B4A Library WebSocket Client Library

Erel said:

Don't confuse the server code (B4J) with B4A code.

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Erel said:

This library allows you to create WebSocket connections with servers that support WebSockets.
It is based on this open source project: http://autobahn.ws/android/#

The main benefit of this library is that you can use it to communicate with B4J WebApp solutions.

The attached example includes a class named WebSocketHandler. With this class you can send events to the server and the server can send events to the device.

View attachment 24449

The server code is very simple:

B4X:

Sub Class_Globals
   Private ws As WebSocket
   Private timer1 As Timer
End Sub

Public Sub Initialize

End Sub

Private Sub WebSocket_Connected (WebSocket1 As WebSocket)
   ws = WebSocket1
   timer1.Initialize("timer1", 1000)
   timer1.Enabled = True
End Sub

Sub Timer1_Tick
'This method will raise the event on the device
   ws.RunFunction("ServerTime", Array As Object(DateTime.Time(DateTime.Now)))
   ws.Flush
End Sub

'event from the device
Sub Device_Message(Params As Map)
   Log("Device message: " & Params.Get("message"))
End Sub

Private Sub WebSocket_Disconnected
   timer1.Enabled = False
   Log("disconnected")
End Sub

Sending events to the server

WebSocketHandler.SendEventToServer takes the event name (not prefix in this case) and the data. The data is a Map that is converted to a JSON string. Note that the event name must include an underscore.

B4X:

Sub btnSend_Click
   Dim data As Map
   data.Initialize
   data.Put("message", EditText1.Text)
   wsh.SendEventToServer("Device_Message", data)
End Sub

Receiving events from the server

B4X:

Sub wsh_ServerTime(Params As List)
   'example of a server push message
   lblServerTime.Text = "Server Time: " & Params.Get(0)
End Sub

The sub name in this case is made of the prefix set in the Initialize method and the event name as received from the server. There should be a single parameter which is a List.

How to run this example?

You need the latest version of B4J: http://www.b4x.com/android/b4j.html
Download and run the server example.
You will need to open the firewall port (51042).

Set the address in the client code to match the server address.

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Erel said:

This is not an error message. This information is always printed when you start the server.

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Erel said:

Not sure that I understand the question. Please start a new thread for it.

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Erel said:

This library allows you to send strings between the client and the server. You can encode the images with base64 encoding though it will not be very efficient.

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Erel said:

It doesn't matter whether it is an image or any other file. I don't recommend you to use this method for non-small files. Use regular server handler instead.

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Erel said:

I've already sent you to the relevant links many times.
https://www.b4x.com/android/forum/pages/results/?query=b4j server&page=1&prefix=18

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