Upload from offline HTML5 app when network available - html

Wow, my problem seems like it must be so common that I must just be missing something really obvious but here goes:
Is there any way to trigger/schedule a dormant offline HTML5 app to run either:
when network comes available,
or regularly.
I want to create an offline HTML5 app that will record details of a delivery (item description, recipient's name, photo, timestamp, etc). The data will be written to local storage (the photo converted to base64). If the app has network then the delivery data will be uploaded to a remote server. If the app does not have network then, even if the user powers the device down, next time the device is up and has network, I need the app to do the upload without any action by the user.
I've searched and found nothing. I'm guessing that offline apps only get run-time when in the foreground? If someone could confirm that then that would at least be good to know, even if it's not what I'd like to hear.
Thanks

Background sync, exactly what I was after (although in 2016 it was Chrome-only):
https://developers.google.com/web/updates/2015/12/background-sync

Related

PWA vs html5 webapp?

I know that the most Iconic feature of PWA are
Service Worker: which make user can use the app offline from cached resources
Add To Home Screen: With this feature, user can add a shortcut of the app on their mobile home screen, to get a experience like interacting with a Native App(But there still a huge different, in my opinion)
etc.
However, I can do like all of them on about 6/7 years ago by using the HTML5 technology at that time, I know that service worker comes recently but there also was "HTML5 App Cache, as well as the Local Storage, Indexed DB, and the File API specifications." can do similar things.
Is there anyone can explain what's the difference between PWA and HTML5 webapps? or they are just the in term of same? or a similar concept but different implementation? or PWA is the (next gen/extension) of HTML5 webapp?
I might have some misunderstanding on PWAs, since I am new to this term, Thanks.
If keep it simple PWA is ordinary site with 3 additional features.
responsive design - site should look well on all devices
manifest.json - site must have general description about itself stored in manifest.json
caching - site must work offline
I believe 1 and 2 is easey. And 3 is realy what PWA is all about. So the question is: how we can provide offline support?
First problem is how we can get our initial .html .css and .js files without internet connection? Answer is: we should use service worker or App Cache. But App Cache has a lot of problems and probably will be deprecated, in other hand service worker under developement and become better each month. You can read more about their difference here.
Second problem is how we can get server data without internet connection? We should store most vital data somwhere. But after we get our .js file from cache we have access to Local Storage, Indexed DB etc. So we can store vital data in any of this storage while we online and get it back from them when we offline. It is totally up to you how you will handle that.
I believe there no cleare and strict defentiton for PWA and HTML5 webapp (at least for now). So you can asume it is the same but today PWA is more common word.

Alternative for Background Transfer Service to run uploads in background

I've used background transfer service (BTS) API for Windows Phone in two apps and experienced very bad problems. It became one of the main source of bug in the two apps as for some reasons, download are often refusing to start, whatever I set in the flags (Connected to wifi, not connected, connected to a power outlet, etc.), and it was random from a user to another. This and bad response from the servers.
Is there a more customized way to achieve it? Which threads or loop remains alive in my app when I'm navigating to the external:// world? I should probably check with counters.
My main question remains: appart from the BTS, is there something to allow a 3-4 megs file to upload even if I navigate out from my app to play an mp3 from an external:// app?
Once you exit your app, you are pretty much shut down. You can masquerade as a location tracking background agent to remain in the background when you get deactivated, though you'll suck battery and I believe there can only be one of these active at a time. Generally, highly not recommended (and you'll probably fail certification).
A better way to do this if BTS is not to your liking is to use a ResourceIntensiveTask. This will only be triggered when the user is plugged in and has WiFi but will allow you to run whatever you want for as long as the conditions are met (for example, at night) which should be plenty of time to upload a 3-4 MB file.

Access Control and Cache Manifest for Offline Use

I would like to gather some feedback on how best to handle access control within a web application that has a requirement for offline use.
The app must have access control via username/password but must be available for offline use. That means that the first time the user logs in, the user must have an internet connection. Once logged in the app will set an acl cookie followed by caching all assets through cache manifest.
Is this a solid approach and what other methods have you used to solve this issue?
Thank you in advance for all your feedback.
Answering quite late but even if you no longer need it someone else will...
Once offline, you need to store all access info on the device. It will be accessible by third parties so there will be a matter of time before someone will have access to all your app content. I explain to clients that once you publish something for offline use, it's there for anyone to see. You can implement some basic login but unless you use an online service, it's not going to be any secure...
Giving that, use local storage to keep track of initial login. Then, refresh it every so often when device goes online.

