Android Question Network problems solved

luke2012 · Aug 25, 2017

This Thread is to say "THANKS" to the @Erel (great) tutorial that helped me to solve a difficult network problem (crash, wrong connection mgmt etc) within my client App (all network core objects and messages was within main).

I'm sharing my experience because I think that this great tutorial could help other (in panic) developers.

THE TUTORIAL
https://www.b4x.com/android/forum/threads/b4x-network-asyncstreams-b4xserializator.72149/

Thanks @Erel

luke2012 · Aug 29, 2017

The network connection code seems to run successfully after a couple of mod that I have done to the original tutorial (sample).

I have only a couple of doubts:

1) Doubt1 - "Disconnect"

Within my App I need to send some data to the target (server) device and just after the send I need to close the connection. Is my code correct ?

B4X:

Public Sub ConnectToServer(Host As String, Buffer As String)

Log("Trying to connect to: " & Host)

CloseExistingConnection

Dim client As Socket

client.Initialize("client")

client.Connect(Host, PORT, 10000)


Wait For Client_Connected (Successful As Boolean)

If Successful Then

astream.InitializePrefix(client.InputStream, False, client.OutputStream, "astream")

UpdateState (True)


'Print & disconnect

PrintBuffer (Buffer)

CallSubDelayed (Me, "Disconnect")


Else


Log("Failed to connect: " & LastException)

LastError = LastException

CallSub2 (Main, "ShowError", PRT1)

EndIf

EndSub

'client & astream events follow (like the Erel tutorial)....

2) Doubt2 - "Connect"
Is my code correct in order to send to 2 servers ?

B4X:

'*** Main

Sub JobDone (Job As HttpJob)

  If Job.JobName = "CheckJob" Then
      CreateBufferAndSend
  End If

End Sub


Private Sub CreateBufferAndSend
  
    Private Buffer4Printer1 As String = "Buffer1..."
    CallSub2 (Me, "send_Click", Buffer4Printer1)

    Private Buffer4Printer2 As String = "Buffer2..."
    CallSub2 (Me, "send1_Click", Buffer4Printer2)

End Sub

Sub send_Click (Buffer As String)

     CallSub2 (Starter, "Connect", Buffer)

End Sub

Sub send1_Click (Buffer1 As String)

      CallSub2 (Starter, "Connect1", Buffer1)

End Sub

'*** Starter

Public Sub Connect (Buffer As String)

       If connected = False Then
           ConnectToServer (IP, Buffer)
       End If

End Sub

Public Sub Connect1 (Buffer As String)

    If connected1 = False Then
       ConnectToServer1 (IP1, Buffer)
    End If

End Sub

Thanks in advance for your reply

Erel · Aug 30, 2017

Note that the extra lines in your code makes it difficult to read the code.

1. Why are you using CallSub to call a sub in the current modules?
2. You haven't posted the code in PrintBuffer. Does it send data with AStream.Write? It is an asynchronous method. Don't close the connection immediately.

B4X:

PrintBuffer(...)
astream.SendAllAndClose
'the Terminated event will be raised when the connection is closed

luke2012 · Aug 31, 2017

Erel said:
Note that the extra lines in your code makes it difficult to read the code.

1. Why are you using CallSub to call a sub in the current modules?
2. You haven't posted the code in PrintBuffer. Does it send data with AStream.Write? It is an asynchronous method. Don't close the connection immediately.

B4X:

PrintBuffer(...) astream.SendAllAndClose 'the Terminated event will be raised when the connection is closed

1. Yes: PrintBuffer calls SendData (Buffer.GetBytes(...)) than astream.Write.
I'm using "CallSubDelayed (Me, "Disconnect")" because I want to ensure that the disconnect sub will be called only after the astream.Write method has finished to send the whole buffer to the target connected device (probably I'm wrong).

CallSubDelayed IDE help says: "The sub will be called when the message is processed. This is useful in cases where you want to do something "right after" the current sub...

So you are telling me that I have to wait for the astream_Teminated event and only within this event I can call "Disconnect" Sub?
Otherwise my posted code (post #2 - 1. Doubt1) could introduce bugs when I send the buffer to the connected target device ?

Instead of astream.Write(data) I have to use astream.SendAllAndClose?

Or I have to call the astream.SendAllAndClose just after the PrintBuffer?
In this case all the PrintBuffer and SendData code remain the same. Correct?

If the second case is correct, which return flag I have to check to ensure that the write was executed successfully (both) ?

StreamWriteOK = astream.Write(data)
StreamWriteOK1 = astream.SendAllAndClose

B4X:

Public Sub SendData (data() As Byte)
          If connected Then
                  StreamWriteOK = astream.Write(data)
                  Log ("StreamWriteOK = " & StreamWriteOK)
          End If
End Sub

Sub PrintBuffer (Buffer As String)
      SendData (Buffer.GetBytes("UTF8"))
End Sub

So the _Teminated event should be ...

B4X:

Sub AStream_Terminated
     UpdateState(False)
     Disconnect
End Sub

Erel · Aug 31, 2017

CallSubDelayed has nothing to do with AsyncStreams. It sends a message to the internal message queue which calls the sub when it is processed. It will happen very quickly.

A simple solution is to wait for a short delay and then call disconnect:

B4X:

AStream.Write(...)
Sleep(200)
Disconnect

Another option is to call AStream.SendAllAndClose which closes the connection for you after all the queued data was sent.

luke2012 · Aug 31, 2017

Erel said:
CallSubDelayed has nothing to do with AsyncStreams. It sends a message to the internal message queue which calls the sub when it is processed. It will happen very quickly.

A simple solution is to wait for a short delay and then call disconnect:

B4X:

AStream.Write(...) Sleep(200) Disconnect

Another option is to call AStream.SendAllAndClose which closes the connection for you after all the queued data was sent.

My target is to implement the most reliable solution to connect, send (data) and disconnect.

So in this case which solution is the most reliable and technical correct between A and B ?

Solution A:

PrintBuffer(...)
astream.SendAllAndClose'the Terminated event will be raised when the connection is closed
.....

B4X:

Public Sub SendData (data() As Byte)
          If connected Then
                  StreamWriteOK = astream.Write(data)
                  Log ("StreamWriteOK = " & StreamWriteOK)
          End If
End Sub

Sub PrintBuffer (Buffer As String)
      SendData (Buffer.GetBytes("UTF8"))
End Sub

So the _Teminated event should be ...

B4X:

Sub AStream_Terminated
     UpdateState(False)
     Disconnect
End Sub

Solution B

B4X:

AStream.Write(...)
Sleep(200)
Disconnect

Thanks in advance for your reply

Erel · Sep 2, 2017

SendAllAndClose should be the preferred method.

Android Question Network problems solved

luke2012

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Erel

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