Espressif ESP32 Core 3.1.1 Why ping by name is Ko ?

Projects Networking, Protocols, and Devices
1

My environment:
Arduino IDE V1.8.19
Preferences : https://arduino.esp8266.com/stable/package_esp8266com_index.json,https://espressif.github.io/arduino-esp32/package_esp32_index.json
Library esp32 by Espressif Systems v3.1.1

Hostname : Seems to be ok (not too long, no special characters)
Some documentation says that hostname must be set before calling WiFi.mode and WiFi.begin
Adding or not WiFi.config : nothing change
A try with an ESP8266 NodeMCU V1.0 (with another code ...) it's ok to ping the module by it's name

Connection to WiFi : Ok
Ping by IP : Ok
ping 192.168.1.87
PING 192.168.1.87 (192.168.1.87) 56(84) bytes of data.
64 bytes from 192.168.1.87: icmp_seq=1 ttl=64 time=146 ms

Ping by hostname : Ko
ping ESP32TEMP
ping: ESP32TEMP: Nom ou service inconnu

Test code

#include <WiFi.h>

// Replace with your network credentials (STATION)
// const char* ssid = "REPLACE_WITH_YOUR_SSID";
// const char* password = "REPLACE_WITH_YOUR_PASSWORD";

String hostname = "ESP32TEMP";

void initWiFi() {

  // With or without WiFi.config : no change
  // WiFi.config(INADDR_NONE, INADDR_NONE, INADDR_NONE, INADDR_NONE);
  WiFi.setHostname(hostname.c_str()); //define hostname
  
  WiFi.mode(WIFI_STA);
  
  // WiFi.config(INADDR_NONE, INADDR_NONE, INADDR_NONE, INADDR_NONE);
  // WiFi.setHostname(hostname.c_str()); //define hostname
  
  //wifi_station_set_hostname( hostname.c_str() );
  WiFi.begin(ssid, password);
  Serial.print("Connecting to WiFi ..");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(1000);
  }
  Serial.println(WiFi.localIP());
}

void setup() {
  Serial.begin(115200);
  initWiFi();
  Serial.print("RSSI: ");
  Serial.println(WiFi.RSSI());
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(1000);
  Serial.print(WiFi.getHostname());
  Serial.println(" Ok");
}

Monitor : ESP32TEMP Ok

A scan network with nmap

nmap -sL 192.168.1.*

Nmap scan report for ESP32TEMP (192.168.1.87)

I can't find any solution to my problem. Thank you in advance.

2

Try adding ".local" to the hostname with nmap and ping.
I use character arrays rather than String.

Edit: Here is the difference. My RPi hostname is raspberrypi.

tim@tim2:~$ ping raspberrypi
ping: raspberrypi: Temporary failure in name resolution

tim@tim2:~$ ping raspberrypi.local
PING raspberrypi.local (192.168.1.22) 56(84) bytes of data.
64 bytes from 192.168.1.22 (192.168.1.22): icmp_seq=1 ttl=64 time=0.583 ms
3

Hum ...
Thanks for your request

You can access with .local when you use

#include <ESPmDNS.h>

void setup()
{
  ...

 if(!MDNS.begin(hostname)) { // your custom hostname
    Serial.println("Error starting mDNS");
 }
}

But with only adding .local to the hostname , the ping is Ko.

And the use of ESPmDNS the http Request like http://"hostname".local on my ESP32 seems random ok with an http code 200 and ko with code -1
The same request with the IP of my ESP32 it is always good
This is why I excluded the use of mDNS and i want to use the hostname

There is a problem with the ESP32 but I don't know if it's my code that is not good or if the problem is in the WiFi library and the ESP32.

4

As I recall, the ".local" extension tells ping and nmap to use an arp scan rather than DNS.

5 
ESP32 Code :
String hostname = "ESP32TEMP";

nmap result:
Nmap scan report for ESP32TEMP (192.168.1.87)

ping result:

ping ESP32TEMP.local
ping: ESP32TEMP.local: Nom ou service inconnu

Indeed, ping seems not to make the same request because it takes longer to respond but the result is the same.

