| Prerequisites |
| Established network connection or personal web server/IIS. |
|
 The
Win32 API provides a distinct set of functions for connecting to, enumerating and downloading from the Internet. Some are specific to the
connection protocol, ie FTP or Gopher, while others share a commonality making them useful across the range of connections options.
This page presents one method of avoiding the VB Inet control in an
application where the desire is to retrieve/list the files at a target FTP site. Subsequent pages will demonstrate downloading and other
advanced techniques. This demo is not designed to perform as a perfect FTP client, but rather, through copious commenting, attempt to
indicate the procedure for establishing the internet connection, obtaining the connection handles, and iterating through the FTP site's
contents.
An added bonus is demonstration of using the MSDN-provided
TranslateErrorCode function named (GetErr in this demo to reduce line
length). Since the GetLastError API most often can not be used for internet errors, this function translates the errors
into a string. I added the API method InternetGetLastResponseInfo, which returns the meaning of extended error messages returned from Err.LastDllError. |
|
| BAS
Module Code |
|
| Place the following code into the general declarations
area of a bas module: |
|
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Public Const MAX_PATH As Long = 260
Public Const FILE_ATTRIBUTE_ARCHIVE = &H20
'use registry configuration
Public Const INTERNET_OPEN_TYPE_PRECONFIG = 0
'direct to net
Public Const INTERNET_OPEN_TYPE_DIRECT = 1
'via named proxy
Public Const INTERNET_OPEN_TYPE_PROXY = 3
'prevent using java/script/INS
Public Const INTERNET_OPEN_TYPE_PRECONFIG_WITH_NO_AUTOPROXY = 4
'used for FTP connections
Public Const INTERNET_FLAG_PASSIVE = &H8000000
Public Const INTERNET_FLAG_RELOAD = &H80000000
'additional cache flags
'don't write this item to the cache
Public Const INTERNET_FLAG_NO_CACHE_WRITE = &H4000000
Public Const INTERNET_FLAG_DONT_CACHE = INTERNET_FLAG_NO_CACHE_WRITE
'make this item persistent in cache
Public Const INTERNET_FLAG_MAKE_PERSISTENT = &H2000000
'use offline semantics
Public Const INTERNET_FLAG_FROM_CACHE = &H1000000
Public Const INTERNET_FLAG_OFFLINE = INTERNET_FLAG_FROM_CACHE
'additional flags
'use PCT/SSL if applicable (HTTP)
Public Const INTERNET_FLAG_SECURE = &H800000
'use keep-alive semantics
Public Const INTERNET_FLAG_KEEP_CONNECTION = &H400000
'don't handle redirections automatically
Public Const INTERNET_FLAG_NO_AUTO_REDIRECT = &H200000
'do background read prefetch
Public Const INTERNET_FLAG_READ_PREFETCH = &H100000
'no automatic cookie handling
Public Const INTERNET_FLAG_NO_COOKIES = &H80000
'no automatic authentication handling
Public Const INTERNET_FLAG_NO_AUTH = &H40000
'return cache file if net request fails
Public Const INTERNET_FLAG_CACHE_IF_NET_FAIL = &H10000
'return cache file if net request fails
Public Const INTERNET_DEFAULT_FTP_PORT = 21
' " " gopher "
Public Const INTERNET_DEFAULT_GOPHER_PORT = 70
' " " HTTP "
Public Const INTERNET_DEFAULT_HTTP_PORT = 80
' " " HTTPS "
Public Const INTERNET_DEFAULT_HTTPS_PORT = 443
'default for SOCKS firewall servers.