Shared HTML5 offline cache within a local network?

Ok, so I know that HTML in itself isn't done yet, and I've done my fair share of reading for HTML5's offline modes.
Here's the question:
Can I set up an offline app in such a way that the entire system works offline, and SHARES a cache (or an XML repository, or a SQL-Lite DB or something) with other clients in the SAME network?
For example, my system runs on clients that need to share information with each other within a local network, but its fully web based. In case the local network's router dies, how can these clients continue to communicate with one another?
=== END ===
NOTE: If you're still not clear, I'd recommend you read on. The information below is to further clarify what I want.
In case you're still reading, here's a detailed example:
4 people in a restaurant are using a web based ordering system. They each have an iPod Touch (lol) which is connected to the internet via Wifi. Each member logs in to the system under a shared account, which allows them to share information. The cook is also connected, but uses a mounted iPad (lolz) in the kitchen.
When a waiter records an order, the data is stored in a DB, and AJAX is used to constantly refresh the Cook's screen, so he is notified instantly.
Assume, Zeus struck down the electricity in the restaurant.
Now, there's no internet connection, but all devices in question still function thanks to their inherent battery-oriented nature.
The web app switches to offline mode, and utilizes cached menus and screens.
BUT!
How does the offline system share information between client devices? How does the iPod Touch #3 tell the Cook's iPad - "Hey there, this is order #5352"?
The most obvious thought is a shared cache or something...
Ideas?
That is not possible. WebPages cannot communicate without a server.
The only thing you could do is setting up a local server for the case that the server on the internet is offline or not reachable.

Interfacing with the end-user's scanner from a webapp (web/scanner integration)

