jQuery Ajax File Upload with Progress Bar

File upload should always have a progress bar. It is a feature that most of the developers ignore. It should be seen as part of the functionality. The users cannot sit in the dark and keep guessing about the background progress.

When the user requests the server to perform some operation, it is good to show them about the progress. It is a good UI/UX behaviour. The progress bar is one of the best ways to show the status of the in-progress operation. In this example, let us learn to create a progress bar using jQuery while uploading a file via AJAX.

A file input option is used to choose the file and the file binaries are posted to the server via AJAX. After sending the file upload request to the server, the AJAX script initializes jQuery animation to show the file upload progress bar. The progress bar will highlight the progressing percentage with jQuery animation. The jQuery Form plugin is used in this example code to handle the AJAX image upload with progressive status.

HTML Form with File Upload

The landing page will show a HTML form with the file input. Users will choose the file and post the file data by submitting the form via AJAX. The jQuery and jQuery Form library is included at the beginning of the script. A minimal jQuery validation script is added to check if the image file had been chosen before submitting the form.

AJAX Form Submit to Request Server File Upload with Progress bar

The jQuery form library is used to submit the form via AJAX with an animated progress bar. The ajaxForm() function is used to submit the image file binaries to the PHP. The progress of the image upload is shown with a progress bar in the uploadProgress callback function. Also, the jQuery animate() method is called to create the progressing effect on the progress bar element.

 

VOIP In Matrix JS SDK

This module outlines how two users in a room can set up a Voice over IP (VoIP) call to each other. Voice and video calls are built upon the WebRTC 1.0 standard. Call signalling is achieved by sending message events to the room. In this version of the spec, only two-party communication is supported (e.g. between two peers, or between a peer and a multi-point conferencing unit). This means that clients MUST only send call events to rooms with exactly two participants.

For a complete overview of Matrix Javascript SDK configuration, please go to our Matrix Javascript SDK.

Matrix Javascript SDK

Establish a call

This method is call by the caller when they wish to establish a call.

For voice call

For video call

Incoming call event for callee

Callee answer the call

This method is call by the callee when they wish to answer the call.

Hangup the call

Method call by either party to signal their termination of the call. This can be sent either once the call has has been established or before to abort the call.

Examples

 

Still Confused With SMTP, IMAP, POP Ports?

Configuring SMTP, IMAP and POP ports can be confusing. Users and sometimes even system administrators aren’t sure when to use port 25, 587, or 465.

This article will clarify all ports related to the mail server.

SMTP 25
SMTP-SSL/TLS 587,465
IMAP 143
IMAP-SSL/TLS 993
POP3 110
POP3-SSL/TLS 995

IMAP uses port 143, but SSL/TLS encrypted IMAP uses port 993.

POP uses port 110, but SSL/TLS encrypted POP uses port 995.

SMTP uses port 25, but SSL/TLS encrypted SMTP uses port 465.

587 vs. 465
These port assignments are specified by the Internet Assigned Numbers Authority (IANA):

Port 587: [SMTP] Message submission (SMTP-MSA), a service that accepts submission of email from email clients (MUAs). Described in RFC 6409.
Port 465: URL Rendezvous Directory for SSM (entirely unrelated to email)
Historically, port 465 was initially planned for the SMTPS encryption and authentication “wrapper” over SMTP, but it was quickly deprecated (within months, and over 15 years ago) in favor of STARTTLS over SMTP (RFC 3207). Despite that fact, there are probably many servers that support the deprecated protocol wrapper, primarily to support older clients that implemented SMTPS. Unless you need to support such older clients, SMTPS and its use on port 465 should remain nothing more than a historical footnote.

Howto list all instances in all regions from mutliple accounts using awscli – AWS

AWS Cloud spans 69 Availability Zones within 22 geographic regions around the world, with announced plans for 9 more Availability Zones and three more Regions in Cape Town, Jakarta, and Milan.

If you are using more than one region it takes much time to browse through all regions in a browser and check which instances are running.

To save time, we are using awscli command in a shell script which will list all instances from all regions. You can use multiple profile names.

scrot

 

You can specify multiple profile names as follows:

This will run jobs in parallel and exit when all jobs are completed.

Locking your bash script against parallel execution

Sometimes there’s a need to ensure only one copy of a script runs, i.e prevent two or more copies running simultaneously. Imagine an important cronjob doing something very important, which will fail or corrupt data if two copies of the called program were to run at the same time. To prevent this, a form of MUTEX (mutual exclusion) lock is needed.

The basic procedure is simple: The script checks if a specific condition (locking) is present at startup, if yes, it’s locked – the script doesn’t start.

This article describes locking with common UNIX® tools.

Method 1

setting the noclobber shell option (set -C). This will cause redirection to fail, if the file the redirection points to already exists (using diverse open() methods). Need to write a code example here.