Public Const INTERNET_DEFAULT_SOCKS_PORT = 1080
'FTP: use existing InternetConnect handle for server if possible
Public Const INTERNET_FLAG_EXISTING_CONNECT = &H20000000
Public Const INTERNET_SERVICE_FTP = 1
Public Const INTERNET_SERVICE_GOPHER = 2
Public Const INTERNET_SERVICE_HTTP = 3
'transfer flags
Public Const FTP_TRANSFER_TYPE_UNKNOWN = &H0
Public Const FTP_TRANSFER_TYPE_ASCII = &H1
Public Const FTP_TRANSFER_TYPE_BINARY = &H2
Public Const INTERNET_FLAG_TRANSFER_ASCII = FTP_TRANSFER_TYPE_ASCII
Public Const INTERNET_FLAG_TRANSFER_BINARY = FTP_TRANSFER_TYPE_BINARY
Public Const FTP_TRANSFER_TYPE_MASK = (FTP_TRANSFER_TYPE_ASCII Or _
FTP_TRANSFER_TYPE_BINARY)
'internet error flags
Public Const INTERNET_ERROR_BASE = 12000
Public Const ERROR_INTERNET_OUT_OF_HANDLES = (INTERNET_ERROR_BASE + 1)
Public Const ERROR_INTERNET_TIMEOUT = (INTERNET_ERROR_BASE + 2)
Public Const ERROR_INTERNET_EXTENDED_ERROR = (INTERNET_ERROR_BASE + 3)
Public Const ERROR_INTERNET_INTERNAL_ERROR = (INTERNET_ERROR_BASE + 4)
Public Const ERROR_INTERNET_INVALID_URL = (INTERNET_ERROR_BASE + 5)
Public Const ERROR_INTERNET_UNRECOGNIZED_SCHEME = (INTERNET_ERROR_BASE + 6)
Public Const ERROR_INTERNET_NAME_NOT_RESOLVED = (INTERNET_ERROR_BASE + 7)
Public Const ERROR_INTERNET_PROTOCOL_NOT_FOUND = (INTERNET_ERROR_BASE + 8)
Public Const ERROR_INTERNET_INVALID_OPTION = (INTERNET_ERROR_BASE + 9)
Public Const ERROR_INTERNET_BAD_OPTION_LENGTH = (INTERNET_ERROR_BASE + 10)
Public Const ERROR_INTERNET_OPTION_NOT_SETTABLE = (INTERNET_ERROR_BASE + 11)
Public Const ERROR_INTERNET_SHUTDOWN = (INTERNET_ERROR_BASE + 12)
Public Const ERROR_INTERNET_INCORRECT_USER_NAME = (INTERNET_ERROR_BASE + 13)
Public Const ERROR_INTERNET_INCORRECT_PASSWORD = (INTERNET_ERROR_BASE + 14)
Public Const ERROR_INTERNET_LOGIN_FAILURE = (INTERNET_ERROR_BASE + 15)
Public Const ERROR_INTERNET_INVALID_OPERATION = (INTERNET_ERROR_BASE + 16)
Public Const ERROR_INTERNET_OPERATION_CANCELLED = (INTERNET_ERROR_BASE + 17)
Public Const ERROR_INTERNET_INCORRECT_HANDLE_TYPE = (INTERNET_ERROR_BASE + 18)
Public Const ERROR_INTERNET_INCORRECT_HANDLE_STATE = (INTERNET_ERROR_BASE + 19)
Public Const ERROR_INTERNET_NOT_PROXY_REQUEST = (INTERNET_ERROR_BASE + 20)
Public Const ERROR_INTERNET_REGISTRY_VALUE_NOT_FOUND = (INTERNET_ERROR_BASE + 21)
Public Const ERROR_INTERNET_BAD_REGISTRY_PARAMETER = (INTERNET_ERROR_BASE + 22)
Public Const ERROR_INTERNET_NO_DIRECT_ACCESS = (INTERNET_ERROR_BASE + 23)
Public Const ERROR_INTERNET_NO_CONTEXT = (INTERNET_ERROR_BASE + 24)
Public Const ERROR_INTERNET_NO_CALLBACK = (INTERNET_ERROR_BASE + 25)
Public Const ERROR_INTERNET_REQUEST_PENDING = (INTERNET_ERROR_BASE + 26)
Public Const ERROR_INTERNET_INCORRECT_FORMAT = (INTERNET_ERROR_BASE + 27)
Public Const ERROR_INTERNET_ITEM_NOT_FOUND = (INTERNET_ERROR_BASE + 28)
Public Const ERROR_INTERNET_CANNOT_CONNECT = (INTERNET_ERROR_BASE + 29)
