Android Tutorial Android FTP tutorial

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Erel

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This tutorial covers the FTP object which is part of the Net library.
The Net library is based on Apache Commons Net.

Android OS doesn't allow us, the developers, to block the main thread for more than 5 seconds. When the main thread is busy for too long and is not able to handle the user events the "Application not responding" dialog appears.
Therefore slow operations like network operations should be done in the background.
The FTP library is built in such a way. All of the methods return immediately. When a task completes an event is raised. In fact you can submit several tasks one after another. The FTP protocol supports a single task at a time so the tasks will be processed serially.

Using the FTP library is pretty simple.
The first step is to initialize the FTP object. If this is an Activity module then you should do it in Activity_Create when FirstTime is true.
For Service modules it should be initialized in Service_Create.
B4X:
Sub Process_Globals
    Dim FTP As FTP
End Sub
Sub Globals

End Sub

Sub Activity_Create(FirstTime As Boolean)
    If FirstTime Then
        FTP.Initialize("FTP", "ftp.example.com", 21, "user", "password")
    End If
FTP.Initialize doesn't connect to the server. Connection will be established implicitly together with the next task.

Download

Downloading a file is done by calling DownloadFile with the remote file path and the local file path.
If you want to show the download progress then you should handle DownloadProgress event.
When download completes the DownloadCompleted event is raised. The ServerPath is passed as the first parameter to all events. You can use it to distinguish between different tasks. Make sure to check the Success parameter. If Success is False then you can find the exception message by calling LastException.

B4X:
    FTP.DownloadFile("/somefolder/files/1.zip", False, File.DirRootExternal, "1.zip")
    
Sub FTP_DownloadProgress (ServerPath As String, TotalDownloaded As Long, Total As Long)
    Dim s As String
    s = "Downloaded " & Round(TotalDownloaded / 1000) & "KB"
    If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
    Log(s)
End Sub

Sub FTP_DownloadCompleted (ServerPath As String, Success As Boolean)
    Log(ServerPath & ", Success=" & Success)
    If Success = False Then Log(LastException.Message)
End Sub
Upload

Uploading is similar to downloading.
B4X:
    FTP.UploadFile(File.DirRootExternal, "1.txt", True, "/somefolder/files/1.txt")

Sub FTP_UploadProgress (ServerPath As String, TotalUploaded As Long, Total As Long)
    Dim s As String
    s = "Uploaded " & Round(TotalUploaded / 1000) & "KB"
    If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
    Log(s)
End Sub

Sub FTP_UploadCompleted (ServerPath As String, Success As Boolean)
    Log(ServerPath & ", Success=" & Success)
    If Success = False Then Log(LastException.Message)
End Sub
List files and folders

FTP.List sends a request for the list of files and folders in a specific path.
The ListCompleted event is raised when the data is available.
You can use code similar to the following code to get more information on the entries:
B4X:
FTP.List("/")
...
Sub FTP_ListCompleted (ServerPath As String, Success As Boolean, Folders() As FTPEntry, Files() As FTPEntry)
    Log(ServerPath)
    If Success = False Then
        Log(LastException)
    Else
        For i = 0 To Folders.Length - 1
            Log(Folders(i).Name)
        Next
        For i = 0 To Files.Length - 1
            Log(Files(i).Name & ", " & Files(i).Size & ", " & DateTime.Date(Files(i).Timestamp))
        Next
    End If
End Sub
Delete
Delete is done by calling FTP.Delete with the full path. Again an event will be raised when the task completes (DeleteCompleted).

Closing the connection
You can close the connection by calling FTP.Close. Close will wait for the other tasks to complete and then will close the connection. This happens in the background.
FTP.CloseNow will immediately close the connection, failing the remaining tasks.

Some notes:
- At any given time there should be less than 15 waiting tasks. Otherwise you will get a RejectedExecutionException (this happens when the internal threads pool is exhausted).
- The order of the completed tasks may be different than the order of submission.
- The AsciiFile parameters sets the file transfer mode. If AsciiFile is true then every occurrence of an end of line character will be translated based on the server native end of line character. If your FTP server is Unix or Linux then the end of line character is the same as Android.
In most cases you can set AsciiFile to false.

The library is available for download here: http://www.basic4ppc.com/forum/additional-libraries-classes-official-updates/10892-new-net-library-android-ftp-smtp-pop3.html
 

AscySoft

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Does this library knows sftp protocol? Sorry, this is my first day with android/b4a :D
 

AscySoft

Active Member
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Then I must encode/zip files manually for strong security reason then upload them using ftp! Coud you point to a solution/link that sound anything like that? I mean, zip with password/encode files etc
 

carlosmdg

Member
Licensed User
What error do you get?
I'd like to sync through ftp but not responding.
The code i have is the following:


B4X:
Sub Process_Globals
...
   Dim FTP As FTP
End Sub

B4X:
Sub Activity_Create(FirstTime As Boolean)
   Activity.AddMenuItem2("Sincronizar","update2",LoadBitmap(File.DirAssets,"refresh.png"))
   If FirstTime Then
      FTP.Initialize("FTP", "ftp.xxx", 21, "user", "pass")
   End If
End Sub


B4X:
Sub Update2_click
   sdRoot = File.DirDefaultExternal & "/"
   FTP.DownloadFile("/Team/prestadores.txt", False, sdRoot, "PRESTADORESFTP.txt")
   FTP.UploadFile(sdRoot,"Reg" & d.GetDeviceId  & ".txt", True, "/Team/RegTmp" & d.GetDeviceId  & ".txt")
End Sub
when in using debug mode, i see this:

B4X:
DownloadService [donesuccessfully=false, hc=anywheresoftware.b4a.http.HttpClientWrapper@44d029d0, jobstatus=0 , notification=1(Notification) Not initialized, status_done=2, status_none=0, status_working=1, target=(OutputStream) Not initialized, url=
I test the apk in my dispositive but dont work
 

Erel

Administrator
Staff member
Licensed User
The DownloadService is not related. It is a code module that you have added to your project.

