I’m a great fan of the ESP8266. It’s a great little Arduino chip with WiFi built in. I’m only using the ESP-01 at the moment with just two GPIO ports, but that’s enough for a temperature sensor using MQTT to ping data back over the network.
To programme the ESP8266 I used my Arduino Uno (which is not recommended as the ESP is only suited to 3.3v, not 5v).
To programme it connect the following lines:
vcc –> 3.3v
vcc –> CH_PD
gnd –> gnd
gnd –> GPIO0
tx –> tx
rx –> rx