User manual

on the SRAM is mostly in the generous use of the practical but also resource-
consuming use of the String functions and generally the use of strings instead of
char-chains. A string.replace() is very practical, but it does eat up memory. If you
encounter inexplicable errors at some point, I recommend reducing the source
code of the HTML file and also possibly optimising some String operations. The
above Library can help you in troubleshooting.
4.8 | Insert: Accessing the board from the Internet
Many of the experiments presented here are practical for controlling the board in
your own home network. However, it can also be very useful to be able to reach
the board from larger distances. For example, you could switch on your lights at
home while on holiday to scare away burglars. You can also use the light sensor
to check if the light actually has been switched off. You could also send a mes-
sage to your family at home that you're running late. To put these ideas into prac-
tice, you need to make a few settings to your router.
Usually, different router types use different software. I will present the general
steps based on a Fritz!Box-router here. The settings in your router should be simi-
lar.
Most modern routers have a simple web interface similar to the one we have cre-
ated with the module. You need a user name and password to log on to the inter-
face. For Fritz!Box type routers, the IP usually is 192.168.178.1. You can also
enter http://fritz.box instead. If you use another router, you need to try and find out
the matching IP. Usually, the router uses the IP with address 1 in the subnet. If
your computer's IP is, e.g., 192.168.4.2, the IP if your router is most likely
192.168.4.1. The password and user name can usually be found on the rear of
your router or in the associated manual.
Once you are logged in to the user interface, you need to find the item port release
or port forwarding. In my Fritz!Box, it was under Internet -> Freigabe. Create a
new port rule. You need to choose the settings so that external queries to port 80
are forwarded to the IP of your board and port 80. The Fritz!Box menu has a sim-
plified setting. I only needed to select the item HTTP server and could choose
between existing IPs in the dropdown menu. The result should look similar on all
computers.