Internet Programming (HTTP and FTTP)
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MAKE WEB APPLICATION WITHOUT KNOWLEDGE OF CODING? CLICK HERE
The WebBrowser and Internet Transfer Controls facilitate
the development of Internet programs.
The WebBrowser Control
The WebBrowser control provides the functionality of Internet
Explorer through point and click hyperlinks. To use the WebBrowser
Control, add it to the ToolBox by selecting the Components menu
item and select Microsoft Internet Controls from the list. The
use of the control is self-explanitory as can be seen in the following
example.
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Option Explicit
Private Sub cmdBack_Click()
On Error Resume Next
webBrowser.GoBack
End Sub
Private Sub cmdForward_Click()
On Error Resume Next
webBrowser.GoForward
End Sub
Private Sub cmdHome_Click()
On Error Resume Next
webBrowser.GoHome
End Sub
Private Sub cmdRefresh_Click()
On Error Resume Next
webBrowser.Refresh
End Sub
Private Sub cmdStop_Click()
lblStatus.Caption = "Interrupted"
webBrowser.Stop
End Sub
Private Sub Form_Activate()
webBrowser.Width = Me.ScaleWidth
webBrowser.Height = Me.ScaleHeight
- webBrowser.Top
fraNavigation.Width = Me.ScaleWidth
txtURL.Width = Me.ScaleWidth -
txtURL.Left - 500
End Sub
Private Sub Form_Load()
webBrowser.Navigate "https://www.juicystudio.com"
End Sub
Private Sub txtURL_GotFocus()
txtURL.SelStart = 0
txtURL.SelLength = Len(txtURL.Text)
End Sub
Private Sub txtURL_KeyPress(KeyAscii As Integer)
If KeyAscii = 13 Then
KeyAscii
= 0
webBrowser.Navigate
txtURL.Text
End If
End Sub
Private Sub webBrowser_DocumentComplete(ByVal pDisp As Object,
URL As Variant)
txtURL.Text = URL
End Sub
Private Sub webBrowser_DownloadBegin()
lblStatus.Caption = "Loading
..."
End Sub
Private Sub webBrowser_DownloadComplete()
lblStatus.Caption = "Loaded"
End Sub |
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THE INTERNET CONTROL
The Internet Transfer Control supports the Hypertext
Transfer Protocol (HTTP) and File Transfer Protocol (FTP)
networking protocols. To use the Internet Transfer Control,
add it to the ToolBox by selecting the Components menu item and
select Microsoft Internet Transfer Control 6.0 from the list.
Hypertext Transfer Protocol (HTTP)
To retrieve a file using HTTP is simply a case of using
the Internet Transfer Control's OpenURL method. The actual
file is retrieved, rather than the formatted HTML.
The following example has an Internet Transfer control
named itcHTTP and two TextBoxes named txtURL and txtFile. The txtFile's
MultiLine Property is set to True.
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Option Explicit
Private Sub txtFile_GotFocus()
txtURL.SetFocus
End Sub
Private Sub txtURL_KeyPress(KeyAscii As Integer)
If KeyAscii = 13 Then
KeyAscii
= 0
txtFile.Text
= "Downloading file " & txtURL.Text & "..."
On
Error GoTo URLError
txtFile.Text
= itcHTTP.OpenURL(Trim(txtURL.Text))
End If
Exit Sub
URLError:
MsgBox Err.Description, vbExclamation,
"OpenURL"
txtFile.Text = "Unable to
open " & txtURL.Text
txtFile.Text = txtFile.Text &
" - " & Err.Description
End Sub |
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FILE TRANSFER PROTOCOL (FTP)
FTP Commands can be sent through the Internet Transfer
Control's Execute method. The Execute method executes a request
on the remote server. The first parameter specifies the URL, and
the second parameter specifies the operation to be performed. The
URL parameter is optional and if not provided the Internet Transfer
Control's URL property will be used. The GetChunk method
reads the data returned.
The following example requests the current directory and
writes it to a Label called lblRemoteDirectory.
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itcFTP.Execute "ftp.juicystudio.com",
"pwd"
lblRemoteDirectory.Caption = itcFTP.GetChunk(1024, icString) |
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DETERMINING THE FTP STATE:
The StateChanged Event fires when there is a change
in the connection. The Select Case construct can be used to determine
the state and what action to take.
