User manual

will then scan for all networks in the environment. When the network you are look-
ing for has been found, the function alarm() will be tripped, which switches on the
LED D3 and emits a signal sound at the piezo. In the example program, we scan
for a network with the SSID NanoESP, i.e. actually other NanoESP-networks in
range. You can also enter another SSID in #define ToFindSSID at the beginning of
the program. Then you can check, for example, how far your WLAN-network goes.
UDP AND IP
This chapter covers general data exchange between two systems via a WLAN-
network. We will deal with subjects such as IP, ports and the UDP protocol. First,
let us explain these basic terms.
What is an IP-address?
An IP-address works like a postal address. It can be used to clearly identify and
address a computer in the network. An IP-address according to the still-common
IPv4-standard looks as follows:
192.168.4.1
These are four numbers, or rather four bytes. This means that the value of each
number cannot exceed 255. Generally, there are local IP-addresses, i.e. IPs that
are assigned, e.g., to the computers and devices in your home network, and global
IPs.
Local IPs are usually assigned by your router. They usually start 192.168. The
following number differs from router to router. If the NanoESP acts as Access
Point and computers can connect to its network, PCs will receive an address that
starts with 192.168.4. This opens a subnetwork at the same time. Fritz!Box routers
usually assign local IP-addresses according to the structure 192.168.178.X. You
can find out your IP by entering, e.g. the command ipconfig in the Windows com-
mand prompt (under Start -> Programs -> Accessories -> Prompt ). A longer list
will appear, which includes, among others, the item IPv4-address with your local
IP in the network.
Global IPs are usually assigned by your internet service provider. This is, e.g., the
address via which your router can be reached in the global network. The router
opens the local network and distributes the data to the clients. One way of finding
out your global IP is calling the website http://www.meine-aktuelle-ip.de/. That
website shows further data that can be viewed by a web server as well. You are
not as anonymous online as you may think.