Have you added the FTP_DownloadCompleted / FTP_UploadCompleted subs? Without them you will not see any result.
 

carlosmdg

Member
Licensed User
The DownloadService is not related. It is a code module that you have added to your project.

Have you added the FTP_DownloadCompleted / FTP_UploadCompleted subs? Without them you will not see any result.
I have a Service module called DownloadService, it's the same like the example http://www.basic4ppc.com/forum/basic...#post43109

And I have this subs...

B4X:
Sub FTP_DownloadProgress (ServerPath As String, TotalDownloaded As Long, Total As Long)
    Dim s As String
    s = "Downloaded " & Round(TotalDownloaded / 1000) & "KB"
    If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
    Log(s)
End Sub

Sub FTP_DownloadCompleted (ServerPath As String, Success As Boolean)
    Log(ServerPath & ", Success=" & Success)
    If Success = False Then Log(LastException.Message)
End Sub

Sub FTP_UploadProgress (ServerPath As String, TotalUploaded As Long, Total As Long)
    Dim s As String
    s = "Uploaded " & Round(TotalUploaded / 1000) & "KB"
    If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
    Log(s)
End Sub

Sub FTP_UploadCompleted (ServerPath As String, Success As Boolean)
    Log(ServerPath & ", Success=" & Success)
    If Success = False Then Log(LastException.Message)
End Sub
When i run the project step by step, never calls to DownloadService module
 

Erel

Administrator
Staff member
Licensed User
Try to create a simple project which downloads a single file and see if it works. Make sure to check the logs (including the unfiltered logs if you don't see any message).
 

carlosmdg

Member
Licensed User
Try to create a simple project which downloads a single file and see if it works. Make sure to check the logs (including the unfiltered logs if you don't see any message).
I did this, but the problem persist

I Attach a project.
The DownloadService requires two variables: URL and TARGET, the "TARGET" i do know what is, but the "URL" i don't know because i'm trying to download from FTP instead of URL
What variable must i asign to Download Service.URL ?
 

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Last edited:

Erel

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In order to upload your project you should choose File - Export to zip. The current zip file is missing several files.

DownloadService cannot be used with FTP. It is a way to download files with HTTP.
 

danoptic

Member
Licensed User
I doesnt work for me - here is the code

Sub Process_Globals
Dim FTP As FTP
End Sub
Sub Globals

End Sub

Sub Activity_Create(FirstTime As Boolean)
If FirstTime Then
FTP.Initialize("FTP", "ftp.example.com", 21, "user", "password")

End If
activity.LoadLayout("test")
End Sub



Sub FTP_DownloadProgress (ServerPath As String, TotalDownloaded As Long, Total As Long)
Dim s As String
s = "Downloaded " & Round(TotalDownloaded / 1000) & "KB"
If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
Log(s)
End Sub

Sub FTP_DownloadCompleted (ServerPath As String, Success As Boolean)
Log(ServerPath & ", Success=" & Success)
If Success = False Then Log(LastException.Message)
End Sub


Sub FTP_UploadProgress (ServerPath As String, TotalUploaded As Long, Total As Long)
Dim s As String
s = "Uploaded " & Round(TotalUploaded / 1000) & "KB"
If Total > 0 Then s = s & " out of " & Round(Total / 1000) & "KB"
Log(s)
End Sub

Sub FTP_UploadCompleted (ServerPath As String, Success As Boolean)
Log(ServerPath & ", Success=" & Success)
If Success = False Then Log(LastException.Message)
End Sub
Sub UploadButton_Click
FTP.UploadFile(File.DirRootExternal, "1.jpg", True, "/myandroidapp/1.jpg")
End Sub
Sub DownloadButton_Click
FTP.DownloadFile("/myandroidapp/1.zip", False, File.DirRootExternal, "1.zip")
End Sub


the error messages:

LogCat connected to: 3333B9BC2E5600EC
--------- beginning of /dev/log/main
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
/myandroidapp/1.zip, Success=false
java.lang.RuntimeException: Error retrieving file.
550 /myandroidapp/1.zip: The system cannot find the path specified.
/myandroidapp/1.jpg, Success=false
java.lang.RuntimeException: Error uploading file.
550 /myandroidapp/1.jpg: Access is denied.
 

Erel

Administrator
Staff member
Licensed User
Based on the logs it seems that the path to the server file is not correct.
 

danoptic

Member
Licensed User
explain please

The ftp adress is the sam as i entr in filezilla
the folder is the next folder undr the root
and what aboutt the upload error?
 

Erel

Administrator
Staff member
Licensed User
It is possible that filezilla is configured to start in some default path.
There is an access denied message in the log when you try to upload. This can happen because your user do not have the right permission or that you are trying to upload the the wrong path.
 

Erel

Administrator
Staff member
Licensed User
I ran your program and it seems to run fine.
It download the file and printed this message to the log:
Team/prestadores.txt, Success=true
 

carlosmdg

Member
Licensed User
I ran your program and it seems to run fine.
It download the file and printed this message to the log:
Team/prestadores.txt, Success=true
ja!
I ran the program and when i click on the button the FTP.Downloadfile does nothing. Never enters to FTP_DownloadCompleted

but the FTP.DownloadFile creates the file "PRESTATUTI" without content
 
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