05/12/2016 Added Gtk+-3.0 and GLib2.0 Display Services.

05/12/2016 Added GLib and GSSDP command line clients.

Package includes two features. One designed to both locate your Pi and provide a list of known services. The other acts as a central LCD display service, allowing other network devices/nodes to send a one-liners to the service for display on its LCD.

Each Raspberry Pi, Mac OSX, and Linux node in your network could execute udp_locator_service (LocatorService) as a backgound program using SystemD, a LaunchD PList, or an init script of some sort. The LocatorService collects the address of the machine it running on and creates a entry in its ServiceRegistry; which it sends to clients that requests it.

This establishes the network of locators, for which a udp_locator_client can poll at any time to find your Pi.

Likewise the lcd_display_service executes on nodes that also have an LCD Display of some sort; Serial/USB, MCP23008, or PCF8574 based. It is the provider of the shared LCD Display, and the target of the lcd_display_client (DisplayClient). DisplayClients query all LocatorServices for their active ServiceRegistry, and pickout the default lcd_display_service entry, or via command line option *–alt-service-name=my_service_name*.

Once a DisplayService is located, the DisplayClient sends a message to the DisplayService to display; from the command line *-m* option. Or if the DisplayClient has been started in *–non-stop=60* mode, it will send random status messages automatically to the DisplayService; in this case every 30 seconds.

Recent additions include a GTK+3 Display Service(gtkDS), a Plain Command Line Display Service(cmdDS), a GLIB-2.0 based Display Client(cmdDC), and a GSSDP based Display Client(gssdpDC). Note: gtkDS and cmdDS program include the udp_locator_service internally.

These apps were not intended to be final form applications. Instead they are well formed starters for your own projects.

Enjoy!

## Executables

Program	Type	Platform	Port	Description
*gtkDS	Server	any	48028	Maintains a list of known network services accessible via UDP socket, and offers the GTK display service.
*cmdDS	Server	any	48028	Maintains a list of known network services accessible via UDP socket, and offers the CmdLine display service.
udp_locator_service	Server	any	48028	Maintains a list of known network services accessible via UDP socket.
udp_locator_client	Client	any	n/a	Collect services info from Service, which includes that service's ip address.
*cmdDC	Client	any	n/a	Sends text one-liner to any display service.
lcd_display_service	Server	RPi	48029	Accepts one-line messages over udp and display them on a LCD panel.
lcd_display_client	Client	any	n/a	Sends one-liner composed of various Pi metrics; like cpus, temps, etc.
para_display_client	Client	Parallella	n/a	Sends one-liner with Zynq chip's temperature.
a2d_display_client	Client	Rpi	n/a	Sends one-liner with measured temp and light sensor values from AD/DA Shield Module For Raspberry Pi
*gssdpDC	Client	any	n/a	Sends text one-liner to any display service, after locating it using GSSDP/GUPNP.

### Configuration Options

Locator Service

upd_locator_service –help

udp_locator_service -- Provides IPv4 Addres/Port Service info.
          Skoona Development <skoona@gmail.com>
Usage:
  udp_locator_service [-v] [-s] [-m "<delimited-response-message-string>"] [-h|--help]
  udp_locator_service 
  udp_locator_service -s -a mcp_display_service
  udp_locator_service -m 'name=mcp_locator_service, ip=10.100.1.19, port=48028|'

Options:
  -a, --alt-service-name=my_service_name
                 *lcd_display_service* is default, use this to change name.
  -s, --include-display-service  Includes DisplaySerivce in default Registry response.
                *Presumes both are located on same machine; otherwise enter with '-m'*
  -m, --message  ServiceRegistry<delimited-response-message-string> to send.
  -v, --version  Version printout.
  -h, --help     Show this help screen.

  **ServiceRegistry Format:  _<delimited-response-message-string>_**
    delimited-response-message-string : required order -> name,ip,port,line-delimiter...
      format: "name=<service-name>,ip=<service-ipaddress>ddd.ddd.ddd.ddd,port=<service-portnumber>ddddd <line-delimiter>"
        name=<service-name> text_string_with_no_spaces
        ip=<service-ipaddress> ddd.ddd.ddd.ddd
        port=<service-portnumber> ddddd
      REQUIRED   <line-delimiter> is one of these '|', '%', ';'

    **example: -m "name=lcd_display_service,ip=192.168.1.15,port=48028|"**
    ** -m "name=rpi_locator_service, ip=10.100.1.19, port=48028|name=lcd_display_service, ip=10.100.1.19, port=48029|"**

udp_locator_client –help

udp_locator_client – Collect IPv4 Address/Port Service info from all providers. Skoona Development skoon.nosp@m.a@gm.nosp@m.ail.c.nosp@m.om Usage: udp_locator_client [-v] [-m 'any text msg'] [-u] [-a 'my_service_name'] [-h|–help] udp_locator_client udp_locator_client -u -a 'my_service_name'

Options: -a, –alt-service-name=my_service_name lcd_display_service is default, use this to change name. -u, –unique-registry List unique entries from all responses. -m, –message Any text to send; _'QUIT!' causes service to terminate._ _'**ADD **<delimited-response-message-string>' – add new registry entry into Service_ -v, –version Version printout. -h, –help Show this help screen.

