Shop Esp32 Relay Control

Sponsored
About our ads
$18.99
AC/DC Power Supply ESP32 Development Board Programmable Development Board Wireless Wifi 8 Way Channel 5V Relay Module ESP32-WROOM-32E For Arduino
Amazon.com
11
$18.99
AC/DC Power Supply ESP32 Development Board Programmable Development Board Wireless Wifi 8 Way Channel 5V Relay Module ESP32-WROOM-32E For Arduino
Amazon.com
11
$23.99
$29.99
ESP32 WLED LED Strip Light Controller 15A Fuse Link Built In Mic UART Type-C Energy Saving Relay App Control Wago Wiring For RGB IC Addressable
Amazon.com
31
20% off
$23.99
$29.99
ESP32 WLED LED Strip Light Controller 15A Fuse Link Built In Mic UART Type-C Energy Saving Relay App Control Wago Wiring For RGB IC Addressable
Amazon.com
31
$4.39
$5.17
ESP32-32E MOS Switch Relay Module 5-80V Input Development Board Power Supply Accessories
Aliexpress
15% off
$4.39
$5.17
ESP32-32E MOS Switch Relay Module 5-80V Input Development Board Power Supply Accessories
Aliexpress
$18.00
Wired DC-DC 10Amp Isolated Solid State Relay Module, SSR In 3-32VDC Out 5-30VDC, For Raspberry-Pi Arduino ESP32 PLC MCU DSP
Amazon.com
53
$18.00
Wired DC-DC 10Amp Isolated Solid State Relay Module, SSR In 3-32VDC Out 5-30VDC, For Raspberry-Pi Arduino ESP32 PLC MCU DSP
Amazon.com
53
$55.00
$500.00
Esphome Home Assistant ESP32 Relay Switch Board A16 MQTT TCP Web HTTP Tuya Tasmota Arduino IDE
Aliexpress
Free shipping
89% off
$55.00
$500.00
Esphome Home Assistant ESP32 Relay Switch Board A16 MQTT TCP Web HTTP Tuya Tasmota Arduino IDE
Aliexpress
Free shipping
$4.78
$6.42
DC 5-60V ESP32 2/4-Way MOS Switch Module Single-Way Relay Module ESP32-32E Module WIFI Bluetooth
Aliexpress
25% off
$4.78
$6.42
DC 5-60V ESP32 2/4-Way MOS Switch Module Single-Way Relay Module ESP32-32E Module WIFI Bluetooth
Aliexpress
$31.47
$64.27
16 Channel Relay Module Board For ESP32-WROOM Relay Development Board For Smart Home DC5-12V
Aliexpress
Free shipping
51% off
$31.47
$64.27
16 Channel Relay Module Board For ESP32-WROOM Relay Development Board For Smart Home DC5-12V
Aliexpress
Free shipping
$8.55
$17.67
1/2/4/8 Channel ESP32 Wifi Bluetooth-Compatible Relay Module AC90-250V DC5-30V Smart Home Automation
Aliexpress
Free shipping
51% off
$8.55
$17.67
1/2/4/8 Channel ESP32 Wifi Bluetooth-Compatible Relay Module AC90-250V DC5-30V Smart Home Automation
Aliexpress
Free shipping
$10.71
$22.33
ESP32 WIFI Bluetooth-Compatible Relay Module - 1/2/4/8 Channels, AC90-250V/DC5-30V - ESP32-WROOM
Aliexpress
Free shipping
52% off
$10.71
$22.33
ESP32 WIFI Bluetooth-Compatible Relay Module - 1/2/4/8 Channels, AC90-250V/DC5-30V - ESP32-WROOM
Aliexpress
Free shipping
$6.21
$20.69
AC 220V Relay Module ESP32 WIFI Bluetooth AC-DC Dual Relay Switch Control Power Supply ESP32
Aliexpress
Free shipping
69% off
$6.21
$20.69
AC 220V Relay Module ESP32 WIFI Bluetooth AC-DC Dual Relay Switch Control Power Supply ESP32
Aliexpress
Free shipping
$494.70
8 Channel Relay Module ESP32 Wifi Wireless Control BLE Development Board ESP32-WROOM-32E DC 530V(8 Channels)
zithazi
$494.70
