B4A Library WebSocket Client Library

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Erel

Administrator
Staff member
Licensed User
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.

upload_2014-4-23_15-54-47.png


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.basic4ppc.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.

Updates

v2.11: New Headers Map that can be used to add headers to the upgrade request (https://www.b4x.com/android/forum/threads/websocketclient-authorization.116574/#post-729213)
v2.10: New BinaryMessage event and SendBinary method.
v2.01: Fixes an issue with ssl disconnections that can throw the network on main thread exception.

v2.00: Based on the latest version of autobahn-java: https://github.com/crossbario/autobahn-java
Adds support for SSL connections (wss://) including using custom trust managers (mainly to accept self signed certificates).
SSL support is problematic on devices prior to Android 5. To support Android 4+ devices you need to update the security provider: https://www.b4x.com/android/forum/threads/ssl-websocket-client.88472/page-2#post-560044
 

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Last edited:

woniol

Active Member
Licensed User
Thanks Erel,
I was waiting for it.

Will it work with b4j?

I have problems running in Release mode. I doesn't connect.
Works fine in Debug mode.
 
Last edited:

woniol

Active Member
Licensed User
When I run it i Debug mode and the server side is not running I get this in log while trying to connect:

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4876)
at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:980)
at android.view.ViewGroup.invalidateChild(ViewGroup.java:4127)
at android.view.View.invalidate(View.java:10328)
at android.view.View.invalidate(View.java:10283)
at android.widget.TextView.checkForRelayout(TextView.java:6601)
at android.widget.TextView.setText(TextView.java:3727)
at android.widget.TextView.setText(TextView.java:3585)
at android.widget.TextView.setText(TextView.java:3560)
at anywheresoftware.b4a.objects.TextViewWrapper.setText(TextViewWrapper.java:39)
at b4a.example.main._updatestatus(main.java:492)
at b4a.example.main._wsh_closed(main.java:519)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:121)
at android.app.Dialog.<init>(Dialog.java:107)
at android.app.AlertDialog.<init>(AlertDialog.java:114)
at android.app.AlertDialog.<init>(AlertDialog.java:98)
at android.app.ProgressDialog.<init>(ProgressDialog.java:77)
at anywheresoftware.b4a.debug.Debug.wait(Debug.java:195)
at anywheresoftware.b4a.debug.Debug.reachBP(Debug.java:260)
at anywheresoftware.b4a.debug.Debug.ErrorCaught(Debug.java:145)
at b4a.example.main._updatestatus(main.java:505)
at b4a.example.main._wsh_closed(main.java:519)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
java.lang.RuntimeException: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:871)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:121)
at android.app.Dialog.<init>(Dialog.java:107)
at android.app.AlertDialog.<init>(AlertDialog.java:114)
at android.app.AlertDialog$Builder.create(AlertDialog.java:913)
at anywheresoftware.b4a.BA.ShowErrorMsgbox(BA.java:221)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:201)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
... 10 more
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
 

woniol

Active Member
Licensed User
Ok,
After adding
B4X:
AddPermission(android.permission.INTERNET)
to the Manifest it works fine in Release
 

MaFu

Well-Known Member
Licensed User
I tried the sample app: compiling with Debug (legacy) settings and running in emulator (Nexus 4 AVD).
But on connect the following error log occurs:
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.


at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4609)
at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:867)
at android.view.ViewGroup.invalidateChild(ViewGroup.java:4066)
at android.view.View.invalidate(View.java:10250)
at android.view.View.invalidate(View.java:10205)
at android.widget.TextView.checkForRelayout(TextView.java:6288)
at android.widget.TextView.setText(TextView.java:3547)
at android.widget.TextView.setText(TextView.java:3405)
at android.widget.TextView.setText(TextView.java:3380)
at anywheresoftware.b4a.objects.TextViewWrapper.setText(TextViewWrapper.java:39)
at b4a.example.main._updatestatus(main.java:489)
at b4a.example.main._wsh_closed(main.java:516)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)


at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.


at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4609)
at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:835)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.view.View.requestLayout(View.java:15129)
at android.widget.TextView.checkForRelayout(TextView.java:6303)
at android.widget.TextView.setText(TextView.java:3547)
at android.widget.TextView.setText(TextView.java:3405)
at android.widget.TextView.setText(TextView.java:3380)


at android.app.ProgressDialog.setMessage(ProgressDialog.java:316)
at anywheresoftware.b4a.debug.Debug.wait(Debug.java:208)
at anywheresoftware.b4a.debug.Debug.reachBP(Debug.java:260)
at anywheresoftware.b4a.debug.Debug.ErrorCaught(Debug.java:145)
at b4a.example.main._updatestatus(main.java:502)
at b4a.example.main._wsh_closed(main.java:516)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.