Public Const ERROR_INTERNET_CONNECTION_ABORTED = (INTERNET_ERROR_BASE + 30)
Public Const ERROR_INTERNET_CONNECTION_RESET = (INTERNET_ERROR_BASE + 31)
Public Const ERROR_INTERNET_FORCE_RETRY = (INTERNET_ERROR_BASE + 32)
Public Const ERROR_INTERNET_INVALID_PROXY_REQUEST = (INTERNET_ERROR_BASE + 33)
Public Const ERROR_INTERNET_NEED_UI = (INTERNET_ERROR_BASE + 34)
Public Const ERROR_INTERNET_HANDLE_EXISTS = (INTERNET_ERROR_BASE + 36)
Public Const ERROR_INTERNET_SEC_CERT_DATE_INVALID = (INTERNET_ERROR_BASE + 37)
Public Const ERROR_INTERNET_SEC_CERT_CN_INVALID = (INTERNET_ERROR_BASE + 38)
Public Const ERROR_INTERNET_HTTP_TO_HTTPS_ON_REDIR = (INTERNET_ERROR_BASE + 39)
Public Const ERROR_INTERNET_HTTPS_TO_HTTP_ON_REDIR = (INTERNET_ERROR_BASE + 40)
Public Const ERROR_INTERNET_MIXED_SECURITY = (INTERNET_ERROR_BASE + 41)
Public Const ERROR_INTERNET_CHG_POST_IS_NON_SECURE = (INTERNET_ERROR_BASE + 42)
Public Const ERROR_INTERNET_POST_IS_NON_SECURE = (INTERNET_ERROR_BASE + 43)
Public Const ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED = (INTERNET_ERROR_BASE + 44)
Public Const ERROR_INTERNET_INVALID_CA = (INTERNET_ERROR_BASE + 45)
Public Const ERROR_INTERNET_CLIENT_AUTH_NOT_SETUP = (INTERNET_ERROR_BASE + 46)
Public Const ERROR_INTERNET_ASYNC_THREAD_FAILED = (INTERNET_ERROR_BASE + 47)
Public Const ERROR_INTERNET_REDIRECT_SCHEME_CHANGE = (INTERNET_ERROR_BASE + 48)
Public Const ERROR_INTERNET_DIALOG_PENDING = (INTERNET_ERROR_BASE + 49)
Public Const ERROR_INTERNET_RETRY_DIALOG = (INTERNET_ERROR_BASE + 50)
Public Const ERROR_INTERNET_HTTPS_HTTP_SUBMIT_REDIR = (INTERNET_ERROR_BASE + 52)
Public Const ERROR_INTERNET_INSERT_CD-ROM= (INTERNET_ERROR_BASE + 53)
Public Const ERROR_INTERNET_FORTEZZA_LOGIN_NEEDED = (INTERNET_ERROR_BASE + 54)
Public Const ERROR_INTERNET_SEC_CERT_ERRORS = (INTERNET_ERROR_BASE + 55)
Public Const ERROR_INTERNET_SEC_CERT_NO_REV = (INTERNET_ERROR_BASE + 56)
Public Const ERROR_INTERNET_SEC_CERT_REV_FAILED = (INTERNET_ERROR_BASE + 57)
'FTP API errors
Public Const ERROR_FTP_TRANSFER_IN_PROGRESS = (INTERNET_ERROR_BASE + 110)
Public Const ERROR_FTP_DROPPED = (INTERNET_ERROR_BASE + 111)
Public Const ERROR_FTP_NO_PASSIVE_MODE = (INTERNET_ERROR_BASE + 112)
'gopher API errors
Public Const ERROR_GOPHER_PROTOCOL_ERROR = (INTERNET_ERROR_BASE + 130)
Public Const ERROR_GOPHER_NOT_FILE = (INTERNET_ERROR_BASE + 131)
Public Const ERROR_GOPHER_DATA_ERROR = (INTERNET_ERROR_BASE + 132)
Public Const ERROR_GOPHER_END_OF_DATA = (INTERNET_ERROR_BASE + 133)
Public Const ERROR_GOPHER_INVALID_LOCATOR = (INTERNET_ERROR_BASE + 134)
Public Const ERROR_GOPHER_INCORRECT_LOCATOR_TYPE = (INTERNET_ERROR_BASE + 135)
Public Const ERROR_GOPHER_NOT_GOPHER_PLUS = (INTERNET_ERROR_BASE + 136)
Public Const ERROR_GOPHER_ATTRIBUTE_NOT_FOUND = (INTERNET_ERROR_BASE + 137)
Public Const ERROR_GOPHER_UNKNOWN_LOCATOR = (INTERNET_ERROR_BASE + 138)