8 Channel Relay Module ESP32 Wifi Wireless Control BLE Development Board ESP32-WROOM-32E DC 530V(8 Channels)
zithazi
$6.34
$10.29
ESP32 5V 12V Relay Board Dual Channel Wireless WIFI Relay Module ESP32 Development Board DC5-60V For
Aliexpress
38% off
$6.34
$10.29
ESP32 5V 12V Relay Board Dual Channel Wireless WIFI Relay Module ESP32 Development Board DC5-60V For
Aliexpress
$8.29
$13.41
ESP32 4 Way Relay Module AC 220V 30A ESP32E Module Onboard Supports Development Wi-Fi Bluetooth 4
Aliexpress
38% off
$8.29
$13.41
ESP32 4 Way Relay Module AC 220V 30A ESP32E Module Onboard Supports Development Wi-Fi Bluetooth 4
Aliexpress
$15.28
$56.61
ESP32-S3-RS485-CAN 1-Channel Wifi Bluetooth Relay ESP32 Control Development Board RS485 CAN
Aliexpress
Free shipping
73% off
$15.28
$56.61
ESP32-S3-RS485-CAN 1-Channel Wifi Bluetooth Relay ESP32 Control Development Board RS485 CAN
Aliexpress
Free shipping
$24.56
$24.62
DC 7-24V ESP32 C3 Super Mini Expansion Board 4AI-4DO RS485 Relay Module For Arduino WEB MQTT
Aliexpress
Free shipping
$24.56
$24.62
DC 7-24V ESP32 C3 Super Mini Expansion Board 4AI-4DO RS485 Relay Module For Arduino WEB MQTT
Aliexpress
Free shipping
$9.51
$11.89
WIFI Bluetooth 4-Channel 30A Relay Module Development Board ESP32 Secondary Development AC 220V
Aliexpress
20% off
$9.51
$11.89
WIFI Bluetooth 4-Channel 30A Relay Module Development Board ESP32 Secondary Development AC 220V
Aliexpress
$12.97
$17.29
30A ESP32-WROOM-32E Development Board Relay Module DC7-28/5V 1-Channel WIFI Relay Module For Smart
Aliexpress
Free shipping
24% off
$12.97
$17.29
30A ESP32-WROOM-32E Development Board Relay Module DC7-28/5V 1-Channel WIFI Relay Module For Smart
Aliexpress
Free shipping
$10.69
$32.75
ESP32 1/2/8 Channel Power Supply Module DC 5-30/60V WIFI Bluetooth-Compatible BLE Relay Module
Aliexpress
Free shipping
67% off
$10.69
$32.75
ESP32 1/2/8 Channel Power Supply Module DC 5-30/60V WIFI Bluetooth-Compatible BLE Relay Module
Aliexpress
Free shipping
$7.07
$14.13
AC 220V 30A WIFI BT 4 Way Relay Module Onboard Esp32e ESP32 ESP8266 Module Supports Secondary
Aliexpress
49% off
$7.07
$14.13
AC 220V 30A WIFI BT 4 Way Relay Module Onboard Esp32e ESP32 ESP8266 Module Supports Secondary
Aliexpress
$16.25
AC 90-250V/DC 7-12V Power Supply WIFI Bluetooth BLE 1 Channel Relay Module ESP32-C3/ESP-C3-12F
Aliexpress
Free shipping
$16.25
AC 90-250V/DC 7-12V Power Supply WIFI Bluetooth BLE 1 Channel Relay Module ESP32-C3/ESP-C3-12F
Aliexpress
Free shipping
$30.15
Bevrlink 8 Channel Relay V1 24V Compatible With Arduino, Raspberry Pi, Rock, ESP32, ESP8266 And Other Sbcs And Microcontrollers - I2C GPIO (SBC, Case,
Amazon.com
$30.15
Bevrlink 8 Channel Relay V1 24V Compatible With Arduino, Raspberry Pi, Rock, ESP32, ESP8266 And Other Sbcs And Microcontrollers - I2C GPIO (SBC, Case,
Amazon.com
$12.54
$15.29
ESP32 Single-Channel AC220V Power Supply 30A WIFI Relay Module Development Board Support UART
Aliexpress
Free shipping
17% off
$12.54
$15.29
ESP32 Single-Channel AC220V Power Supply 30A WIFI Relay Module Development Board Support UART
Aliexpress
Free shipping
$8.51
$17.03
