thank you for the answer 👍. I've clossed this discussion with tl;dr as everything asked seems to be answered.

[hmueller01]

I was struggling here too.
I use

  Serial.println(WiFi.getHostname());
  WiFi.mode(WIFI_STA);
  WiFi.setHostname("myESP");
  ...
  WiFi.begin();
  Serial.println(WiFi.getHostname());
  ArduinoOTA.begin();
  Serial.println(WiFi.getHostname());

I get

ESP-6A4C81
myESP
myESP

But in my router I see
esp8266-6a4c81
Why is ArduinoOTA not using the WiFi.setHostname?

  if (!_hostname.length()) {
    char tmp[15];
    sprintf(tmp, "esp8266-%06x", ESP.getChipId());
    _hostname = tmp;
  }

if not explicit set with ArduinoOTA.setHostname("myESP");?

[cziter15]

This is normal, esp32 implementation works same way. If you want ArduinoOTA to pass mDNS hostname to the mDNS service, just use begin function variant with hostame parameter.

About automatically copying hostname from WiFi interface, well, might be good topic to discuss... but there are other OTA implementations (for example you can have Ethernet controller and then there's a question which hostname should be used for mDNS).

[hmueller01]

Tx for the quick reply.
I think begin() is not valid, as begin is defined in ArduinoOTA:
void begin(bool useMDNS = true);

Have to use ArduinoOTA.setHostname("myESP")

//Sets the device hostname. Default esp8266-xxxxxx
    void setHostname(const char *hostname);

Right. I was only thinking about WiFi ... so using WiFi.getHostname() might not be a final solution.

But without this discussion I would never have found the source of this behavior ... (and I doubt others would).
And maybe it is good to rethink the current solution ...

[d-a-v]

DNS hostname and mDNS hostname are independant and unrelated on the network.

The first is given by the DNS server which is often a service proposed by the DHCP server on home routers.
The hostname "offered" by the esp (= dhcp client) is that one.
For this reason, WiFi.hostname("name") should be called before starting WiFi.begin() which sends the hostname proposal to the DHCP (and possibly DNS) server.

This is often difficult to manage for users (user knowledge or configuration options out of reach in some network infra).
So mDNS has been created which requires no user configuration in network servers / services.
There is no "network mDNS server". There are only devices talking each other and agreeing on name unicity on the LAN.

But in my router I see esp8266-6a4c81

You router seems to show you the mDNS name configured by Arduino OTA.
If you want to change it, call ArduinoOTA.setHostname("name") before ArduinoOTA.begin().

On the contrary my router shows me the Network name (DNS).
My computer resolve both with DNS service and mDNS service. On linux, priority is defined by /etc/nsswitch.conf. Don't ask me about windows.

So best practice would be:

WiFi.hostname("name");
ArduinoOTA.setHostname("name");
WiFi.begin();
ArduinoOTA.begin();

About automatically copying hostname from WiFi interface, well, might be good topic to discuss...

True.
esp8266 ArduinoOTA API has not changed for a while and it could take WiFi hostname instead of esp8266-xxxxx by default when uninitialized. In the past, default WiFi hostname format was not network compliant, but now it is.

[cziter15]

Tx for the quick reply. I think begin() is not valid, as begin is defined in ArduinoOTA

My bad. Yeah, I meant setHostname before begin.

[cziter15]

TL;DR

• Hostname should be set before calling WiFi.begin(), preferably with WiFi mode set to WIFI_STA (and WIFI_OFF on ESP32).
• The hostname set by WiFi.setHostname has nothing to do with mDNS hostname.
• Your code shouldn't stuck in loop(), even when you call handle() and similar methods manually as some services are handled after returning from loop function. Calling delay(1) or yield() is not a magic solution. See: How to set hostname properly? #8816 (reply in thread)