Reads data from a Mighty Ohm Geiger Counter that is connected via RS232, makes it available via a callback and a TCP socket.

radiation.js

/**
 * RADIATION WIDGET - SERVER BIT
 */

var
	serialport = require('serialport'),
	net = require('net');

exports.widget = function(eventTarget) {
	const CONFIG = {
		device: '/dev/ttyUSB3',
		srv: { bind: '0.0.0.0', port: 42420 },
	};

	const LINE_REGEXP = /^CPS, (\d+), CPM, (\d+), .+?, ([\d.]+), (SLOW|FAST)/;

	var prev_pushed = '';

	// --- from local/radiation/radiation.js ---
	var linebuf = {}, prev_time = Date.now();

	var sp = new serialport.SerialPort(CONFIG.device, {
		parser: serialport.parsers.readline("\n")
	})
	.on('data', function(line) {
		var now = Math.floor(Date.now() / 1000);

		if(!line)
			return;

		// max 1 sample per second:
		linebuf[now] = line;

		// discard accumulated data from serial buffer(s):
		if(Date.now() - prev_time < 0.5 * 1000) {
			linebuf = [];
		}
		else {
			for(var time in linebuf) {
				var line = linebuf[time].trim();

				if(line == prev_pushed) {
					continue;
				}

				var match = LINE_REGEXP.exec(line);

				if(match) {
					// "CPS, 0, CPM, 29, uSv/hr, 0.16, SLOW"
					var dat = {
						cps: parseInt(match[1]),
						cpm: parseInt(match[2]),
						usievert: parseFloat(match[3]),
						mode: (match[4] === 'SLOW' ? 0 : 1),
						raw: line,
					};

					eventTarget('geiger', dat);
					send_to_echo_clients(dat);
					prev_pushed = line;
				}
			}
			linebuf = [];
		}

		prev_time = Date.now();
	}).on('error', function(err) {
		console.log('Error in radiation.js: ' + err.message);
	});

	// -- TCP echo server --

	var srv_clients = [];

	if(CONFIG.srv) {
		net.createServer(function(socket) {
			srv_clients.push(socket);

			function discard_socket() {
				srv_clients = srv_clients.filter(function(s) { return (s !== socket); });
			}

			socket.on('close', discard_socket);
			socket.on('error', discard_socket);
		})
		.listen(CONFIG.srv.port, CONFIG.srv.bind);
	}

	function send_to_echo_clients(data) {
		if(srv_clients.length < 1)
			return;

		var line = JSON.stringify(data) + '\n';

		for(var i in srv_clients) {
			srv_clients[i].write(line);
		}
	}

};