AC90-250V ESP32 Wifi Bluetooth Single Relay Switch Module Board ESP32 Development Board 4m Byte
Aliexpress
50% off
$8.51
$17.03
AC90-250V ESP32 Wifi Bluetooth Single Relay Switch Module Board ESP32 Development Board 4m Byte
Aliexpress
$30.54
$60.51
DC5V/12V/24V Power Supply ESP32 16 Channel Relay Module Development Board ESP32-WROOM Secondary
Aliexpress
Free shipping
49% off
$30.54
$60.51
DC5V/12V/24V Power Supply ESP32 16 Channel Relay Module Development Board ESP32-WROOM Secondary
Aliexpress
Free shipping
$32.19
$33.42
DC 12V 24V 8CH Wifi Relay 30Pin ESP32 Programmable Expansion Board Modbus RS485 IO Module For
Aliexpress
Free shipping
$32.19
$33.42
DC 12V 24V 8CH Wifi Relay 30Pin ESP32 Programmable Expansion Board Modbus RS485 IO Module For
Aliexpress
Free shipping
$24.69
GLEDOPTO ESP32 WLED Controller DC 5V-24V IP65 Waterproof Dynamic RGB IC Lighting DIY Outdoor Lighting Wifi APP Control For WS2811 WS2812 SK6812 TM1814
Amazon.com
18
$24.69
GLEDOPTO ESP32 WLED Controller DC 5V-24V IP65 Waterproof Dynamic RGB IC Lighting DIY Outdoor Lighting Wifi APP Control For WS2811 WS2812 SK6812 TM1814
Amazon.com
18
$17.38
$23.81
4 Channel Relay Module 30A DC7-28/5V WIFI Bluetooth Relay Module ESP32-WROOM Development Board
Aliexpress
27% off
$17.38
$23.81
4 Channel Relay Module 30A DC7-28/5V WIFI Bluetooth Relay Module ESP32-WROOM Development Board
Aliexpress
$8.86
$17.21
ESP32 WIFI Bluetooth-Compatible BLE Relay Module 1/2/8 Channel ESP32-Development Board ESP32 WIFI BT
Aliexpress
Free shipping
48% off
$8.86
$17.21
ESP32 WIFI Bluetooth-Compatible BLE Relay Module 1/2/8 Channel ESP32-Development Board ESP32 WIFI BT
Aliexpress
Free shipping
$27.36
$28.33
DC 12V 24V ESP32 Expansion Board Digital Analog DAC ADC IO Wifi Relay Switch ES32C14 Module For
Aliexpress
Free shipping
$27.36
$28.33
DC 12V 24V ESP32 Expansion Board Digital Analog DAC ADC IO Wifi Relay Switch ES32C14 Module For
Aliexpress
Free shipping
$6.65
$8.25
AC220V Power Supply ESP32 WIFI Bluetooth-Compatible 2 Channel Relay Module ESP32 Development Board
Aliexpress
19% off
$6.65
$8.25
AC220V Power Supply ESP32 WIFI Bluetooth-Compatible 2 Channel Relay Module ESP32 Development Board
Aliexpress
$34.61
$72.11
LILYGO T-Relays3 ESP32-S3 6-Way Relay Development Board ABS Expansion Board LCD Display
Aliexpress
52% off
$34.61
$72.11
LILYGO T-Relays3 ESP32-S3 6-Way Relay Development Board ABS Expansion Board LCD Display
Aliexpress
$7.32
1/2/4/8 Channel ESP32 WIFI Bluetooth-Compatible BLE Relay Module AC90-250V/DC5-30V Power Supply
Aliexpress
$7.32
1/2/4/8 Channel ESP32 WIFI Bluetooth-Compatible BLE Relay Module AC90-250V/DC5-30V Power Supply
Aliexpress
$4.94
$13.73
ESP32 Relay Development Board AC/DC Power Supply Voltage Monitor Wifi Bluetooth BLE 4 Channel
Aliexpress
Free shipping
64% off
$4.94
$13.73
ESP32 Relay Development Board AC/DC Power Supply Voltage Monitor Wifi Bluetooth BLE 4 Channel
Aliexpress
Free shipping
$12.10
$16.80
AC / DC Power Supply ESP32 Wifi BT Ble 4 Channel Relay Module ESP32-WROOM Development Board
Aliexpress
27% off
$12.10
$16.80
AC / DC Power Supply ESP32 Wifi BT Ble 4 Channel Relay Module ESP32-WROOM Development Board