'HTTP API errors
Public Const ERROR_HTTP_HEADER_NOT_FOUND = (INTERNET_ERROR_BASE + 150)
Public Const ERROR_HTTP_DOWNLEVEL_SERVER = (INTERNET_ERROR_BASE + 151)
Public Const ERROR_HTTP_INVALID_SERVER_RESPONSE = (INTERNET_ERROR_BASE + 152)
Public Const ERROR_HTTP_INVALID_HEADER = (INTERNET_ERROR_BASE + 153)
Public Const ERROR_HTTP_INVALID_QUERY_REQUEST = (INTERNET_ERROR_BASE + 154)
Public Const ERROR_HTTP_HEADER_ALREADY_EXISTS = (INTERNET_ERROR_BASE + 155)
Public Const ERROR_HTTP_REDIRECT_FAILED = (INTERNET_ERROR_BASE + 156)
Public Const ERROR_HTTP_NOT_REDIRECTED = (INTERNET_ERROR_BASE + 160)
Public Const ERROR_HTTP_COOKIE_NEEDS_CONFIRMATION = (INTERNET_ERROR_BASE + 161)
Public Const ERROR_HTTP_COOKIE_DECLINED = (INTERNET_ERROR_BASE + 162)
Public Const ERROR_HTTP_REDIRECT_NEEDS_CONFIRMATION = (INTERNET_ERROR_BASE + 168)
'additional Internet API error codes
Public Const ERROR_INTERNET_SECURITY_CHANNEL_ERROR = (INTERNET_ERROR_BASE + 157)
Public Const ERROR_INTERNET_UNABLE_TO_CACHE_FILE = (INTERNET_ERROR_BASE + 158)
Public Const ERROR_INTERNET_TCPIP_NOT_INSTALLED = (INTERNET_ERROR_BASE + 159)
Public Const ERROR_INTERNET_DISCONNECTED = (INTERNET_ERROR_BASE + 163)
Public Const ERROR_INTERNET_SERVER_UNREACHABLE = (INTERNET_ERROR_BASE + 164)
Public Const ERROR_INTERNET_PROXY_SERVER_UNREACHABLE = (INTERNET_ERROR_BASE + 165)
Public Const ERROR_INTERNET_BAD_AUTO_PROXY_SCRIPT = (INTERNET_ERROR_BASE + 166)
Public Const ERROR_INTERNET_UNABLE_TO_DOWNLOAD_SCRIPT = (INTERNET_ERROR_BASE + 167)
Public Const ERROR_INTERNET_SEC_INVALID_CERT = (INTERNET_ERROR_BASE + 169)
Public Const ERROR_INTERNET_SEC_CERT_REVOKED = (INTERNET_ERROR_BASE + 170)
'InternetAutodial specific errors
Public Const ERROR_INTERNET_FAILED_DUETOSECURITYCHECK = (INTERNET_ERROR_BASE + 171)
Public Const ERROR_INTERNET_NOT_INITIALIZED = (INTERNET_ERROR_BASE + 172)
Public Const ERROR_INTERNET_NEED_MSN_SSPI_PKG = (INTERNET_ERROR_BASE + 173)
Public Const ERROR_INTERNET_LOGIN_FAILURE_DISPLAY_ENTITY_BODY = (INTERNET_ERROR_BASE + 174)
Public Const INTERNET_ERROR_LAST = ERROR_INTERNET_FAILED_DUETOSECURITYCHECK
Public Type FILETIME
dwLowDateTime As Long
dwHighDateTime As Long
End Type
Public Type WIN32_FIND_DATA
dwFileAttributes As Long
ftCreationTime As FILETIME
ftLastAccessTime As FILETIME
ftLastWriteTime As FILETIME
nFileSizeHigh As Long
nFileSizeLow As Long
dwReserved0 As Long
dwReserved1 As Long
cFileName As String * MAX_PATH
cAlternate As String * 14
End Type
Public Declare Function InternetOpen Lib "wininet" _
Alias "InternetOpenA" _
(ByVal lpszAgent As String, _
ByVal dwAccessType As Long, _
ByVal lpszProxyName As String, _
ByVal lpszProxyBypass As String, _
ByVal dwFlags As Long) As Long
Public Declare Function InternetCloseHandle Lib "wininet" _
(ByVal hEnumHandle As Long) As Long
Public Declare Function InternetConnect Lib "wininet" _
