@mfalkvidd
Actually he did but under Hssio the "sudo" keyword is not acknowledged. Tried without this 'super user do' keyword but nothing

Today, when I connected the arduino through the usb port in the raspberry pi 3, then entered the /dev directory, I saw this :

Isn't that weird ? what is the "p" is doing there between the tty and the USB0 ? also tried accessing this "ttypUSB0" but still get an error

@gohan OK I see . I'll try it today. Thanks

@gohan this : link text.
I know how to connect the nrf to the arduino board but I don't know how to connect the esp8266-12 with the nrf and the arduino (it does not explained in the link).

@gohan I thought that the esp8266 may be just a replacement to the WizNET (W5100) or the ENC28J60 (suggested in the mysensors instructions to built Ethernet / MQTT gateways). But from what I understand, upon your link you gave me, I don't see the nrf24 module connected to the ESP8266-12 , but the ESP8266-12 module solely.

Note that I need the nrf24 to be a part of the Ethernet gateway in order to be able to communicate with the nodes

Sorry to hear that.
I think the .img file is the same but I'm not 100% sure.

@mntlvr
BTW, you can find all the hassio versions here :
link text

The latest release is 0.67.1 ...

Mine is RPI3
I don't think that it has a relation to your internet.
Try flashing the SD card again by following these instructions :
link text

@gohan Actually I have the ESP8266-12 and I'll give it a try also (at the same time, ordered the WizNET (W5100) Ethernet module and the ENC28J60 Ethernet module but it will take time until I'll get it) , just wanted to solve the problem with the serial gateway ...

@mntlvr you can google "hass.io" released versions for example...
I have no problem with v0.67 (upgraded) so maybe something in the flashing went wrong, try to flash it again with the "etcher" and update us about the status