InternetAccess < IoT_Course

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---+ Internet access

Once we have collected data from the sensors, we want to get access to them. This can be accomplished most easily by transferring the data over the Internet. Most of the time we want to plot the data in some form or another. Often it is also desired to see real-time data.
---++ !WiFi

The !WeMos D1 mini ESP32 CPU board offers !WiFi access implementing a TCP/IP and full 802.11 b/g/n Wi-Fi MAC protocol (see the [[https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf][ESP32 datasheet]]) and the ESP32 port of !MicroPython offers a [[https://docs.micropython.org/en/latest/esp32/quickref.html#networking][ _network module_ ]] with the necessary access functions.

Before looking into the WEB server, we must first make sure we have Internet access through !WiFi.The following screen dump shows an interactive !MicroPython session where !WiFi access is granted:

<img alt="wifi_connect.jpg" height="463" src="%ATTACHURL%/wifi_connect.jpg" title="wifi_connect.jpg" width="911" />

All you need to do is putting in the correct ssid for your !WiFi network and the corresponding password. Of course you do not want to type all this each time you connect to your network and for this reason a <i>wifi_connect.py </i>module is already included in your !MicroPython binary.

%ATTACHURL%/wifi_connect_public.py.txt

provides all necessary functions to do this. It first connects to !WiFi as a station interface and prints the IP address it is connected to. If it is already connected it simply returns. Once connected it gets the current time from the NTP time server and sets up the ESP32 real time clock. You can get the current GMT time with _gmtTime()_ or CET time with _cetTime()_. The module is already included in the !MicroPython binary.

<img alt="wifi_connect.png" height="273" src="%ATTACHURL%/wifi_connect.png" title="wifi_connect.png" width="750" />

You can also get the current date and time in a more readable format with <i>dateString(currentTime), </i>where currentTime is the tuple returned by _gmtTime()_ or _cetTime()_

<img alt="dateString.png" height="203" src="%ATTACHURL%/dateString.png" title="dateString.png" width="584" />

Since I cannot know the SSID and password of your !WiFi network, <i>connect() </i>will only work for my private network. You can however pass your SSID and password as parameters:<br />connect(ssid="YourSSID",password="YourWiFiPasswword",hostname="yourHost")

You get the IP address allocate with

_getIPAddress()._

Since we have defined the hostname with:

<img alt="hostname.png" height="123" src="%ATTACHURL%/hostname.png" title="hostname.png" width="826" />

and this hostname is made known to your DNS server through mDNS, you can also address the ESP32 under its hostname: yourHost.local
---++ An FTP server

When collecting data it may be interesting to transfer them for analysis to a PC. For this an FTP server is very helpful and there is one included in the !MicroPython binary. Make sure you are connected to the network with wifi_connect and then simply<br /><i>import uftpd. </i>You may stop the server again with _uftpd.stop()_.

More information about the ftp server can be found at https://github.com/robert-hh/FTP-Server-for-ESP8266-ESP32-and-PYBD
---++ Telnet

A simple telnet server is included in the !MicroPython binary. To start it:

import utelnetserver<br />utelnetserver.start()<br /><br />Once started you can telnet to the ESP32 and connect to its REPL.

%BLUE% *Attention: This does NOT work when running the shell in thonny!* %ENDCOLOR%

Here is an example:

<img alt="utelnetserver.png" height="430" src="%ATTACHURL%/utelnetserver.png" title="utelnetserver.png" width="1230" />

On the left you have a minicom window connected to the ESP32 REPL through the serial line. On the right you have a window on the PC where I connect to the ESP32 REPL through telnet over the network.
---++ Exercises for the Internet part of the !IoT course

In this course we will have a look into two ways of accessing our data:
   * a [[WEB Server]] implemented on the ESP32
   * transfer of the data through [[MQTT to a Cayenne server]] offering display and logging of our data.
-- %USERSIG{UliRaich - 2020-04-28}%

---++ Comments

%COMMENT%

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	dateString.png	r1	manage	20.5 K	2020-06-01 - 12:30	UliRaich
png	hostname.png	r1	manage	22.0 K	2020-06-10 - 20:02	UliRaich
png	utelnetserver.png	r1	manage	100.5 K	2020-06-13 - 06:50	UliRaich
jpg	wifi_connect.jpg	r1	manage	105.4 K	2020-06-04 - 08:21	UliRaich
png	wifi_connect.png	r1	manage	30.9 K	2020-05-07 - 09:46	UliRaich
txt	wifi_connect.py.txt	r1	manage	2.5 K	2020-05-07 - 09:14	UliRaich
txt	wifi_connect_public.py.txt	r3 r2 r1	manage	3.5 K	2020-06-10 - 20:02	UliRaich

Topic revision: r10 - 2020-10-12 - UliRaich