6

That part may be a challenge with your code or the library.
I( presume this means "Name or service unknown"

Nom ou service inconnu

Edit: Here's an oddity. My RPi doesn't need the ".local" extension to use an arp scan.
I was testing on a Ubuntu box. It may just be the way your OS does the ping and nmap.

Edit2: I was wrong. the ".local" extension is still needed with ping and nmap on my RPi. You don't need the extension if the hostname is localhost (same computer).

7

All the verbose debug at startup ...

ets Jul 29 2019 12:21:46

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0030,len:4916
load:0x40078000,len:16436
load:0x40080400,len:4
ho 8 tail 4 room 4
load:0x40080404,len:3524
entry 0x400805b8
[     1][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RX (2) successfully set to 0x400d983c
[    12][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_TX (3) successfully set to 0x400d980c
[    26][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_CTS (4) successfully set to 0x400d97dc
[    39][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RTS (5) successfully set to 0x400d97ac
[    53][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RX (2) successfully set to 0x400d983c
[    66][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_TX (3) successfully set to 0x400d980c
[    80][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_CTS (4) successfully set to 0x400d97dc
[    93][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RTS (5) successfully set to 0x400d97ac
[   107][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RX (2) successfully set to 0x400d983c
[   120][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_TX (3) successfully set to 0x400d980c
[   134][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_CTS (4) successfully set to 0x400d97dc
[   147][V][esp32-hal-periman.c:235] perimanSetBusDeinit(): Deinit function for type UART_RTS (5) successfully set to 0x400d97ac
[   187][D][esp32-hal-cpu.c:263] setCpuFrequencyMhz(): PLL: 480 / 2 = 240 Mhz, APB: 80000000 Hz
[   224][V][esp32-hal-periman.c:160] perimanSetPinBus(): Pin 3 successfully set to type UART_RX (2) with bus 0x3ffbdb74
[   235][V][esp32-hal-periman.c:160] perimanSetPinBus(): Pin 1 successfully set to type UART_TX (3) with bus 0x3ffbdb74
=========== Before Setup Start ===========
Chip Info:
------------------------------------------
  Model             : ESP32
  Package           : D0WD-Q5
  Revision          : 3.01
  Cores             : 2
  CPU Frequency     : 240 MHz
  XTAL Frequency    : 40 MHz
  Features Bitfield : 0x00000032
  Embedded Flash    : No
  Embedded PSRAM    : No
  2.4GHz WiFi       : Yes
  Classic BT        : Yes
  BT Low Energy     : Yes
  IEEE 802.15.4     : No
------------------------------------------
INTERNAL Memory Info:
------------------------------------------
  Total Size        :   336808 B ( 328.9 KB)
  Free Bytes        :   296580 B ( 289.6 KB)
  Allocated Bytes   :    32964 B (  32.2 KB)
  Minimum Free Bytes:   290708 B ( 283.9 KB)
  Largest Free Block:   110580 B ( 108.0 KB)
------------------------------------------
Flash Info:
------------------------------------------
  Chip Size         :  4194304 B (4 MB)
  Block Size        :    65536 B (  64.0 KB)
  Sector Size       :     4096 B (   4.0 KB)
  Page Size         :      256 B (   0.2 KB)
  Bus Speed         : 80 MHz
  Bus Mode          : QIO
------------------------------------------
Partitions Info:
------------------------------------------
                nvs : addr: 0x00009000, size:    20.0 KB, type: DATA, subtype: NVS
            otadata : addr: 0x0000E000, size:     8.0 KB, type: DATA, subtype: OTA
               app0 : addr: 0x00010000, size:  1280.0 KB, type:  APP, subtype: OTA_0
               app1 : addr: 0x00150000, size:  1280.0 KB, type:  APP, subtype: OTA_1
             spiffs : addr: 0x00290000, size:  1408.0 KB, type: DATA, subtype: SPIFFS
           coredump : addr: 0x003F0000, size:    64.0 KB, type: DATA, subtype: COREDUMP
------------------------------------------
Software Info:
------------------------------------------
  Compile Date/Time : Mar 17 2025 15:30:11
  Compile Host OS   : linux
  ESP-IDF Version   : v5.3.2-282-gcfea4f7c98-dirty
  Arduino Version   : 3.1.1
------------------------------------------
Board Info:
------------------------------------------
  Arduino Board     : ESP32_WROOM_DA
  Arduino Variant   : esp32da
  Arduino FQBN      : esp32:esp32:esp32da:PartitionScheme=default,CPUFreq=240,FlashMode=qio,FlashFreq=80,FlashSize=4M,UploadSpeed=921600,LoopCore=1,EventsCore=1,DebugLevel=verbose,EraseFlash=none
============ Before Setup End ============
[   741][V][esp32-hal-uart.c:421] uartBegin(): UART0 baud(115200) Mode(800001c) rxPin(3) txPin(1)
[   750][V][esp32-hal-uart.c:510] uartBegin(): UART0 not installed. Starting installation
[   761][V][esp32-hal-uart.c:575] uartBegin(): UART0 initialization done.
[   795][V][NetworkEvents.cpp:113] _checkForEvent(): Network Event: 101 - WIFI_READY
[   955][I][WiFiGeneric.cpp:799] setDualAntennaConfig(): TX Antenna will be automatically selected
[   956][V][STA.cpp:186] _onStaEvent(): STA Started
[   968][V][NetworkEvents.cpp:113] _checkForEvent(): Network Event: 110 - STA_START
[   976][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 110 - STA_START
Connecting to WiFi ...[  1034][V][STA.cpp:206] _onStaEvent(): STA Connected: SSID: SFR_A760, BSSID: cc:2d:1b:73:a7:66, Channel: 1, Auth: WPA_WPA2_PSK
[  1046][V][NetworkEvents.cpp:113] _checkForEvent(): Network Event: 112 - STA_CONNECTED
[  1054][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 112 - STA_CONNECTED
[  1554][V][NetworkInterface.cpp:78] _onIpEvent(): sta Got New IP: 192.168.1.87 MASK: 255.255.255.0 GW: 192.168.1.1
[  1565][V][NetworkEvents.cpp:113] _checkForEvent(): Network Event: 115 - STA_GOT_IP
[  1572][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 115 - STA_GOT_IP
[  1579][V][STA.cpp:171] _onStaArduinoEvent(): STA IP: 192.168.1.87, MASK: 255.255.255.0, GW: 192.168.1.1

