B4J Tutorial Consuming http streams

Standard http communication is made of a request being sent from the client to the server and the server response sent back to the client.
As I'm sure you know you should use OkHttpUtils2 for such requests.

There are other protocols such as WebSockets that allow bi-directional and long lasting communication between the client and server.

There are some cases where the server keeps the connection open and streams data to the client. Assuming that WebSockets are not used then such cases require non-standard handling.

The attached MJPEG class uses a custom OutputStream (implemented with inline Java) together with B4XBytesBuilder to read the data as it comes and keep the connection open.
It is a port of this decoder, which was implemented with raw sockets and AsyncStreams.
The Data_Available event is raised whenever new data is available.

Note that this code can be easily ported to B4A.

If making many connections at the same time then it is better to move OkHttpClient out of the class and reuse it.

 

[Erel]

Added an option to disconnect the connection.

 

[jcesar]

Hi

Can i use this code to stream audio from a online radio ?

 

[Erel]

Worth trying. Test it with jAudioTrack: https://www.b4x.com/android/forum/threads/jaudiotrack.37973/#content

 

[woniol]

Hi,

Can we have an exmaple code ported to B4A.
With the original custom OutputStream does not work with B4A.

 

[Erel]

Please post your B4A project and explain what "does not work" means.

 

[LucaMs]

Can you choose a better webcam, please? ?

 

[woniol]

Changed:

Private const PackageName As String = "b4j.example" '<------ change as needed

to

Private const PackageName As String = "b4a.example" '<------ change as needed

and it works like a charm

 

[Hypnos]

Can this example run on raspberry pi ? I tried but no image display...

 

[Erel]

The code itself should work. Test it on the PC first, it is possible that the mjpeg stream used in that example is no longer working.

 

[Hypnos]

The code itself should work. Test it on the PC first, it is possible that the mjpeg stream used in that example is no longer working.

I think it may related to the java/jfx version on raspberry pi, I followed below post to change to another version and I can see the webcam image but this time I got some other issue (e.g. button not work, screen background changed to black... etc..) : (

Using JavaFX on Raspberry Pi 3 with Gluon

In this post, I am going to detail the steps to get a simple JavaFX application running on the Raspberry Pi 3 using Gluon. Hardware For this setup, I used the Raspberry Pi 3 with the official 7" touchscreen connected. Raspbian Installation First off, download Raspbian from...

www.wimdeblauwe.com

 

[Johan Hormaza]

Note that this code can be easily ported to B4A.

Note that this code can be easily ported to B4A.

And for B4i?

 

[GMan]

May be simple as this (don't know) ?

Private const PackageName As String = "b4i.example" '<------ change as needed

 

[Johan Hormaza]

May be simple as this (don't know) ?

Private const PackageName As String = "b4i.example" '<------ change as needed

It's not that easy

 

[Erel]

This will not work with B4i. The underlying http methods are completely different. The low level solution does work with B4i: https://www.b4x.com/android/forum/threads/b4x-class-mjpeg-decoder.73702/#content

 

[b4x-de]

There was a discussion on this line:

Private const PackageName As String = "b4i.example" '<------ change as needed

Instead of updating this line in every new project that uses a different package name, you could be more flexible with the following solution on B4J. It allows you to include the class in a library without worrying about the package name.

' ...
Dim strFullClassName As String
Dim joMe As JavaObject

joMe = Me
strFullClassName = joMe.RunMethod("getFullQualifiedClassname", Null)
out.InitializeNewInstance($"${strFullClassName}$MyOutputStream"$, Array(Me))

' ...

#If Java

public String getFullQualifiedClassname() {

 return this.getClass().getName();

}

#End If