Client:Server:Sensor

The system for determining the deviation from a given course. Provides the ability to visualize data from the angular velocity sensor. As the server stands Raspberry Pi 3, configured to work in router mode. Client - any web browser.
Below is the general scheme for implementing the entire system.

Generalized structural scheme

An alternative is to read the data from the sensor using PHP language.
But this method is slower and it was necessary to abandon its application.

As an operating system for Raspberry Pi there can be chosen either Ubuntu-16.04 or Raspbian. A step-by-step configuration process for each system can be viewed below.
I recommend using Raspbian for 2 reasons. Firstly, the OS is optimized for working on Raspberry Pi. Secondly, the configuration process is much easier and will take less than an hour on average.

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Ubuntu-16.04

Server Start

Server installation lasts a fairly long time, about 30-40 minutes.

1. Use ubuntu-16.04 (ubuntu-16.04-preinstalled-server-armhf+raspi3.img);
2. Install LAMP:
   sudo apt-get install lamp-server^ phpmyadmin
sudo /etc/init.d/apache2 start
sudo chmod -R 777 /var/www
3. Install FTP-server:
   sudo apt-get install vsftpd
sudo systemctl start vsftpd
sudo systemctl enable vsftpd
sudo ufw allow 20/tcp
sudo ufw allow 21/tcp
sudo cp /etc/vsftpd.conf /etc/vsftpd.conf.orig
sudo nano /etc/vsftpd.conf
4. Edit ftp config /etc/vsftpd.conf:

anonymous_enable = NO  
local_enable = YES  
write_enable = YES  
local_umask = 022  
dirmessage_enable = YES  
xferlog_enable = YES  
xferlog_std_format=YES  
connect_from_port_20 = YES  
listen=YES  
listen_ipv6=NO  
pam_service_name=vsftpd  
userlist_enable = YES  
userlist_file=/etc/vsftpd.userlist  
userlist_deny=NO  

5. Create new user:
   sudo useradd -m -c "mplab" -s /bin/bash mplab
sudo passwd mplab
echo "mplab" | sudo tee -a /etc/vsftpd.userlist
cat /etc/vsftpd.userlist
6. Restart FTP-server;
7. Paste all project files from ./app into /var/www/html;
8. Start LAMP:
   sudo /etc/init.d/apache2 start
9. Move to server/index.php folder and start php server:
   cd /var/www/html/sensor/vendor/morozovsk/websocket-examples/chat/server/
php index.php start

Wi-Fi Hotspot Setup

1. Install hostapd:
   sudo apt-get install hostapd isc-dhcp-server
2. DHCP-server settings:
   sudo nano /etc/dhcp/dhcpd.conf

#option domain-name "example.org";  
#option domain-name-servers ns1.example.org, ns2.example.org;  
authoritative;  
subnet 192.168.42.0 netmask 255.255.255.0 {  
  range 192.168.42.10 192.168.42.50;  
  option broadcast-address 192.168.42.255;  
  option routers 192.168.42.1;  
  default-lease-time 600;
  max-lease-time 7200;  
  option domain-name "local";  
  option domain-name-servers 8.8.8.8, 8.8.4.4;  
}

3. Edit isc-dhcp-server: sudo nano /etc/default/isc-dhcp-server

INTERFACES=”wlan0″

4. Static ip configuration: sudo ifdown wlan0
sudo nano /etc/network/interfaces

#auto wlan0
allow-hotplug wlan0  
iface wlan0 inet static  
address 192.168.42.1  
netmask 255.255.255.0  

sudo ifconfig wlan0 192.168.42.1

5. WI-FI config:
   sudo nano /etc/hostapd/hostapd.conf

interface=wlan0
driver=nl80211
ssid=PI_sensor_v1
hw_mode=g
channel=6
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=mplabsensor
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

sudo nano /etc/default/hostapd

DAEMON_CONF=”/etc/hostapd/hostapd.conf”  

6. NAT settings:
   sudo nano /etc/sysctl.conf

net.ipv4.ip_forward=1  

sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
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"
sudo nano /etc/network/interfaces

up iptables-restore < /etc/iptables.ipv4.nat  

7. Updata hostapd(optional):
   wget http://adafruit-download.s3.amazonaws.com/adafruit_hostapd_14128.zip
unzip adafruit_hostapd_14128.zip
sudo mv /usr/sbin/hostapd /usr/sbin/hostapd.ORIG
sudo mv hostapd /usr/sbin
sudo chmod 755 /usr/sbin/hostapd

8. To startup:
   sudo service hostapd start
sudo service isc-dhcp-server start
sudo update-rc.d hostapd enable
sudo update-rc.d isc-dhcp-server enable

9. Other: sudo /usr/sbin/hostapd /etc/hostapd/hostapd.conf - start hostapd.
   sudo service hostapd status - hostapd status.
   sudo service isc-dhcp-server status - isc-dhcp-server status.

