How to get the IP address of a node by its mdns host name in Arduino ESP32

1. Introduction
- The benefit of mDNS is mentioned here.

- This is necessary when our ESP32 want to connect to a gateway/server (node) without knowing its IP address except the mdns host name.
- We will use the function "IPAddress queryHost(char *host)" which is available in the mdns library.
- In order to use this function, our Arduino ESP32 must join in the same network with the node and mdns service is initialized on ESP32.
2. Hardware
No extra hardware
3. Software

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#include <WiFi.h> #include <ESPmDNS.h> #include <WiFiClient.h> const char* ssid = "dd-wrt"; const char* password = "0000000000"; char * serverHostname = "iotsharing";//only use host name and remove .local void setup(void) { Serial.begin(115200); // Connect to WiFi network WiFi.begin(ssid, password); Serial.println(""); // Wait for connection while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(""); Serial.print("Connected to "); Serial.println(ssid); Serial.print("IP address: "); Serial.println(WiFi.localIP()); if (!MDNS.begin("esp32")) { Serial.println("Error setting up MDNS responder!"); while(1) { delay(1000); } } Serial.println("mDNS responder started"); IPAddress serverIp = MDNS.queryHost(serverHostname); Serial.print("IP address of server: "); Serial.println(serverIp.toString()); } void loop(void) { }

4. Result

Figure: Host name to IP