I used platformio IDE

I did "platformio lib install 1101"
(<http://platformio.org/lib/show/1101/ESP8266wifi>),

I installed this: <http://platformio.org/lib/show/549/WebSockets> (follow instructions)

I did similar things to other libraries.

When I click the platformio:build button, it still complains:

> 
> fatal error: ESP8266WiFi.h: No such file or directory fatal error:
> 
> 
> ESP8266WiFiMulti.h: No such file or directory fatal error:
> 
> 
> ESP8266Webserver.h: No such file or directory
> 
> 
>
['https://arduino.stackexchange.com/questions/23809', 'https://arduino.stackexchange.com', 'https://arduino.stackexchange.com/users/20742/']
While Bhushan Patil's answer should work, it would still make future projects tedious. Instead you can add the header files to the hardware library, and use them at will, with the `#include <library>` syntax every other library uses in C/C++.

The PlatformIO IDE has a config file you can modify that tells the IDE where to look for libraries. You could read this file, and determine where to put your header files, such that PlatformIO could find them, or add a location to look for header files in. See this page from the PlatformIO documentation:  

<http://docs.platformio.org/en/latest/projectconf.html>

Beyond that, you could also use the absolute path for the header file (library) you are trying to use, by doing something like

```
#include "/home/user/path/to/user/library.h"

```
Make sure **ESP8266WiFi.h**, **ESP8266WiFiMulti.h**, **ESP8266Webserver.h** files are located in the same directory where your \*.uno file present.