Possible issues:

1. Timeout for connection search eth0 in 5 minutes at system start.
   Solution:
   nano /lib/systemd/system/networking.service

TimeoutStartSec = 5sec  

2. You must enter a password to get started.
   Solution:
   nano /etc/systemd/system/getty.target.wants/getty@tty1.service

ExecStart=-/sbin/agetty --autologin mplab --noclear %I $TERM  

3. Adding the websocket server script to startup.
   nano /etc/rc.local
   Before "exit 0" add:

cd /var/www/html/vendor/morozovsk/websocket-examples/chat/server  
php /var/www/html/vendor/morozovsk/websocket-examples/chat/server/index.php start &  

4. Adding turn on button (https://geektimes.ru/post/255098/).
   nano /etc/rc.local
   Before "exit 0" add:

sudo bash /home/mplab/sys/shutdown.sh 

5. Fixing recursive fault but reboot is needed.
   No solution!

6. Problem with in-build UART (http://raspberrypi.ru/blog/627.html).
   Solution:
   Use external adapter CP2102 UART<->USB.

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Raspbian

Server Start

1. Install LAMP Server:
   sudo apt-get install apache2 -y
sudo a2enmod rewrite
sudo service apache2 restart sudo nano /etc/apache2/apache2.conf

<Directory /var/www/>  
 Options Indexes FollowSymLinks  
 AllowOverride All  
 Require all granted  
</Directory>  

sudo service apache2 restart

2. Install PHP:
   sudo apt-get install php libapache2-mod-php -y

3. Setup FTP:
   sudo apt-get install vsftpd -y
sudo nano /etc/vsftpd.conf

#local_enable=YES  
#ssl_enable=NO  
# CUSTOM  
ssl_enable=YES  
local_enable=YES  
chroot_local_user=YES  
local_root=/var/www  
user_sub_token=pi  
write_enable=YES  
local_umask=002  
allow_writeable_chroot=YES  
ftpd_banner=Welcome to my Raspberry Pi FTP service.  

sudo usermod -a -G www-data pi
sudo usermod -m -d /var/www pi
sudo chown -R www-data:www-data /var/www
sudo chmod -R 775 /var/www
sudo service vsftpd restart

Use to connect:

• Host – 192.xxx.x.xxx (IP address of your Pi with no prefix)
• Port – 21
• Protocol – FTP (File Transfer Protocol)
• Encryption – Use explicit FTP over TLS if available
• Logon Type – Normal (username & password)
• Username – pi
• Password – yourPass

Wi-Fi Hotspot Setup

1. Install Raspap:
   wget -q https://git.io/voEUQ -O /tmp/raspap && bash /tmp/raspap

2. Install hostapd:
   sudo apt-get install hostapd isc-dhcp-server

3. Customize interfaces.d:
   sudo nano /etc/network/interfaces.d

auto lo
iface lo inet loopback
auto eth0
allow-hotplug eth0
iface eth0 inet dhcp
allow-hotplug wlan0
iface wlan0 inet static
address 10.3.141.1
netmask 255.255.255.0

Set up auto-update

1. Change permissions on all files and folders:
   sudo chmod -R 777 var/www/html

2. Change owner for all files and folders in server dir:
   cd /var/www/html
sudo chmod www-data:www-data .

3. Create new local repo in var/www/html/upgrade

Important

Do not forget to rename default ```/var/www/html``` to arbitrary name. By default ```/var/www/html``` contain Raspap GUI web-interface. Create new html folder and place all files from whis repo.

Issues

1. Uncaught Error: Call to undefined mb_check_encoding
   Solution:

sudo apt-get install php7.0-mbstring
sudo service apache2 restart

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Other

After all the manipulations, you should get in var/www/html a similar structure:

client  
  css  
  img  
  js  
  svg  
service  
  bash  
  img  
  php  
upgrade  
  html  
  serial  
  service  
  update.php
vendor  
  composer  
  morozovsk  
  autoload.php  
gkv_udp_send  
index.html  
serial_start.sh  

Do not forget to copy QT libraries into usr/lib/
List of libraries: https://github.com/Shitovdm/client-server-sensor/blob/master/service/other/listQtLib.txt

To start the autorun, edit the file /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

echo 1 > /proc/sys/net/ipv4/ip_forward #RASPAP
iptables -t nat -A POSTROUTING -j MASQUERADE #RASPAP
sudo bash /var/www/html/service/bash/shutdown.sh &
cd /var/www/html/vendor/morozovsk/websocket-examples/chat/server
php index.php start &
exit 0

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Client

1. Connect to access point.
2. Go to local server address(http://10.3.141.1).

Interface

Explanations:

1. Units (grad/min).
2. Change the measurement limit of the instrument(range: 30-300, every 15).
3. Digital indicator of the exact value.
4. Settings button.
5. Save all in log button.
6. Current measurement limit.

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Resources:

https://github.com/morozovsk/websocket - PHP Websocket Class.
https://github.com/Xowap/PHP-Serial - PHP Serial Class.
https://github.com/hongkiat/svg-meter-gauge - Simple SVG-meter.
https://github.com/meetanthony/crcphp - Calculating CRC32 Class.
https://wiki.ubuntu.com/ARM/RaspberryPi - ubuntu-18.04-preinstalled-server-armhf+raspi3.img.xz (4G image, 295M compressed).
http://academicfox.com/raspberry-pi-besprovodnaya-tochka-dostupa-wifi-access-point/ - Hotspot on RasPi3. https://github.com/billz/raspap-webgui - Hotspot RPI Raspbian.
https://howtoraspberrypi.com/create-a-wi-fi-hotspot-in-less-than-10-minutes-with-pi-raspberry/ - Hotspot RPI Raspbian.