Alias "InternetConnectA" _
(ByVal hInternet As Long, _
ByVal lpszServerName As String, _
ByVal nServerPort As Long, _
ByVal lpszUserName As String, _
ByVal lpszPassword As String, _
ByVal dwService As Long, _
ByVal dwFlags As Long, _
ByVal dwContext As Long) As Long
Public Declare Function FtpFindFirstFile Lib "wininet" _
Alias "FtpFindFirstFileA" _
(ByVal hConnect As Long, _
ByVal lpszSearchFile As String, _
lpFindFileData As Any, _
ByVal dwFlags As Long, _
ByVal dwContext As Long) As Long
Public Declare Function InternetFindNextFile Lib "wininet" _
Alias "InternetFindNextFileA" _
(ByVal hFind As Long, _
lpFindFileData As WIN32_FIND_DATA) As Long
Public Declare Function InternetGetLastResponseInfo Lib "wininet" _
Alias "InternetGetLastResponseInfoA" _
(lpdwError As Long, _
ByVal lpszBuffer As String, _
lpdwBufferLength As Long) As Long
Public Declare Function FtpGetCurrentDirectory Lib "wininet" _
Alias "FtpGetCurrentDirectoryA" _
(ByVal hConnect As Long, _
ByVal lpszCurrentDirectory As String, _
lpdwCurrentDirectory As Long) As Long
Public Declare Function FtpSetCurrentDirectory Lib "wininet" _
Alias "FtpSetCurrentDirectoryA" _
(ByVal hConnect As Long, _
ByVal lpszDirectory As String) As Long
Public Function GetErr(ByVal lErrorCode As Long) As String
'''''''''''''''''''''''''''''''''''''''''''''''''''''
' From : MSDN
' Name : GetErr (Formerly TranslateErrorCode)
' Purpose : Provides message for DLL error codes
' Parameters : The DLL error code
' Return val : String containing message
' Algorithm : Selects the appropriate string
''''''''''''''''''''''''''''''''''''''''''''''''''''''
Dim sBuffer As String
Dim nBuffer As Long
Select Case lErrorCode
Case 12001: GetErr = _
"No more handles could be generated at this time"
Case 12002: GetErr = _
"The request has timed out."
Case 12003:
'extended error. Retrieve the details using
'the InternetGetLastResponseInfo API.
sBuffer = Space$(MAX_PATH)
nBuffer = Len(sBuffer)
If InternetGetLastResponseInfo(lErrorCode, _
sBuffer, _
nBuffer) Then
GetErr = StripNull(sBuffer)
Else
GetErr = "Extended error returned from server."
End If
Case 12004: GetErr = _
"An internal error has occurred."
Case 12005: GetErr = _
"URL is invalid."
Case 12006: GetErr = _
"URL scheme could not be recognized, or is not supported."
Case 12007: GetErr = _
"Server name could not be resolved."
Case 12008: GetErr = _
"Requested protocol could not be located."
Case 12009: GetErr = _
"Request to InternetQueryOption or InternetSetOption" & _
" specified an invalid option value."
Case 12010: GetErr = _
"Length of an option supplied to InternetQueryOption or" & _
" InternetSetOption is incorrect for the type of" & _
" option specified."
Case 12011: GetErr = _
"Request option can not be set, only queried. "
Case 12012: GetErr = _
"Win32 Internet support is being shutdown or unloaded."