Aliexpress
$224.00
$280.00
KC868-A32 ESP32 Development Board MQTT HTTP Esphome Home Assistant Tasmota Wifi Relay Switch Arduino
Aliexpress
Free shipping
20% off
$224.00
$280.00
KC868-A32 ESP32 Development Board MQTT HTTP Esphome Home Assistant Tasmota Wifi Relay Switch Arduino
Aliexpress
Free shipping
$16.37
$33.17
ESP32 WIFI Bluetooth BLE Quad Relay Module ESP32-WROOM Development Board AC220V/DC5-30V Power Supply
Aliexpress
Free shipping
50% off
$16.37
$33.17
ESP32 WIFI Bluetooth BLE Quad Relay Module ESP32-WROOM Development Board AC220V/DC5-30V Power Supply
Aliexpress
Free shipping
ESP32 Relay Module - Control AC Appliances (Web Server) | Random Nerd Tutorials
ESP32 Relay Module - Control AC Appliances (Web Server) | Rando…
Dec 18, 2019
randomnerdtutorials.com
ESP32 Web Server to Control 220V Lamp Remotely
ESP32 Web Server to Control 220V Lamp Remotely
Jul 26, 2023
microcontrollerslab.com
How to Control a Relay Module With an ESP32
5:01
How to Control a Relay Module With an ESP32
40.4K viewsSep 4, 2018
YouTubeMaker Pro
Home Automation System using ESP32 with Blynk IR remote & Manual control Relay | IoT Projects 2021
9:19
Home Automation System using ESP32 with Blynk IR remote & Ma…
53.3K viewsMay 9, 2021
YouTubeTech StudyCell
ESP32 Arduino HTTP server: controlling a relay remotely
ESP32 Arduino HTTP server: controlling a relay remotely
Mar 2, 2018
techtutorialsx.com
IoT Smart Home project using ESP32 Blynk control relay with WiFi + Manual Switch - 2021
11:05
IoT Smart Home project using ESP32 Blynk control relay with Wi…
51.1K viewsNov 6, 2021
YouTubeTech StudyCell
Web-Based Relay Control System Using ESP32 | IoT Home Automation
4:10
Web-Based Relay Control System Using ESP32 | IoT Home Automation
820 viewsFeb 2, 2025
YouTubeRoboXpert
10:18
Home Automation using ESP32 Bluetooth and IR remote control R…
34.8K viewsJul 31, 2021
YouTubeTech StudyCell
2:28
ESP32 tutorial A-11: The relay
6.9K viewsApr 9, 2018
YouTubeADEL KASSAH
10:19
ESP-NOW Project: ESP32 Master-Slave Relay Control + OLED Feed…
13.2K views9 months ago
YouTubeTech StudyCell
10:59
Home Automation Made Easy: ESP32 and 4-Channel Relay Modul…
2.3K viewsApr 21, 2023
YouTubeHouseWiresTV
18:12
Control a Relay with ESP32 via Bluetooth Using MIT App Inventor…
384 views11 months ago
YouTubeIOT Station
9:47
Smart Home Automation using Blynk & ESP32 IoT projects | WiFi …
81.2K viewsDec 29, 2020
YouTubeTech StudyCell
21:58
ESP32 Getting started | Control Relays using ESP32 Wi-Fi webser…
8.2K viewsFeb 4, 2021
YouTubehash include electronics
4:51
Controlling Relay Board (ESP32 + Arduino Series)
39K viewsMay 22, 2020
YouTubeSimply Explained
6:23
simulation of esp32 controlling with relay | Simulation of esp32 with rel…
5.7K viewsApr 30, 2023
YouTubeNelson Darwin Pak Tech
7:22
Tech Note 149 - ESP32 4-Channel Relay / GPIO Controller with Web UI
9.9K viewsJan 10, 2021
YouTubeG6EJD - David
7:49
Make simple ESP32 Home Automation project | Web UI + EE…
14.2K views8 months ago
YouTubeTech StudyCell
23:42
ESP32 Project: How to control 2 AC bulb or load using 2 Relay over Wi…
