Question

I’m new to Ruby.
I’m trying to make an app that reads from a serial-port and puts values into a sqlite3 database. When a client connects via TCP socket he should recieve values from the db. Values written by the client should be sent via serial-port.

I have two questions regarding my app.

This would open one connection to the db on the main thread(?) and one for each client..
Is there a better way to use sqlite3?
I think i figured this out. sqlite3 is not thread safe by defaul,t so this seems like the way to do it..

How do i write to the serialport in the recieve_data method? Is it okay to make serial a global variable?

#!/usr/bin/env ruby
#
# server_1

require 'rubygems'
require 'eventmachine'
require 'sqlite3'
require 'em-serialport'
require 'json'

module SocketClient
    def self.list
        @list ||= []
    end

    def post_init
        SocketClient.list << self
        @db = SQLite3::Database.new( "data.db" )

        values = []
        @db.execute("SELECT * FROM values") do |row|
            values << {row[0] => row[1]} #id => value
        end
        self.send_data "#{values.to_json}\n"

        p "Client connected"

    end

    def unbind
        SocketClient.list.delete self
        @db.close
    end

    def receive_data data
        p data
        #How do i send via serialport from here??? serial.send_data data
    end
end

db = SQLite3::Database.new( "data.db" )

EM.run{
    EM.start_server '0.0.0.0', 8081, SocketClient
    serial = EM.open_serial '/dev/tty.usbserial-xxxxxxxx', 9600, 8, 1, 0

    serial.on_data do |data|
        #Parse data into an array called values
        db.execute("UPDATE values SET value = ? WHERE id = ?", values["value"], values["id"])
        SocketClient.list.each{ |c| c.send_data "#{values.to_json}\n" }
    end
}

db.close

Answer 1

Setup the constructor for your Socket client so that it will receive the shared serial connection.

module SocketClient
    def initialize serial
      @serial = serial
    end

    def receive_data data
        p data
        @serial.send_data data
    end

Then pass it when you call EM.start_server

EM.run{
    serial = EM.open_serial '/dev/tty.usbserial-xxxxxxxx', 9600, 8, 1, 0
    EM.start_server '0.0.0.0', 8081, SocketClient, serial