Consider the following scanning procedure in a typical document handling webapp:
The user scans a document using a scanner connected to his/her computer
The scanned image is saved locally on the user's computer as a BMP/JPG/TIF/PNG file
The user hits a file upload "Browse.." button in the web application
The user is presented with a file dialog which he/she uses to locate the scanned image
The user hits "Upload image" and the scanned image is uploaded to the server where it is stored
This process is quite complicated and I'd like to reduce the number of steps in order to make the process more user friendly/fool proof. Under ideal circumstances the above steps would be replaced with only one step in which the procedure initiate document scanning, complete document scanning and upload resulting image is automatically triggered from the webapp when clicking say "Scan and upload". Unfortunely it seems like the state of "web/scanner integration" is quite poor so this might be utopia.
How would you tackle this problem? More specifically, how would you go about reducing the number steps involve in the use-case described?
Well, two years have passed, so here's an update on the state of the art for those just joining us.
Both Dynamsoft and Atalasoft have multi-browser web-scanning toolkits which are compatible with any server-side stack. Both require the user to install an ActiveX (in IE) or an NPAPI plugin (Chrome, Firefox, etc.) to get access to the scanner via the TWAIN API.
Obviously if you have the time or a limited budget, you can create your own plugin. I heartily recommend the FireBreath plugin framework, and any TWAIN library rather than writing your own TWAIN code.
Once the ActiveX or plugin is installed, the rest of the work is a combination of javascript & HTML on the client, and some kind of handler on the server to accept and process the incoming image, which can be made to look just like a multipart form submit with an attached file.
I recommend doing the image upload in javascript using AJAX, because it is then part of the same browser 'session' as the web page, and it inherits the browser's proxy settings, session cookies and server-side authentication. I don't know about Dynamsoft's control, the Atalasoft toolkit includes such AJAX uploading. The image(s) are handed from the plugin to the javascript as a base64-encoded string, so no local file is actually created.
Disclaimer: I work on Atalasoft's WingScan web-scanning toolkit.
If your target audience is running Windows and IE, and you don't mind spending a few $$, Atalasoft has some components that will do just what you're looking for.
I actually saw someone at the bank do this while setting up my account and I was totally amazed. Bank in question was using Windows and IE, I assume your in an equally controlled environment. I think the bank used a combination of a custom/ predictable scanner driver and an ActiveX control.
A page loaded which said "Open the scanner" the staff member popped the document in and hit Scan on the webpage, then the page changed to say Scanning, then it showed the scanned document on the web page for the staff member to Approve. I can only assume that the scanner driver send the image to a certain location and the active X control was polling for it to appear, once it appeared it showed the image on screen, once the staff member had approved it the active x uploaded it in the background. She opened the next page and carried on with the rest of the process.
God knows how they made all that tech work but it can be done.
Silverlight 4 is coming out soon. It is supposed to have the ability to interact with COM objects on the user's computer (provided they are running Windows). In theory you call WIA methods from your Silverlight web page.
We implemented a solution to implement Remote Deposit for a bank. It works only in IE. A winforms dll was created that interfaces with LeadTools TWAIN dll. Leadtools TWAIN dll abstracts all the TWAIN minutae. This approach is slighly better than using an ActiveX control. .NET Framework would be needed on client. The scanned images are posted back to a hidden variable on the page and are processed on the server.
Hmm, I've always wanted to look at a scanned file before I did anything with it, but I suppose that depends on your scanner and how much quality you need.
If the goal is to "automate the scanning and uploading process" as opposed to "write a web app", I'd write an AutoIt script to control the existing scanner software and a simple ftp program.
The option most likely to remove the most steps, would probably be writing a customized scan utility that the user would download and run on their local machine.
SANE or TWAIN would handle getting the scanned image. cURL could than handle uploading the image to your web app. To make things even easier for the end user, I would use something like a Comet connection to update the web page when the file was available.
If that isn't an option, you might look into seeing what options your users will likely have using their scanners software. I believe many programs now support scanning to email or ftp.
The solution I have used for an intranet app, using multifunction scanner/copiers was to scan to an SMB share that the web server had access to. The user just goes to the copier scans to the share and when they get back to their desk, they go to the new scans page which shows a list of all the new unprocessed files.
Since your audience is controlled environment, You can write your own browser extension/program based on WIA/TWAIN that does the scanning. If you choose browser extensions such as BHO/ActiveX/XPCOM, etc, you need get the user's permission to install your extension. If you choose to write a program you may need web deployment technologies like ClickOnce or Java Web Start to be launched from web.
Interfacing TWAIN is a pain on Windows. Complexity aside, you have to display some GUI written by different scanner driver developers. It may be the only way to support old scanners or features not exposed via other interfaces like full-speed multipage scans from a document feeder.
Microsoft's WIA makes interfacing with scanner much easier with a scripting object model, however scanner-specific features are not available and some old scanners do not support the interface.
After scanning you can call a web service to notify the server and the web page can refresh periodically to check new images.
We have done something similar. we used a command-line TWAIN program (http://www.burrotech.com/quickscan.php). $$ $49
1) We developed a small .Net application to run the QuickScan program as a shell command.
2) The command was assigned to the Scan button.
3) Once the user presses on the scan button, a prompt will appear to enter the file name. The user saves the transaction Id as the file name.
4) Another .Net application (or maybe the same mentioned before) will read this file and upload it into database considering that the filename is the transaction ID.
Worked like a warm knife in butter!
You can try displaying the transaction ID into IE, user to select the ID then presses Scan. Your application will read the SELECTED text and save the file using the SELECTED text as the file name. We havne't tried it but it should work.
It is only utopia if you think that web applications are limited to web browsers, in fact, web applications can include a lot of different technologies, besides HTML and Javascript.
The cool way of solving that problem -- in fact, I already used that for some usbserial devices -- is to implement your application using SOAP+XMPP. You can do that in Perl by using XML::CompileX::Transport::SOAPXMPP, Catalyst::Engine::XMPP2, Catalyst::Controller::SOAP and Catalyst::Model::SOAP.
The interesting thing about using XMPP is that it simplifies the management of addressing, since you use the JID (Jabber ID) to look for the software agent, not some host+port addressing schema. The second interesting part of using XMPP is to more easily support the server pushing information to the client.
But if you don't want to handle XMPP you still can do the same thing with a lightweight embedded http server -- HTTP::Server::Simple, in Perl -- and somehow register the current scanner address in the server so it can call back.
And a last option, which is not so cute, is to have the software agent polling the server to see when there is a "scan document and upload" order for that specific machine and realize that operation when that is present.
In summary, having a local software agent to interact with the local hardware doesn't make your webapp less "web", as long as you use web standards -- like XML, SOAP and others -- to perform that communication.
You can put a Java applet in your website. This can access the scanner and send the data via REST to your web server.