ESP8266 tutorial 1- introduction of esp8266(esp12e) Wifi module for IoT

Wireless network is essential for IoT device, so we should choose one of the wireless network solution among WiFi, Bluetooth or any others.
The most popular wireless networks are WiFi and BLE and there's pros and cons.
Bluetooth BLE is best for power consumption but it need BLE gateway to communicate through internet. If you are not familiar with BLE gateway, please see following product information.

BEL gateway product, iGS01.
Product information : ingics.com homepage

BLE gateway (from ingics.com homepage)

I think you don't have BLE gateway in your home work workplace because it's not common device. so I think it is the one of the disadvantage of BLE network for IoT.

WiFi network is very common and we can easily find WiFi AP at home or work place. so low power WiFi is better than BLE for simple IoT network. The low cost and low power WiFi module for IoT is ESP8266 module.

There are many types of ESP8266 module and you can choose one of them according to your IoT device spec. you can find all kind of ESP8266 module in following website. As far as I know, esp12e is popular now and you can buy it through internet very easily.

ESP8266 module - following table is from this web page.

Board ID	pins	pitch	form factor	LEDs	Antenna	Ant.Socket	Shielded	dimensions mm
ESP-01	8	.1“	2×4 DIL	Yes	Etched-on PCB	No	No	14.3 x 24.8
ESP-02	8	.1”	2×4 notch	No?	None	Yes	No	14.2 x 14.2
ESP-03	14	2mm	2×7 notch	No	Ceramic	No	No	17.3 x 12.1
ESP-04	14	2mm	2×4 notch	No?	None	No	No	14.7 x 12.1
ESP-05	5	.1“	1×5 SIL	No	None	Yes	No	14.2 x 14.2
ESP-06	12+GND	misc	4×3 dice	No	None	No	Yes	?
ESP-07	16	2mm	2×8 pinhole	Yes	Ceramic	Yes	Yes	20.0 x 16.0
ESP-08	14	2mm	2×7 notch	No	None	No	Yes	17.0 x 16.0
ESP-08 New	16	2mm	2×8 notch	No	None	No	Yes	18.0 x 16.0
ESP-09	12+GND	misc	4×3 dice	No	None	No	No	10.0 x 10.0
ESP-10	5	2mmm?	1×5 notch	No	None	No	No	14.2 x 10.0
ESP-11	8	1.27mm	1×8 pinhole	No?	Ceramic	No	No	17.3 x 12.1
ESP-12	16	2mm	2×8 notch	Yes	Etched-on PCB	No	Yes	24.0 x 16.0
ESP-12-E	22	2mm	2×8 notch	Yes	Etched-on PCB	No	Yes	24.0 x 16.0
ESP-13	18	1.5mm	2×9	?	Etched-on PCB	No	Yes	? x ?
ESP-14	22	2mm	2×8 + 6	1	Etched-on PCB	No	Yes	24.3 x 16.2
WROOM-02	18	1.5mm	2×9	No	Etched on PCB	No	Yes	20.0 x 18.0
WT8266-S1	18	1.5mm	3×6	1	Etched on PCB	No	Yes	15.0 x 18.6