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# mDNS example
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Shows how to use mDNS to advertise lookup services and hosts
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## Example workflow
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- mDNS is initialized with host name and instance name defined through the project configuration and `_http._tcp` service is added to be advertised
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- A delegated host `esp32-delegated._local` is added and another `_http._tcp` service is added for this host.
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- WiFi STA is started and trying to connect to the access point defined through the project configuration
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- The system event handler is used to pass the network events to mDNS so the service is aware when the interface comes up or down
- GPIO0 (BOOT Button) is initialized as pulled-up input that can be monitored for button press
- Example task is started to check if the button is pressed so it can execute the mDNS queries defined
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### Configure the project
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* Open the project configuration menu (`idf.py menuconfig` )
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* Configure Wi-Fi or Ethernet under "Example Connection Configuration" menu
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* Set `mDNS Hostname` as host name prefix for the device and its instance name in `mDNS Instance Name`
* Disable `Resolve test services` to prevent the example from querying defined names/services on startup (cause warnings in example logs, as illustrated below)
### Build and Flash
Build the project and flash it to the board, then run monitor tool to view serial output:
```
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idf.py -p PORT flash monitor
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```
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- Wait for WiFi to connect to your access point
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- You can now ping the device at `[board-hostname].local` , where `[board-hostname]` is preconfigured hostname, `esp32-mdns` by default.
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- You can also browse for `_http._tcp` on the same network to find the advertised service
- Pressing the BOOT button will start querying the local network for the predefined in `check_button` hosts and services
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- Note that for purpose of CI tests, configuration options of `MDNS_RESOLVE_TEST_SERVICES` and `MDNS_ADD_MAC_TO_HOSTNAME` are available, but disabled by default. If enabled, then the hostname suffix of last 3 bytes from device MAC address is added, e.g. `esp32-mdns-80FFFF` , and a query for test service is issued.
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(To exit the serial monitor, type ``Ctrl-]` `.)
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
## Example Output
```
I (0) cpu_start: Starting scheduler on APP CPU.
I (276) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
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I (276) mdns-test: mdns hostname set to: [esp32-mdns]
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I (286) wifi: wifi driver task: 3ffc2fa4, prio:23, stack:3584, core=0
I (286) wifi: wifi firmware version: a3be639
I (286) wifi: config NVS flash: enabled
I (296) wifi: config nano formating: disabled
I (296) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (306) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (336) wifi: Init dynamic tx buffer num: 32
I (336) wifi: Init data frame dynamic rx buffer num: 32
I (336) wifi: Init management frame dynamic rx buffer num: 32
I (346) wifi: Init static rx buffer size: 1600
I (346) wifi: Init static rx buffer num: 10
I (346) wifi: Init dynamic rx buffer num: 32
I (356) mdns-test: Setting WiFi configuration SSID myssid...
I (426) phy: phy_version: 4000, b6198fa, Sep 3 2018, 15:11:06, 0, 0
I (426) wifi: mode : sta (30:ae:a4:80:FF:FF)
I (426) gpio: GPIO[0]| InputEn: 1| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (1756) wifi: n:11 0, o:1 0, ap:255 255, sta:11 0, prof:1
I (2736) wifi: state: init -> auth (b0)
I (2756) wifi: state: auth -> assoc (0)
I (2766) wifi: state: assoc -> run (10)
I (2786) wifi: connected with myssid, channel 11
I (2786) wifi: pm start, type: 1
I (4786) event: sta ip: 192.168.0.139, mask: 255.255.255.0, gw: 192.168.0.2
I (21126) mdns-test: Query A: esp32.local
W (23176) mdns-test: ESP_ERR_NOT_FOUND: Host was not found!
I (23176) mdns-test: Query PTR: _arduino._tcp.local
W (26276) mdns-test: No results found!
I (26276) mdns-test: Query PTR: _http._tcp.local
1: Interface: STA, Type: V6
PTR : HP Color LaserJet MFP M277dw (7C2E10)
SRV : NPI7C2E10.local:80
A : 254.128.0.0
2: Interface: STA, Type: V4
PTR : switch4e4919
SRV : switch4e4919.local:80
TXT : [1] path=/config/authentication_page.htm;
A : 192.168.0.118
I (29396) mdns-test: Query PTR: _printer._tcp.local
1: Interface: STA, Type: V6
PTR : HP Color LaserJet MFP M277dw (7C2E10)
SRV : NPI7C2E10.local:515
A : 254.128.0.0
2: Interface: STA, Type: V4
PTR : HP Color LaserJet MFP M277dw (7C2E10)
```
