Multiple Serialport reads after reloading webpage in node.js

Question

Multiple Serialport reads after reloading webpage in node.js

I am trying to use node.js on a Raspberry Pi to interface a serial device. I want to send data from the device to a webpage, send control data from the webpage to the device and log and store data on the Pi. When I run this:

var fs = require('fs');
var http = require('http');
var server = http.createServer(function(req, res){
    res.writeHead(200, { 'Content-type': 'text/html'});
    res.end(fs.readFileSync(__dirname + '/engComp.html'));
    }).listen(8080, function(){console.log('Listening at: http://localhost:8080');});
var io = require('socket.io').listen(server);
var serialport = require("serialport");
var SerialPort = serialport.SerialPort;
var sp = new SerialPort("/dev/ttyAMA0", {
    baudrate: 9600,parser: serialport.parsers.readline('\r')});

sp.open(function (){console.log('serial port open');
    io.on('connection', function (socket){
        console.log('socket open');
        socket.on('data',function(recData){   //data recieved from socket
            console.log('http rec data = '+recData);
            sp.write(recData, function(err, results){
                console.log('serial port send data = '+recData);
            });
        });
        sp.on('data', function(sdata){        //data recieved from serial port
            console.log('serial port rec sdata = ' + sdata);
        });
        socket.on('disconnect', function (){
            console.log('socket disconnect');
//            sp.close(function(){
//                console.log('serial port closed');
//            });
        });
    });
});

and reload the page say 3 times I get 3 outputs for each serial data read.

If I put back (un-rem) the sp.close() it works until I reload as expected (the port is closed but never reopened).

If I put the sp.open() in the io.on(connection) callback and serial data comes in while the page is reloading (after sp.close() but before sp.open() it crashes with:

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: EBADF, read

I would prefer not to close the port durring a reload as this would interfere with loging to the Pi.

I am using node v0.10.26 but same thing happens with v0.8.17

node.js
node-serialport

Answer 1

Operating on the assumption that you intend for there to only be one serial connection open and one website connection open, try something like this.

var fs = require('fs');
var http = require('http');
var server = http.createServer(function(req, res) {
    res.writeHead(200, { 'Content-type': 'text/html'});
    res.end(fs.readFileSync(__dirname + '/engComp.html'));
});

var io = require('socket.io').listen(server);

var SerialPort = require('serialport').SerialPort;
var sp = new SerialPort('/dev/ttyAMA0', {
    baudrate: 9600,
    parser: serialport.parsers.readline('\r')
});

io.on('connection', function (socket) {
  console.log('socket open');

  socket.on('data', function(recData) {
    console.log('http rec data =', recData);
    sp.write(recData, function(err, results){
        console.log('serial port send data =', recData);
    });
  });
});

sp.open(function () {
  console.log('serial port open');

  server.listen(8080, function(){
    console.log('Listening at: http://localhost:8080');
  })

  sp.on('data', function(sdata) {
    io.emit('sdata', sdata);
    console.log('serial port rec sdata = ', sdata);
  });
});

Now there is only one serial port connection opened and it doesn't open / close between requests. Furthermore, the website only starts listening for connections after the serial port has been opened and is ready for data.