檢視 Application - Wifi AP 的原始碼

[[File:DSC 2515.JPG|thumb|350px|Wifi AP with GPS]]
== USB wifi dongle ==
ID 148f:3572 Ralink Technology, Corp. RT3572 Wireless Adapter

== Software ==
sudo apt-get install hostapd udhcpd

=== dhcp server ===
*Edit the file /etc/udhcpd.conf and configure it like this:
<pre>
start 192.168.42.2 # This is the range of IPs that the hostspot will give to client devices.
end 192.168.42.20
interface wlan0 # The device uDHCP listens on.
remaining yes
opt dns 8.8.8.8 4.2.2.2 # The DNS servers client devices will use.
opt subnet 255.255.255.0
opt router 192.168.42.1 # The Pi's IP address on wlan0 which we will set up shortly.
opt lease 864000 # 10 day DHCP lease time in seconds
</pre>
*Edit the file /etc/default/udhcpd and change the line:
<pre>
DHCPD_ENABLED="no"
to
#DHCPD_ENABLED="no"
</pre>

=== Hostapd ===
*edit the file /etc/hostapd/hostapd.conf
<pre>
interface=wlan0
driver=nl80211
ssid=My_AP
hw_mode=g
channel=6
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=My_Passphrase
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP
</pre>

*Edit the file /etc/default/hostapd 
<pre>
#DAEMON_CONF=""
to:
DAEMON_CONF="/etc/hostapd/hostapd.conf"
</pre>

=== Configure NAT (Network Address Translation) ===
* fordwarding
sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
* iptables
<pre>
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"
up iptables-restore < /etc/iptables.ipv4.nat
</pre>

=== Service enable ===
* makae sure your runlevel
<pre>
$runlevel
N 5
</pre>
* make symbolic link to rcS
<pre>
cd /etc/init.d/rc5.d
# put udhcpd to the last
ln -s ../init.d/udhcpd S05udhcpd
ln -s ../init.d/hostapd S01hostapd
</pre>
* service
<pre>
sudo systemctl enable hostapd.service
sudo systemctl enable udhcpd.service
</pre>


== Reference ==
[http://elinux.org/RPI-Wireless-Hotspot, RPI-Wireless-Hotspot]