The following example writes the state to a Label called
lblStatus when the StateChanged Event fires.
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Private Sub itcFTP_StateChanged(ByVal
State As Integer)
Select Case State
Case icResolvingHost
lblStatus.Caption
= "Resolving Host"
Case icHostResolved
lblStatus.Caption
= "Host Resolved"
Case icConnecting
lblStatus.Caption
= "Connecting ..."
Case icConnected
lblStatus.Caption
= "Connected"
Case icRequesting
lblStatus.Caption
= "Requesting ..."
Case icRequestSent
lblStatus.Caption
= "Request Sent"
Case icReceivingResponse
lblStatus.Caption
= "Receiving ..."
Case icResponseReceived
lblStatus.Caption
= "Response Received"
Case icDisconnecting
lblStatus.Caption
= "Disconnecting ..."
Case icDisconnected
lblStatus.Caption
= "Disconnected"
Case icError
lblStatus.Caption
= itcFTP.ResponseInfo
Case icResponseCompleted
lblStatus.Caption
= "Operation Complete"
End Select
End Sub |
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FTP PROPERTIES:
The Properties of the Internet Transfer Control may
be used to set up the FTP Remote Address Settings. The
URL, UserName, and Password properties may be used to
set up the remote address.
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itcFTP.URL = txtAddress.Text
itcFTP.UserName = txtUsername.Text
itcFTP.Password = txtPassword.Text |
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The execute command will use the URL property if the parameter
for the URL is missing.
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FTP EXAMPLE PROGRAM
The following is a fully working FTP program that uses the Internet
Transfer Control.
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Option Explicit
Private Sub cmdConnect_Click()
' Use the caption property to
determine whether to connect or disconnect
If Left(cmdConnect.Caption, 4)
= "&Con" Then
connectHost
Else
disconnectHost
End If
End Sub
Private Sub cmdDelete_Click()
Dim strOperation As String
Dim strFilename As String
Dim response As Integer, counter
As Integer
response = MsgBox("Are you
sure", vbQuestion + vbYesNo, "Delete")
If response = vbYes Then
For
counter = 0 To lstRemote.ListCount - 1
If
lstRemote.Selected(counter) = True Then
strFilename
= lstRemote.List(counter)
'
Determine whether directory or file
If
Right(strFilename, 1) = "/" Then
strOperation
= "rmdir " & Left(strFilename, Len(strFilename)
- 1)
Else
strOperation
= "delete " & strFilename
End
If
executeCommand
strOperation, False
End
If
Next
counter
listDir
End If
End Sub
Private Sub cmdMkDir_Click()
Dim dir As String, strOperation
As String
dir = InputBox("Enter directory
name", "Make Directory")
If dir <> "" Then
strOperation
= "mkdir " & dir
executeCommand
strOperation, True
End If
End Sub
Private Sub cmdReceive_Click()
Dim counter As Integer
Dim strOperation As String
Dim strFilename As String, outFile
As String
For counter = 0 To lstRemote.ListCount
- 1
If
lstRemote.Selected(counter) = True Then
strFilename
= lstRemote.List(counter)
If
Len(dirList.Path) > 3 Then
outFile
= dirList.Path & "\" & strFilename
Else
outFile
= dirList.Path & strFilename
End
If
strOperation
= "recv " & strFilename & " " &
outFile
executeCommand
strOperation, False
lstRemote.Selected(counter)
= False
End
If
Next counter
filList.Refresh
End Sub
Private Sub cmdSend_Click()
Dim counter As Integer
Dim strOperation As String
Dim strFilename As String, outFile
As String
For counter = 0 To filList.ListCount
- 1
If
filList.Selected(counter) = True Then
strFilename
= filList.List(counter)
outFile
= lblRemoteDirectory.Caption & "/" & strFilename
strOperation
= "send " & strFilename & " " &
outFile
executeCommand
strOperation, False
End
If
Next counter
listDir
filList.Refresh
End Sub
Private Sub dirList_Change()
filList.Path = dirList.Path
End Sub
Private Sub drvList_Change()
On Error GoTo driveError
dirList.Path
= drvList.Drive
Exit
Sub
driveError:
MsgBox Err.Description, vbExclamation,
"Drive Error"
End Sub
Private Sub Form_Unload(Cancel As Integer)
If cmdSend.Enabled = True Then
itcFTP.Execute
, "quit"
End If
End Sub
Private Sub itcFTP_StateChanged(ByVal State As Integer)
Select Case State
Case
icResolvingHost
lblStatus.Caption
= "Resolving Host"
Case
icHostResolved
lblStatus.Caption
= "Host Resolved"
Case
icConnecting
lblStatus.Caption
= "Connecting ..."