4.4K viewsFeb 29, 2020
YouTubeRobojax
51:59
Arduino IoT Cloud 2021 - Getting Started with Arduino & ESP32
418.2K viewsAug 1, 2021
YouTubeDroneBot Workshop
10:32
ESP32 RTC DS3231 control Relay with OLED clock | Set time with E…
16.9K viewsApr 30, 2024
YouTubeTech StudyCell
7:37
ESP32 #1 Build an Web Server with ESP32 to control Relay | ESP32 pr…
1.7K views5 months ago
YouTubeBenedict's Lab
6:17
Arduino IOT Cloud with ESP32 Relay Control
9.3K viewsSep 10, 2021
YouTubeAhmad Logs
5:59
How to use a RELAY with ESP32 | Easy Guide
92.6K viewsAug 28, 2023
YouTubeINOVATRIX
11:39
Home Automation using ESP32 Bluetooth control relay //ESP32 Sa…
17K viewsMay 23, 2022
YouTubeArup Experiment
0:15
ESP32 Arduino: controlling a relay demo [written tutorial in blog]
6.4K viewsFeb 17, 2018
YouTubeTechtutorialsx
4:13
ESP32 IR Remote Controlled 4-Relay System with EEPROM | Save Stat…
1.3K views7 months ago
YouTubeRoboXpert
10:54
IoT ESP32: Control DC Motor over WiFi using 2 channel relay - RJT279
13.6K viewsMar 7, 2020
YouTubeRobojax
0:22
ESP32 WiFi Relay Control ⚡
1.2K views4 months ago
YouTubeNextCraft
See more videos
Static thumbnail place holder

Shop Esp32 Relay Control

Sponsored
About our ads
$18.99
AC/DC Power Supply ESP32 Development Board Programmable Development Board Wireless Wifi 8 Way Channel 5V Relay Module ESP32-WROOM-32E For Arduino
Amazon.com
11
$18.99
AC/DC Power Supply ESP32 Development Board Programmable Development Board Wireless Wifi 8 Way Channel 5V Relay Module ESP32-WROOM-32E For Arduino
Amazon.com
11
$23.99
$29.99
ESP32 WLED LED Strip Light Controller 15A Fuse Link Built In Mic UART Type-C Energy Saving Relay App Control Wago Wiring For RGB IC Addressable
Amazon.com
31
20% off
$23.99
$29.99
ESP32 WLED LED Strip Light Controller 15A Fuse Link Built In Mic UART Type-C Energy Saving Relay App Control Wago Wiring For RGB IC Addressable
Amazon.com
31
$4.39
$5.17
ESP32-32E MOS Switch Relay Module 5-80V Input Development Board Power Supply Accessories
Aliexpress
15% off
$4.39
$5.17
ESP32-32E MOS Switch Relay Module 5-80V Input Development Board Power Supply Accessories
Aliexpress
$18.00
Wired DC-DC 10Amp Isolated Solid State Relay Module, SSR In 3-32VDC Out 5-30VDC, For Raspberry-Pi Arduino ESP32 PLC MCU DSP
Amazon.com
53
$18.00
Wired DC-DC 10Amp Isolated Solid State Relay Module, SSR In 3-32VDC Out 5-30VDC, For Raspberry-Pi Arduino ESP32 PLC MCU DSP
Amazon.com
53
$55.00
$500.00
Esphome Home Assistant ESP32 Relay Switch Board A16 MQTT TCP Web HTTP Tuya Tasmota Arduino IDE
Aliexpress
Free shipping
89% off
$55.00
$500.00
Esphome Home Assistant ESP32 Relay Switch Board A16 MQTT TCP Web HTTP Tuya Tasmota Arduino IDE
Aliexpress
Free shipping
$4.78
$6.42
DC 5-60V ESP32 2/4-Way MOS Switch Module Single-Way Relay Module ESP32-32E Module WIFI Bluetooth
Aliexpress
25% off
$4.78
$6.42
DC 5-60V ESP32 2/4-Way MOS Switch Module Single-Way Relay Module ESP32-32E Module WIFI Bluetooth
Aliexpress
$31.47
$64.27
16 Channel Relay Module Board For ESP32-WROOM Relay Development Board For Smart Home DC5-12V
Aliexpress
Free shipping