Display Service.

Supports on the 'YwRobot Arduino LCM1602 IIC V1 LCD Backpack'

which uses the I2C controller PCF8574

example: **_lcd_display_service -r4 -c20 -t pcf_**

This is the default. example: **_lcd_display_service_**

Supports 'Adafruit IC2/SPI LCD Backpack'

which is based on the I2C controller MCP23008

example: **_lcd_display_service -r4 -c20 -t mcp_**

Supports 'Adafruit RGB Negative 16x2 LCD+Keypad Kit'

which is based on the I2C controller * MCP23017*

example: **_lcd_display_service -r2 -c16 -t mc7_**

Untested: I don't have one to test

Supports for 'Adafruit USB/Serial LCD Backpack'

which uses */dev/ttyACM0*

example: **_lcd_display_service -r2 -c16 -p /dev/ttyACM0 -t ser_**

Supports for 'AD / DA Shield Module For Raspberry Pi'

which is based on the I2C controller PCF8591T to access:

- on-board temperature sensor; NTC, MF58103J3950, B value 3950K, 1 K ohm 5% Cantherm

- on-board light sensors; GL5537-1 CdS Photoresistor

example: **_a2d_display_client -i 73_**

lcd_display_service –help

lcd_display_service -- LCD 4x20 Display Provider.
          Skoona Development <skoona@gmail.com>
Usage:
  lcd_display_service [-v] [-m 'Welcome Message'] [-r 4|2] [-c 20|16] [-i 39|32] [-t pcf|mcp|ser|mc7] [-p string] [-h|--help]

Options:
  -r, --rows=dd  Number of rows in physical display.
  -c, --cols=dd  Number of columns in physical display.
  -p, --serial-port=string Serial port.       | ['/dev/ttyACM0']
  -i, --i2c-address=ddd  I2C decimal address. | [0x27=39, 0x20=32]
  -t, --i2c-chipset=ccc  I2C Chipset.         | [pcf|mcp|ser|mc7]
  -m, --message  Welcome Message for line 1.
  -v, --version  Version printout.
  -h, --help     Show this help screen.

[lcd|para|a2d]_display_client –help

lcd_display_client -- Send messages to display service.
          Skoona Development <skoona@gmail.com>
Usage:
  lcd_display_client [-v] [-m 'text msg for display'] [-u] [-n] [-a 'my_service_name'] [-h|--help]
  lcd_display_client -u -m 'Please show this on shared display.'
  lcd_display_client -u -m 'Please show this on shared display.' -a 'ser_display_service'
  lcd_display_client -u -n 60 -a 'ser_display_service'
  lcd_display_client -u -n 60 -a 'mcp_display_service'
  para_display_client -n 330
  a2d_display_client -i 73 -n 330

Options:
  -a, --alt-service-name=my_service_name
                          *lcd_display_service* is default, use this to change name.
  -m, --message           Message to send to display, default: *$ uname -a output*
      _'**QUIT!**' causes service to terminate._
  -n, --non-stop=1|300    Continue to send updates every DD seconds until ctrl-break.
  -u, --unique-registry   List unique entries from all responses.
  -i, --i2c-address=ddd   I2C decimal address. | [0x49=73, 0x20=32]         
  -v, --version           Version printout.
  -h, --help              Show this help screen.

## Build: Autotools project

Requires WiringPi and assume the Pi is using Raspbian.

$ autoreconf -isfv            *Should not be required: use only if .configure produces errors*
$ ./configure
$ make
$ sudo make install

Only lcd_display_service requires WiringPi, builds automatically determine if wiringPi is available and build what is available to build.

## Notes:

WiringPi is a required library for display_service and some of the disply clients. If WiringPI is not present, which is the case with OSX and most Linuxs, then the autoconf will build the udp_locator_service and a limited set of clients. When WiringPi is available all services and clients are built.
Planning to write systemd unit scripts as part of package, add the following to rc.local for now.
- '/<path>/udp_locator_service >> /tmp/udp_locator_service.log 2>&1 &'
SINGLE QUOTES vs double quotes work a lot better for command line options.

## Known Issues:

08/08/2015 Found that concurrent I2C operations for LCD updates and reads from */sys/class/thermal/thermal_zone0/temp* cause the lcd_display_service to lockup with a process state of uninterruptible sleep. This is caused by the RPi's internal firmware, with no immediate resolution. To work around this issue, I have removed calls to getCpuTemp() from the lcd_display_service program.