 

Method 2

A simple way to get that is to create a lock directory – with the mkdir command. It will:

create a given directory only if it does not exist, and set a successful exit code
it will set an unsuccessful exit code if an error occurs – for example, if the directory specified already exists
With mkdir it seems, we have our two steps in one simple operation. A (very!) simple locking code might look like this:

In case mkdir reports an error, the script will exit at this point – the MUTEX did its job!

React Quickstart Tutorial

React is a JavaScript library created by Facebook.
ReactJS is a tool for building UI components.

Adding React to an HTML Page

This quickstart tutorial will add React to a page like this:

Example


What is Babel?

Babel is a JavaScript compiler that can translate markup or programming languages into JavaScript.

With Babel, you can use the newest features of JavaScript (ES6 – ECMAScript 2015).

Babel is available for different conversions. React uses Babel to convert JSX into JavaScript.

Please note that is needed for using Babel.


What is JSX?

JSX stands for JavaScript XML.
JSX is an XML/HTML like extension to JavaScript.

Example

As you can see above, JSX is not JavaScript nor HTML.

JSX is a XML syntax extension to JavaScript that also comes with the full power of ES6 (ECMAScript 2015).

Just like HTML, JSX tags can have a tag names, attributes, and children. If an attribute is wrapped in curly braces, the value is a JavaScript expression.

Note that JSX does not use quotes around the HTML text string.

React DOM Render

The method ReactDom.render() is used to render (display) HTML elements:

Example


JSX Expressions

Expressions can be used in JSX by wrapping them in curly {} braces.

Example


React Elements

React applications are usually built around a single HTML element.

React developers often call this the root node (root element):

React elements look like this:

Elements are rendered (displayed) with the ReactDOM.render() method:

React elements are immutable. They cannot be changed.

The only way to change a React element is to render a new element every time:

Example


React Components

React components are JavaScript functions.

This example creates a React component named “Welcome”:

Example

React can also use ES6 classes to create components.

This example creates a React component named Welcome with a render method:

Example


React Component Properties

This example creates a React component named “Welcome” with property arguments:

Example

React can also use ES6 classes to create components.

This example also creates a React component named “Welcome” with property arguments:

Example


 JSX Compiler

The examples on this page compiles JSX in the browser.

For production code, the compilation should be done separately.


Create React Application

Facebook has created a Create React Application with everything you need to build a React app.

It is a a development server that uses Webpack to compile React, JSX, and ES6, auto-prefix CSS files.

The Create React App uses ESLint to test and warn about mistakes in the code.

To create a Create React App run the following code on your terminal:

Example

Make sure you have Node.js 5.2 or higher. Otherwise you must install npx:

Example

Start one folder up from where you want your application to stay:

Example

Success Result:

Apple iOS App Provisioning

A distribution certificate identifies your team/organization within a distribution App Provisioning profile and allows you to submit your app to the Apple App Store.

The workflow for developing and distributing iOS apps can be complex and difficult to understand. This article explain the steps needed to manage certificates and provisioning profiles and assist developer who are starting to develop in-house iOS apps.

A provisioning profile is a collection of digital entities that uniquely ties developers and devices to an authorized iPhone Development Team and enables a device to be used for testing.

The following steps describe the high level activities required to manage and distribute apps.

  1. Manage Certificates for development and production
    1. Create certificate for Development
    2. Create certificate for Production
  2. Register AppId and DeviceId
    1. Add Device ID’s
    2. Register AppID’s
  3. Create App Provisioning Profiles for Project
    1. Create Provisioning Profile for Developement & Production
    2. Apply AppID to Provisioning Profile
    3. Apply Certificate to App Provisioning Profile
    4. Download Profile and add it in Xcode

Step 1: Login

Go to https://developer.apple.com and click on Account (you must have an Apple Developer account to begin)

1. Click Log In, choose Select Certificates, Identifiers & Profiles

Step 2 : create Certificate

On the left menu select Certificates

1. Select add button “+” at the top right to create a new Certificate

2. Select “iOS Distribution (App Store and Ad Hoc)” and press Continue

3. Developers will need to generate a Certificate Signing Request (CSR) from their keychain and perform the Request Certificate function. Then select Signing certificate and Generate and Download certificate.

4. Click on Downloaded Certificate, it will added to KeyChain.

Step 3 : RegisterAppID

  1. From the left menu select Identifiers -> Click on Add new -> Select AppID’s
  2. Describe Name, and paste your project’s BundleID and select Capability which your app provides
  3. Click On Register Button. Now your AppID is Registered.