Case
icConnected
lblStatus.Caption
= "Connected"
Case
icRequesting
lblStatus.Caption
= "Requesting ..."
Case
icRequestSent
lblStatus.Caption
= "Request Sent"
Case
icReceivingResponse
lblStatus.Caption
= "Receiving ..."
Case
icResponseReceived
lblStatus.Caption
= "Response Received"
Case
icDisconnecting
lblStatus.Caption
= "Disconnecting ..."
Case
icDisconnected
lblStatus.Caption
= "Disconnected"
Case
icError
lblStatus.Caption
= itcFTP.ResponseInfo
txtLog.Text
= txtLog.Text & itcFTP.ResponseInfo & vbCrLf
Case
icResponseCompleted
lblStatus.Caption
= "strOperation Complete"
txtLog.Text
= txtLog.Text & "Operation Complete" & vbCrLf
End Select
txtLog.SelStart = Len(txtLog.Text)
End Sub
Private Sub lstRemote_DblClick()
Dim strOperation As String, dir
As String
' If item is a directory, change
to that directory
If Right(lstRemote.List(lstRemote.ListIndex),
1) = "/" Then
dir
= lstRemote.List(lstRemote.ListIndex)
strOperation
= "cd " & Left(dir, Len(dir) - 1)
executeCommand
strOperation, True
End If
End Sub
Private Sub txtLog_GotFocus()
txtAddress.SetFocus
End Sub
Private Sub connectHost()
itcFTP.URL = txtAddress.Text
itcFTP.UserName = txtUsername.Text
itcFTP.Password = txtPassword.Text
listDir
cmdSend.Enabled = True
cmdReceive.Enabled = True
cmdMkDir.Enabled = True
cmdDelete.Enabled = True
lstRemote.Enabled = True
cmdConnect.Caption = "D&isconnect
from Remote Host"
Exit Sub
connectError:
MsgBox Err.Description, vbExclamation,
"FTP"
End Sub
Private Sub disconnectHost()
Dim strOperation As String
itcFTP.Execute , "quit"
strOperation = "quit"
executeCommand strOperation, False
cmdSend.Enabled = False
cmdReceive.Enabled = False
cmdMkDir.Enabled = False
cmdDelete.Enabled = False
lstRemote.Enabled = False
cmdConnect.Caption = "&Connect
to Remote Host"
End Sub
Private Sub executeCommand(ByVal op As String, ByVal ld As Boolean)
If itcFTP.StillExecuting Then
itcFTP.Cancel
End If
txtLog.Text = txtLog.Text &
"Command: " & op & vbCrLf
itcFTP.Execute , op
finishCommand
If ld = True Then
listDir
finishCommand
End If
End Sub
Private Sub finishCommand()
Do While itcFTP.StillExecuting
DoEvents
Loop
End Sub
Private Sub listDir()
Dim strOperation As String
Dim data As Variant, counter As
Integer
Dim start As Integer, length As
Integer
start = 1
lstRemote.Clear
strOperation = "dir"
executeCommand strOperation, False
Do
data
= itcFTP.GetChunk(1024, icString)
DoEvents
For
counter = 1 To Len(data)
If
Mid(data, counter, 1) = Chr(13) Then
If
length > 0 And Mid(data, start, length) <> "./"
Then
lstRemote.AddItem
Mid(data, start, length)
End
If
start
= counter + 2
length
= -1
Else
length
= length + 1
End
If
Next
counter
Loop While LenB(data) > 0
strOperation = "pwd"
executeCommand strOperation, False
lblRemoteDirectory.Caption = itcFTP.GetChunk(1024,
icString)
End Sub |
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