51% off
$31.47
$64.27
16 Channel Relay Module Board For ESP32-WROOM Relay Development Board For Smart Home DC5-12V
Aliexpress
Free shipping
$8.55
$17.67
1/2/4/8 Channel ESP32 Wifi Bluetooth-Compatible Relay Module AC90-250V DC5-30V Smart Home Automation
Aliexpress
Free shipping
51% off
$8.55
$17.67
1/2/4/8 Channel ESP32 Wifi Bluetooth-Compatible Relay Module AC90-250V DC5-30V Smart Home Automation
Aliexpress
Free shipping
$10.71
$22.33
ESP32 WIFI Bluetooth-Compatible Relay Module - 1/2/4/8 Channels, AC90-250V/DC5-30V - ESP32-WROOM
Aliexpress
Free shipping
52% off
$10.71
$22.33
ESP32 WIFI Bluetooth-Compatible Relay Module - 1/2/4/8 Channels, AC90-250V/DC5-30V - ESP32-WROOM
Aliexpress
Free shipping
$6.21
$20.69
AC 220V Relay Module ESP32 WIFI Bluetooth AC-DC Dual Relay Switch Control Power Supply ESP32
Aliexpress
Free shipping
69% off
$6.21
$20.69
AC 220V Relay Module ESP32 WIFI Bluetooth AC-DC Dual Relay Switch Control Power Supply ESP32
Aliexpress
Free shipping
$494.70
8 Channel Relay Module ESP32 Wifi Wireless Control BLE Development Board ESP32-WROOM-32E DC 530V(8 Channels)
zithazi
$494.70
8 Channel Relay Module ESP32 Wifi Wireless Control BLE Development Board ESP32-WROOM-32E DC 530V(8 Channels)
zithazi
$6.34
$10.29
ESP32 5V 12V Relay Board Dual Channel Wireless WIFI Relay Module ESP32 Development Board DC5-60V For
Aliexpress
38% off
$6.34
$10.29
ESP32 5V 12V Relay Board Dual Channel Wireless WIFI Relay Module ESP32 Development Board DC5-60V For
Aliexpress
$8.29
$13.41
ESP32 4 Way Relay Module AC 220V 30A ESP32E Module Onboard Supports Development Wi-Fi Bluetooth 4
Aliexpress
38% off
$8.29
$13.41
ESP32 4 Way Relay Module AC 220V 30A ESP32E Module Onboard Supports Development Wi-Fi Bluetooth 4
Aliexpress
$15.28
$56.61
ESP32-S3-RS485-CAN 1-Channel Wifi Bluetooth Relay ESP32 Control Development Board RS485 CAN
Aliexpress
Free shipping
73% off
$15.28
$56.61
ESP32-S3-RS485-CAN 1-Channel Wifi Bluetooth Relay ESP32 Control Development Board RS485 CAN
Aliexpress
Free shipping
$24.56
$24.62
DC 7-24V ESP32 C3 Super Mini Expansion Board 4AI-4DO RS485 Relay Module For Arduino WEB MQTT
Aliexpress
Free shipping
$24.56
$24.62
DC 7-24V ESP32 C3 Super Mini Expansion Board 4AI-4DO RS485 Relay Module For Arduino WEB MQTT
Aliexpress
Free shipping
$9.51
$11.89
WIFI Bluetooth 4-Channel 30A Relay Module Development Board ESP32 Secondary Development AC 220V
Aliexpress
20% off
$9.51
$11.89
WIFI Bluetooth 4-Channel 30A Relay Module Development Board ESP32 Secondary Development AC 220V
Aliexpress
$12.97
$17.29
30A ESP32-WROOM-32E Development Board Relay Module DC7-28/5V 1-Channel WIFI Relay Module For Smart
Aliexpress
Free shipping
24% off
$12.97
$17.29
30A ESP32-WROOM-32E Development Board Relay Module DC7-28/5V 1-Channel WIFI Relay Module For Smart
Aliexpress
Free shipping
$10.69
$32.75
ESP32 1/2/8 Channel Power Supply Module DC 5-30/60V WIFI Bluetooth-Compatible BLE Relay Module
Aliexpress
Free shipping
67% off
$10.69
$32.75
ESP32 1/2/8 Channel Power Supply Module DC 5-30/60V WIFI Bluetooth-Compatible BLE Relay Module
Aliexpress
Free shipping