java.lang.RuntimeException: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()


at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:871)
at anywheresoftware.b4a.keywords.Common.CallSubNew2(Common.java:815)
at b4a.example.websockethandler._ws_closed(websockethandler.java:166)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:174)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:158)
at anywheresoftware.b4a.objects.WebSocketWrapper$1.onClose(WebSocketWrapper.java:60)
at de.tavendo.autobahn.WebSocketConnection.onClose(WebSocketConnection.java:366)
at de.tavendo.autobahn.WebSocketConnection.access$2(WebSocketConnection.java:352)
at de.tavendo.autobahn.WebSocketConnection$WebSocketConnector.run(WebSocketConnection.java:94)
Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:121)
at android.app.Dialog.<init>(Dialog.java:107)
at android.app.AlertDialog.<init>(AlertDialog.java:114)
at android.app.AlertDialog$Builder.create(AlertDialog.java:913)
at anywheresoftware.b4a.BA.ShowErrorMsgbox(BA.java:221)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:201)
at anywheresoftware.b4a.keywords.Common.CallSub4(Common.java:858)
... 10 more
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
 

bluedude

Well-Known Member
Licensed User
I guess the biggest benefit would actually be that it would run with things like Socket.io, PubNub etc. Not tested it, maybe it works.
 

wl

Well-Known Member
Licensed User
Hi Erel,

Is there some kind of heartbeat, so that when the connection drops (tend to occur every once and a while on a mobile device :) this can be detected and a new connection initiated ?

Thanks
 

Douglas Farias

Expert
Licensed User
erel i have this error when i try load the sample server
Program started.
2014-07-16 08:38:52.683:INFO::main: Logging initialized @561ms
2014-07-16 08:38:52.759:INFO:eek:ejs.Server:main: jetty-9.1.z-SNAPSHOT
2014-07-16 08:38:52.778:WARN:eek:ejh.MimeTypes:main: java.util.MissingResourceException: Can't find bundle for base name org/eclipse/jetty/http/encoding, locale pt_BR
2014-07-16 08:38:52.802:INFO:eek:ejsh.ContextHandler:main: Started o.e.j.s.ServletContextHandler@c42916{/,file:/C:/Users/Douglas/Desktop/B4A-WebSocket/Objects/www,AVAILABLE}
2014-07-16 08:38:52.804:INFO:eek:ejs.AbstractNCSARequestLog:main: Opened C:\Users\Douglas\Desktop\B4A-WebSocket\Objects\logs\b4j-2014_07_16.request.log
2014-07-16 08:38:52.821:INFO:eek:ejs.ServerConnector:main: Started ServerConnector@16995df{HTTP/1.1}{0.0.0.0:51042}
2014-07-16 08:38:52.822:INFO:eek:ejs.Server:main: Started @721ms
Emulated network latency: 100ms
 

LucaMs

Expert
Licensed User
I get a strange behavior.

The server (b4j) runs some routines on the client (device) in the right way.
For example:
B4X:
ws.RunFunction("RaisedByServer_NewNickOK", Array As Object(Nick))
ws.Flush

In the case in which the routine is not present in the client code, I rightly get an error.

Only in one of these calls, the routine of the client does not run and I do not get error messages.

The method of the call is identical and also the modules are the same!

SERVER - wshPlayer
B4X:
Private Sub RunOnClient_NewNickOK(Nick As String)  '  <---- THIS IS OK
    ws.RunFunction("RaisedByServer_NewNickOK", Array As Object(Nick))
    ws.Flush
End Sub

Public Sub RunOnClient_PlayerJoinsRoom(msg As String)
Log("RunOnClient_PlayerJoinsRoom") ' <--- I get this log
    ws.RunFunction("RaisedByServer_PlayerJoinsRoom", Array As Object(msg))
    ws.Flush
End Sub

CLIENT - PlayerHandler
B4X:
Public Sub RaisedByServer_NewNickOK(Params As List)  ' <---- THIS IS OK, RUNS
    Private Nick As String = Params.Get(0)
    CallSubDelayed2(CallBack, EventName & "_NewNickOK", Nick)
End Sub

Public Sub RaisedByServer_PlayerJoinsRoom(params As List)
Log("RaisedByServer_PlayerJoinsRoom") ' <--- I DON'T get this log
End Sub

I realize that this explanation is poor; on the other hand I can not post both projects.


I hope this has happened to you :)
 
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