WiFi - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 175

To connect to an open SSID (one that does not require a password), use only
the ssid parameter:

WiFi.begin(ssid);

To connect to a WPA-2 Personal protected network, specify the SSID and the
password:

WiFi.begin(ssid, password);

To connect to a WEP protected network, another parameter is required. WEP
protected networks can have up to four keys, and you must specify which one
to use:

WiFi.begin(ssid, keyIndex, key);

Both keys and SSIDs can be written as an array of chars :

char ssid[] = "yourNetworkSSID";
char password[] = "MySuperSecretPassword";

Status

Of course, initialization presumes that a WiFi shield is present and correctly
connected, which might not always be the case. To test for a WiFi shield, use
the status() function:

result = WiFi.status();

This function takes no parameters and returns one of several constants, as
shown in Table 10-1.

Table 10-1: Status Update Return Codes

CONSTANT MEANING

WL_IDLE_STATUS The WiFi shield is idle, without any instructions.

WL_NO_SSID_AVAIL There are no networks to connect to.

WL_SCAN_
COMPLETED

An initial SSID scan has been completed, and the WiFi shield
knows about available SSIDs.

WL_CONNECTED

The WiFi shield has successfully connected to an SSID.

WL_CONNECT_
FAILED

The WiFi shield was unable to connect; either the encryption key
is wrong, or the connection was refused by the access point.

WL_CONNECTION_
LOST

The WiFi shield was previously connected, but that connection
has been lost (either out of range, or interference).

Continues