Case 12013: GetErr = _
"Request to connect and login to an FTP server could not" & _
" be completed because the supplied user name is incorrect."
Case 12014: GetErr = _
"Request to connect and login to an FTP server could not" & _
" be completed because the supplied password is incorrect. "
Case 12015: GetErr = _
"Request to connect to and login to an FTP server failed."
Case 12016: GetErr = _
"Requested operation is invalid. "
Case 12017: GetErr = _
"Operation was canceled, usually because the handle on" & _
" which the request was operating was closed before the" & _
" operation completed."
Case 12018: GetErr = _
"Type of handle supplied is incorrect for this operation."
Case 12019: GetErr = _
"Requested operation can not be carried out because the" & _
" handle supplied is not in the correct state."
Case 12020: GetErr = _
"Request can not be made via a proxy."
Case 12021: GetErr = _
"Required registry value could not be located. "
Case 12022: GetErr = _
"Required registry value was located but is an incorrect" & _
" type or has an invalid value."
Case 12023: GetErr = _
"Direct network access cannot be made at this time. "
Case 12024: GetErr = _
"Asynchronous request could not be made because a zero" & _
" context value was supplied."
Case 12025: GetErr = _
"Asynchronous request could not be made because a" & _
" callback function has not been set."
Case 12026: GetErr = _
"Required operation could not be completed because" & _
" one or more requests are pending."
Case 12027: GetErr = _
"Format of the request is invalid."
Case 12028: GetErr = _
"Requested item could not be located."
Case 12029: GetErr = _
"Attempt to connect to the server failed."
Case 12030: GetErr = _
"Connection with the server has been terminated."
Case 12031: GetErr = _
"Connection with the server has been reset."
Case 12036: GetErr = _
"Request failed because the handle already exists."
Case Else: GetErr = _
"Error details not available."
End Select
End Function
Function StripNull(item As String)
'Return a string without the chr$(0) terminator.
Dim pos As Integer
pos = InStr(item, Chr$(0))
If pos Then
StripNull = Left$(item, pos - 1)
Else
StripNull = item
End If
End Function |
|
| Form
Code |
|
| Controls listed are from the form top down: To a new form
add two labels for the handles (Label2/Label3), a combo (Combo1), one text box to reflect the FTP path (Text1), a list (List1, and a second
text box for messages (Text2). There are four command buttons named Command1-Command4, one of which is not used here - see the FTP Download
demo for its code. Add the following to the form: |
|
Option Explicit 'persistent handle to the internet
Private hInternet As Long
'persistent handle internet connection
Private hConnect As Long
'default FTP login data
Private Const sFtpUserName = "anonymous"
Private Const sFtpPassword = "yourname@someplace.com"
'constants are more efficient than literals
'when used in several places
Private Const sRootDots = ".."
Private Const sSlash = "/"
Private Sub Command1_Click()
Dim sServerName As String
'Show the wait cursor
Screen.MousePointer = vbHourglass
'Begin the FTP process by obtaining a
'handle to an internet session. This
'handle will be used in subsequent calls,
'so it is declared as a form-wide variable.
hInternet = InternetOpen("VBnet FTP Transfer", _
INTERNET_OPEN_TYPE_DIRECT, _
vbNullString, _
vbNullString, _
INTERNET_FLAG_NO_CACHE_WRITE)
'If a handle was obtained, the next step is
'to obtain a connection handle that will be
'used for all operations except the FTP
'directory navigation. The MSDN states that
'the handle used by FtpFindFirstFile and subsequent
'file calls can not be reused for additional
'navigation or other operations. This handle
'then will be used for all functions except
'the directory listings.
If hInternet Then
sServerName = Combo1.Text
'and get a connection handle
hConnect = InternetConnect(hInternet, _
sServerName, _
INTERNET_DEFAULT_FTP_PORT, _
sFtpUserName, _
sFtpPassword, _
INTERNET_SERVICE_FTP, _
INTERNET_FLAG_EXISTING_CONNECT Or _
INTERNET_FLAG_PASSIVE, _
&H0)
'if the connection handle is valid, get
'the current FTP directory
If hConnect <> 0 Then
'reflect the current path in the
'text box (it should be '\' )
Text1.Text = GetFTPDirectory(hConnect)
Else
'show the error
Text2.Text = GetErr(Err.LastDllError)
End If
End If
'display the session handles
Label3.Caption = hConnect
Label2.Caption = hInternet
'If both handles are valid, disable the Open button
'and enable the FTP button. If *either* handle is
'valid, enable the close button.
