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Why firefox do not show actual information from server after page reload?

I have made small web-app: http://letme.ijn.su
At this moment I debug it on PC.
I have problems with Firefox - when I make some changes on server side(add more notes) and resfresh page - I see changes only after some time. Other browsers(chrome, opera, yandex) work well
I suppose it is because of firefox cashing - how can I force it to get new info from server with every request?
I use Ubuntu, Apache, PHP.
by link http://letme.ijn.su - you launch index.php, which print job-page or login-page(have you cookies or not).

Maybe this will work clearstatcache(); This should clear the cache on the server side. Or if you want to delete a file you can use unlink();

I think clearing your browser cache will work best. Also, make sure to check the "Disable Cache" is the inspector settings. You can also try "View Page Source" in Firefox and refresh the newly-opened tab containing the page source.

How to debug WebSocket / Server Sent Events reconnections on desktop?

I am developing an app that uses Server Sent Events (SSE - basically one-way websockets). If the user uses the site on their mobile chrome browser and then tabs out for about a minute, the SSE connection breaks. If the user then tabs back into the site, it doesn't refresh the page (this is good). But I still need to re-establish the SSE connection so that the server can resume sending messages to them without a refresh.
I'm trying to debug my implementation but having to do it on mobile is very tedious. I have to grab my phone, refresh the page, then tab out, wait 1 minute (so the connection can break), and then tab back in to determine if my code for re-establishing the connection worked properly.
I would much rather be able to debug this on desktop, but I haven't found a way. I have tried the following:
Tried 5 different Chrome extensions for sleeping a tab. Unfortunately, when you navigate back into the tab it just refreshes the page rather than resumes it.
Tried using USB Debugging, but the desktop keeps the tab open at all times even if you tab out on mobile, so the tab never sleeps.
Tried running debugger; in the Chrome Developer Tools console, but even if I let the Javascript sit with its execution frozen for 5+ minutes, it never breaks the SSE connection, so I can't test if reconnecting works.
Tried using an extension to kill the internet for Chrome, but miraculously, this still maintains the active websocket/SSE connections. Apparently Google engineers have deprioritized this effort?
Basically, I am looking to simulate the behavior that happens on mobile when you tab out of your web browser, wait a minute, and then tab back in (the Javascript execution is frozen, the SSE connection is broken after a minute or so, and then tabbing back in resumes Javascript and attempts to reconnect the SSE connection).
Is this possible?

I think that best change you have by emulating your android device. You can do so by installing android studio from https://developer.android.com/studio and then here you have all you need to start and manage your virtual android env https://developer.android.com/studio/run/managing-avds
This it the way I debug my whole mobile development

The most obvious solution to me would be to attach a listener that tracks the events related to tab activation and build some custom solution upon that.
Simply:
window.onfocus = () => {
// Restore SSE session
};
window.onblur = function () {
// Inactive
};
Just for info, SSE is a different protocol from websockets.
In case you are interested in using websockets implementation, I suggest the following library which works very well in my experience: https://www.npmjs.com/package/#stomp/stompjs
Stomp is an abstraction over the websocket protocol, but it also means you would need to implement this on the server side as well.

You can use the chrome://discards to freeze your tab.
You should close and restore the connection based on the Page LifeCycle events.

You Can Try to use pause execution
goto:
Chrome javascript console (Ctrl+Shift+J) > sources > pause script (press f8)
This simulates like a mobile tab switching so you can debug easily
I think this is the simple and easy solution. thanks

Difference in IE browser interactions through Selenium and launching manually

Application in my project is very complex with number of backend systems and heavily written on javascript for frontend. Application works only in internet explorer and hence I am using InternetExplorerDriver.
I was successful in automating single browser window instance but when clicking some links which further opens new browser window where application is throwing "a javascript error occured"(error not with selenium). When I am doing the same flow manually by opening internet explorer and launching the application with URL then I am not seeing any error. I have tried all possible Desired Capabitilies and passed different values by trial and error method.
Also I have simulated mouse and keyboard events through Actions method when I am trying to click the link. None of them working for me.
So I am trying to understand is there any difference how selenium interacts with browser and how manually we interact with browser. Please help me on this one. Thanks in advance.