Step 4 : Create App Provisioning Profile

On the left tab under Provisioning Profiles, select Distribution

1. Select add button “+” at the top right to create a new profile

2. Select “App Store” and press Continue

iOS Provisioning Profile

 

 

3. Select App ID and press Continue

 

iOS Provisioning Profile

 

 

4. Select the Certificate you wish to include in this provisioning profile (the certificate the app was signed with) and click Continue. Next, select the devices you wish to include in the provisioning profile. The certificate is a public/private key-pair, which identifies who developed the app.

 

5. Create a name for your profile and click Generate. You might want to include “Distribution” in the name so you can distinguish this one from testing.

6. Download Your Profile and by clicking it will be added to Xcode.

 

Howto reverse proxy in nginx

Proxying is typically used to distribute the load among several servers, seamlessly show content from different websites, or pass requests for processing to application servers over protocols other than HTTP.

When NGINX proxies a request, it sends the request to a specified proxied server, fetches the response, and sends it back to the client. It is possible to proxy requests to an HTTP server (another NGINX server or any other server) or a non-HTTP server (which can run an application developed with a specific framework, such as PHP or Python) using a specified protocol.

1. To pass a request to an HTTP proxied server, the proxy_pass directive is specified inside a location. For example:

 2. This address can be specified as a domain name or an IP address. The address may also include a port:

3. To pass a request to a non-HTTP proxied server, the appropriate **_pass directive should be used:

  • fastcgi_pass passes a request to a FastCGI server
  • uwsgi_pass passes a request to a uwsgi server
  • scgi_pass passes a request to an SCGI server
  • memcached_pass passes a request to a memcached server

4. Passing Request Headers

 

5. To disable buffering in a specific location, place the proxy_buffering directive in the location with the off parameter, as follows:

 

 

Matrix Javascript SDK

Matrix Client-Server r0 SDK for JavaScript. This SDK can be run in a browser or in Node.js.

Quickstart

In a browser

Download either the full or minified version from https://github.com/matrix-org/matrix-js-sdk/releases/latest and add that as a <script> to your page. There will be a global variable matrixcs attached to window through which you can access the SDK. See below for how to include libolm to enable end-to-end-encryption.

Please check the working browser example for more information.

In Node.js

Ensure you have the latest LTS version of Node.js installed.

Using yarn instead of npm is recommended. Please see the Yarn install guide if you do not have it already.

yarn add matrix-js-sdk

See below for how to include libolm to enable end-to-end-encryption. Please check the Node.js terminal app for a more complex example.

To start the client:

You can perform a call to /sync to get the current state of the client:

To send a message:

To listen for message events:

By default, the matrix-js-sdk client uses the MemoryStore to store events as they are received. For example to iterate through the currently stored timeline for a room:

What does this SDK do?

This SDK provides a full object model around the Matrix Client-Server API and emits events for incoming data and state changes. Aside from wrapping the HTTP API, it:

  • Handles syncing (via /initialSync and /events)
  • Handles the generation of “friendly” room and member names.
  • Handles historical RoomMember information (e.g. display names).
  • Manages room member state across multiple events (e.g. it handles typing, power levels and membership changes).
  • Exposes high-level objects like Rooms, RoomState, RoomMembers and Users which can be listened to for things like name changes, new messages, membership changes, presence changes, and more.
  • Handle “local echo” of messages sent using the SDK. This means that messages that have just been sent will appear in the timeline as ‘sending’, until it completes. This is beneficial because it prevents there being a gap between hitting the send button and having the “remote echo” arrive.
  • Mark messages which failed to send as not sent.
  • Automatically retry requests to send messages due to network errors.
  • Automatically retry requests to send messages due to rate limiting errors.
  • Handle queueing of messages.
  • Handles pagination.
  • Handle assigning push actions for events.
  • Handles room initial sync on accepting invites.
  • Handles WebRTC calling.

Later versions of the SDK will:

  • Expose a RoomSummary which would be suitable for a recents page.
  • Provide different pluggable storage layers (e.g. local storage, database-backed)

 Usage

 Conventions

 Emitted events

The SDK will emit events using an EventEmitter. It also emits object models (e.g. Rooms, RoomMembers) when they are updated.

Promises and Callbacks

Most of the methods in the SDK are asynchronous: they do not directly return a result, but instead return a Promise which will be fulfilled in the future.

The typical usage is something like:

Alternatively, if you have a Node.js-style callback(err, result) function, you can pass the result of the promise into it with something like:

The main thing to note is that it is an error to discard the result of a promise-returning function, as that will cause exceptions to go unobserved. If you have nothing better to do with the result, just call .done() on it. See http://documentup.com/kriskowal/q/#the-end for more information.

Methods which return a promise show this in their documentation.

Many methods in the SDK support both Node.js-style callbacks and Promises, via an optional callback argument. The callback support is now deprecated: new methods do not include a callback argument, and in the future it may be removed from existing methods.

