Save a image using nodejs, expressjs and socket.io - node.js

Question

I've tried to save a image to a specified directory with node.js using express.js and socket.io but it doesnt work.
On the client-side:
var reader = new FileReader();
function drop(e) {
e.stopPropagation();
e.preventDefault();
var dt = e.dataTransfer;
var files = dt.files;
jQuery.each(files, function(){
reader.onload = function(e) {
socket.emit('sendfile', e.target.result);
};
});
return false;
}
The image should be uploaded by a drag and drop function.
Then on the server-side:
io.sockets.on('connection', function (socket) {
[...]
socket.on('sendfile', function (data) {
var fs = require('fs');
app.use(express.bodyParser({ keepExtensions: true, uploadDir: '/uploaded' }));
io.sockets.emit('updatechat', socket.username, data); //test
});
I have also tried
socket.on('sendfile', function (data) {
var fs = require('fs');
fs.writeFile('/uploaded/test.png', data, "binary" , function (err) {
if (err) throw err;
console.log('It\'s saved!');
});
io.sockets.emit('updatechat', socket.username, data); //data test
});
but it doesnt saved anything.
The "data test" shows me, that the data are already were arrived on the server, so I don't think, that the problem comes from the client-side, but on the server-side I have no idea what I doing wrong

Answer 1

I made a simple example to illustrate the usage of file upload via socket!
The steps following are:
Create the send-file socket.io event to receive the file on app.js. This file received is a binary one;
In the jade/HTML page put an input file and a button to send it. NOTE: you don't have to use multipart to send a post with multipart content, we are sending socket files not a TCP request/response;
Initialize HTML5 File API support and prepare the listeners to watching out your file input component;
The rest of remaining routines to read the file and sent it content forward.
Now first step (app.js):
var io = require('socket.io').listen(8000, {log: false});
io.sockets.on('connection', function(socket) {
socket.on('send-file', function(name, buffer) {
var fs = require('fs');
//path to store uploaded files (NOTE: presumed you have created the folders)
var fileName = __dirname + '/tmp/uploads/' + name;
fs.open(fileName, 'a', 0755, function(err, fd) {
if (err) throw err;
fs.write(fd, buffer, null, 'Binary', function(err, written, buff) {
fs.close(fd, function() {
console.log('File saved successful!');
});
})
});
});
});
Second step (in my case I've used jade rather html)
extends layout
block content
h1 Tiny Uploader
p Save an Image to the Server
input#input-files(type='file', name='files[]', data-url='/upload', multiple)
button#send-file(onclick='javascript:sendFile();') Send
script(src='http://127.0.0.1:8000/socket.io/socket.io.js')
script(src='/javascripts/uploader.js')
Third and Fourth steps (coding uploader.js to send the file to server)
//variable declaration
var filesUpload = null;
var file = null;
var socket = io.connect('http://localhost:8000');
var send = false;
if (window.File && window.FileReader && window.FileList) {
//HTML5 File API ready
init();
} else {
//browser has no support for HTML5 File API
//send a error message or something like that
//TODO
}
/**
* Initialize the listeners and send the file if have.
*/
function init() {
filesUpload = document.getElementById('input-files');
filesUpload.addEventListener('change', fileHandler, false);
}
/**
* Handle the file change event to send it content.
* #param e
*/
function fileHandler(e) {
var files = e.target.files || e.dataTransfer.files;
if (files) {
//send only the first one
file = files[0];
}
}
function sendFile() {
if (file) {
//read the file content and prepare to send it
var reader = new FileReader();
reader.onload = function(e) {
console.log('Sending file...');
//get all content
var buffer = e.target.result;
//send the content via socket
socket.emit('send-file', file.name, buffer);
};
reader.readAsBinaryString(file);
}
}
Some important considerations:
This is a tiny sample of socket file uploader. I don't consider some important things here: file chunks to send piece of files instead of all content in a row; Update the status of file sent as (error msg, successful msg, progress bar or percent stage, etc.). So this is a sample to initial steps to coding your own file uploader. In this case, we don't need a form to send files, its is completely asynchronous transaction via socket.io.
I hope this post is helpful.

Answer 2

This tutorial goes a little bit further because you can pause/resume your upload but you will find how to upload a file through socketio :)