Can I make a socket connection through Javascript

What I want to do
Make a simple socket connection to a server on the browser. I want to not send any header information with the socket connection.
The Problem
It looks like I am unable to make a socket connection with javascript that does not send header data (Is there a way to do a tcp connection to an IP with javascript?).
I thought maybe I could make a connection with a chrome extension, however it looks like the socket API is only available for chrome apps (Google Chrome Socket API in extensions).
I am thinking that I might need to make a native application that will make socket connections through requests made by the browser using Native Messaging.
Is there anyway I can achieve this or am I out of luck?

Raw socket connections through the browser are wrapped up in security concerns. Users can be easily manipulated to allow things to run that shouldn't.
TCP and UDP Socket API
W3C Editor's Draft 20 January 2016
is located here.
http://raw-sockets.sysapps.org/
Mozilla's API information here: https://developer.mozilla.org/en-US/docs/Archive/B2G_OS/API/TCPSocket "This API is available on Firefox OS for privileged or certified applications only."
If you work with raw TCP connections. I would suggest
(1) downloading PHP onto the local computer. PHP has a developer web host build in so you can run whatever application you want on PHP using the browser as your GUI.
(2) download node.js.

You are not out of luck you just need to achieve it with the understanding that you are working outside the box for normal browser based scripting created from security concerns, and that means the user/client needs to install something manually.
If you must use chrome browser on the client side, you will need to make an -extension- correction webapp. You can as a developer make one that you can use on your own computers.
https://developer.chrome.com/extensions/getstarted
https://developer.chrome.com/apps/first_app
Load the extension#
Extensions that you download from the Chrome Web
Store are packaged up as .crx files, which is great for distribution,
but not so great for development. Recognizing this, Chrome gives you a
quick way of loading up your working directory for testing. Let's do
that now.
Visit chrome://extensions in your browser (or open up the Chrome menu
by clicking the icon to the far right of the Omnibox: The menu's icon
is three horizontal bars. and select Extensions under the Tools menu
to get to the same place).
Ensure that the Developer mode checkbox in the top right-hand corner
is checked.
Click Load unpacked extension… to pop up a file-selection dialog.
Navigate to the directory in which your extension files live, and
select it.
Alternatively, you can drag and drop the directory where your
extension files live onto chrome://extensions in your browser to load
it.
If the extension is valid, it'll be loaded up and active right away!
If it's invalid, an error message will be displayed at the top of the
page. Correct the error, and try again.
This insures that non developers don't load an extension which does not comply with the normal security concerns.
Communicating between with the script on the web page to the extension.
Can be done with message passing ... https://developer.chrome.com/extensions/messaging
The extension can add content directly to the web page which is available to the script on the web page. If for example the extension replaced the web cam image with a static image when the webcam script reads what it believes is the webcam it gets the static image instead, which explains why I look like an alien from space on the webcam. Although I did not create an extension to do that, I merely modified an existing extension to replace the function that gets the webcam image with a function to get a static image.

You can use SignalR, it is javascript library (JQuery Plugin) and it enables you to open web sockets from the browser to a server. Please check the following links:
https://blog.3d-logic.com/2015/03/29/signalr-on-the-wire-an-informal-description-of-the-signalr-protocol/
http://blog.teamtreehouse.com/an-introduction-to-websockets
https://github.com/SignalR/SignalR

Open a link in a specific browser

I have a web application which runs on all browsers but there is a link to another application which can only run in Internet Explorer. How I can force browser to open this link in a new IE browser when my application running in other browsers such as chrome? Should this piece of code written in server side or client side?

You can't force the client to launch a different browser like you're asking.
What I would suggest is to have your application test when it is launched to see if it is currently running in IE. If it isn't, it should issue an error message stating something like: "This application requires Internet Explorer. Please reopen in IE." Then have it stop there.

Most probably, using resources of JavaScript and HTML5, you cannot run applications on end user's computer. Moreover, it sounds incorrect in terms of security and usability.
The best thing you can do is to write a message like "Open this link in IE" near your link.
At the final page, you can detect a user's browser and, in case it is not an IE, show him a message "Unfortunately, this web-page works only with IE. Please, open it in IE".
By the way, could you tell us, why your page is not working in other browsers? Probably, we will find a proper answer there.