Examples

This section provides some useful code snippets which demonstrate the core functionality of the SDK. These examples assume the SDK is setup like this:

Automatically join rooms when invited

Print out messages for all rooms

Output:

Print out membership lists whenever they are changed

Output:

API Reference

A hosted reference can be found at http://matrix-org.github.io/matrix-js-sdk/index.html

This SDK uses JSDoc3 style comments. You can manually build and host the API reference from the source files like this:

Then visit http://localhost:8005 to see the API docs.

End-to-end encryption support

The SDK supports end-to-end encryption via the Olm and Megolm protocols, using libolm. It is left up to the application to make libolm available, via the Olm global.

It is also necessry to call matrixClient.initCrypto() after creating a new MatrixClient (but before calling matrixClient.startClient()) to initialise the crypto layer.

If the Olm global is not available, the SDK will show a warning, as shown below; initCrypto() will also fail.

If the crypto layer is not (successfully) initialised, the SDK will continue to work for unencrypted rooms, but it will not support the E2E parts of the Matrix specification.

To provide the Olm library in a browser application:

To provide the Olm library in a node.js application:

  • yarn add https://packages.matrix.org/npm/olm/olm-3.0.0.tgz (replace the URL with the latest version you want to use from https://packages.matrix.org/npm/olm/)
  • global.Olm = require('olm'); before loading matrix-js-sdk.

If you want to package Olm as dependency for your node.js application, you can use yarn add https://packages.matrix.org/npm/olm/olm-3.0.0.tgz. If your application also works without e2e crypto enabled, add --optional to mark it as an optional dependency.

Contributing

This section is for people who want to modify the SDK. If you just want to use this SDK, skip this section.

First, you need to pull in the right build tools:

Building

To build a browser version from scratch when developing::

To constantly do builds when files are modified (using watchify)::

To run tests (Jasmine)::

To run linting:

WSL vs WSL 2 – performance

WSL 2 is a new version of the architecture that powers the Windows Subsystem for Linux to run ELF64 Linux binaries on Windows. Its primary goals are to increase file system performance, as well as adding full system call compatibility. This new architecture changes how these Linux binaries interact with Windows and your computer’s hardware, but still provides the same user experience as in WSL 1 (the current widely available version). Individual Linux distros can be run either as a WSL 1 distro, or as a WSL 2 distro, can be upgraded or downgraded at any time, and you can run WSL 1 and WSL 2 distros side by side. WSL 2 uses an entirely new architecture that uses a real Linux kernel.

It’s a major reworking of the original WSL concept, moving away from translating Linux system calls to Windows to shipping a complete Linux kernel that runs alongside Windows’ own kernel.

The reasons for doing this are many, but the main one is simple: It’s impossible for an emulator that ships twice a year to keep up with the changes in the Linux kernel, changes that Linux binaries depend on. If Windows is to support developers building Linux apps for the cloud, then it needs to be more than consistent, it needs to be compatible.

 

Linux kernel in WSL 2

The Linux kernel in WSL 2 is built in house from the latest stable branch, based on the source available at kernel.org. This kernel has been specially tuned for WSL 2. It has been optimized for size and performance to give an amazing Linux experience on Windows and will be serviced through Windows updates, which means you will get the latest security fixes and kernel improvements without needing to manage it yourself.

Increased file IO performance

File intensive operations like git clone, npm install, apt update, apt upgrade, and more will all be noticeably faster. The actual speed increase will depend on which app you’re running and how it is interacting with the file system. Initial versions of WSL 2 run up to 20x faster compared to WSL 1 when unpacking a zipped tarball, and around 2-5x faster when using git clone, npm install and cmake on various projects.

Sockets performance benchmarks

WSL

wsl

 

WSL 2

wsl2

The Ubuntu 18.04 LTS WSL instance was used for testing with its default packages. In addition to looking at the WSL1 vs. WSL2 performance of Ubuntu 18.04, Ubuntu 18.04.2 LTS itself was also tested bare metal on the same system for looking at the raw performance of Ubuntu on the Intel desktop being tested.

Full System Call Compatibility

Linux binaries use system calls to perform many functions such as accessing files, requesting memory, creating processes, and more. In WSL 1 we created a translation layer that interprets many of these system calls and allows them to work on the Windows NT kernel. However, it’s challenging to implement all of these system calls, resulting in some apps being unable to run in WSL 1. Now that WSL 2 includes its own Linux kernel it has full system call compatibility. This introduces a whole new set of apps that you can run inside of WSL. Some exciting examples are the Linux version of Docker, as well as FUSE!

Using WSL 2 means you can also get the most recent improvements to the Linux kernel much faster than in WSL 1, as we can simply update the WSL 2 kernel rather than needing to reimplement the changes ourselves.

WSL 2 will be a much more powerful platform for you to run your Linux apps on and will empower you to do more with a Linux environment on Windows.