192.168.1.87
RRSI: -45
=========== After Setup Start ============
INTERNAL Memory Info:
------------------------------------------
  Total Size        :   336808 B ( 328.9 KB)
  Free Bytes        :   245364 B ( 239.6 KB)
  Allocated Bytes   :    81420 B (  79.5 KB)
  Minimum Free Bytes:   242896 B ( 237.2 KB)
  Largest Free Block:   110580 B ( 108.0 KB)
------------------------------------------
GPIO Info:
------------------------------------------
  GPIO : BUS_TYPE[bus/unit][chan]
  --------------------------------------  
     1 : UART_TX[0]
     3 : UART_RX[0]
============ After Setup End =============
ESP32TEMP Ok
ESP32TEMP Ok
ESP32TEMP Ok
...
8

Response given by espressif:

This is a different hostname. One that is reported to the DHCP server, not one that you can ping.

  • For Windows you needs NBNS (ping ESP32TEMP)
  • For Mac and Linux you need MDNS (ping ESP32TEMP.local)
#include "NetBIOS.h"
#include "ESPmDNS.h"
 #include <WiFi.h>

// Replace with your network credentials (STATION)
// const char* ssid = "REPLACE_WITH_YOUR_SSID";
// const char* password = "REPLACE_WITH_YOUR_PASSWORD";

String hostname = "ESP32TEMP";

void initWiFi() {
  WiFi.setHostname(hostname.c_str()); //define hostname
  
  WiFi.mode(WIFI_STA);
  
  WiFi.begin(ssid, password);
  Serial.print("Connecting to WiFi ..");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(1000);
  }
  Serial.println(WiFi.localIP());
}

void setup() {
  Serial.begin(115200);
  initWiFi();
  Serial.print("RSSI: ");
  Serial.println(WiFi.RSSI());
  NBNS.begin(hostname.c_str());
  MDNS.begin(hostname.c_str());
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(1000);
  Serial.print(WiFi.getHostname());
  Serial.println(" Ok");
}
9

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