Command1.Enabled = (hInternet = 0) And (hConnect = 0)
Command2.Enabled = (hInternet <> 0) And (hConnect <> 0)
Command3.Enabled = (hInternet <> 0) Or (hConnect <> 0)
Command4.Enabled = False
Screen.MousePointer = vbDefault
End Sub
Private Sub Command2_Click()
Call GetFTPDirectoryContents
End Sub
Private Sub Command3_Click()
'clean up
Call InternetCloseHandle(hConnect)
Call InternetCloseHandle(hInternet)
hInternet = 0
hConnect = 0
Label2.Caption = "Closed"
Label3.Caption = "No connection"
'If both handles are valid, enable the Open button
'and disable the FTP button. If *either* handle is
'valid, disable the close button. The download
'button is disabled.
Command1.Enabled = (hInternet = 0) And (hConnect = 0)
Command2.Enabled = (hInternet <> 0) And (hConnect <> 0)
Command3.Enabled = (hInternet <> 0) Or (hConnect <> 0)
Command4.Enabled = False
List1.Clear
End Sub
Private Sub Form_Load()
Label2.Caption = "Closed"
Label3.Caption = "No connection"
Text1.Text = ""
Text2.Text = ""
Command1.Caption = "Open"
Command2.Caption = "FtpFindFirstFile"
Command3.Caption = "Close"
Command4.Caption = "Not used yet"
Command2.Enabled = True
Command2.Enabled = False
Command3.Enabled = False
Command4.Enabled = False
With Combo1
.AddItem "127.0.0.1"'localhost
.AddItem "ftp.microsoft.com"
.AddItem "www.technolog.fr"
.AddItem "www.winfiles.com"
.AddItem "olivo.mentor.mec.es"
.AddItem "main.amu.edu.pl"
.AddItem "tucows.com" 'demonstrates error
.ListIndex = 0
End With
End Sub
Private Sub Form_Unload(Cancel As Integer)
'if the handle is still valid,
'clean up before exiting
If hInternet Or hConnect Then Command3.Value = True
End Sub
Private Sub List1_DblClick()
Dim sNewPath As String
Dim sPath As String
'get the desired directory from the list
sNewPath = List1.List(List1.ListIndex)
'If a root item selected, exit; the routine
'will navigate a level higher. If it is
'a file, we don't want to navigate.
If sNewPath <> sRootDots And Right$(sNewPath, 1) <> sSlash Then
'root or file selected
Exit Sub
Else
'Show the wait cursor
Screen.MousePointer = vbHourglass
'clear the list in preparation for
'retrieving the directory contents
List1.Clear
'retrieve the current FTP path
'using GetFTPDirectory
sPath = GetFTPDirectory(hConnect)
'qualify it if necessary, and append
'the new path to it
If Right$(sPath, 1) <> sSlash Then
sPath = sPath & sSlash & sNewPath
Else
sPath = sPath & sNewPath
End If
'set the new path using the API
Call FtpSetCurrentDirectory(hConnect, sPath)
'reflect the new path in the text box
Text1.Text = GetFTPDirectory(hConnect)
'reload the list with the current directory
GetFTPDirectoryContents
Screen.MousePointer = vbDefault
End If
End Sub
Private Function GetFTPDirectory(hConnect As Long) As String
Dim nCurrDir As Long
Dim sCurrDir As String
'FtpGetCurrentDirectory retrieves the current
'directory for the connection. Using this API
'means its not necessary to track the directory
'hierarchy for navigation.
'pad the requisite buffer
sCurrDir = Space$(MAX_PATH)
nCurrDir = Len(sCurrDir)
'returns 1 if successful
If FtpGetCurrentDirectory(hConnect, sCurrDir, nCurrDir) = 1 Then
'return a properly qualified path
sCurrDir = StripNull(sCurrDir)
If Right$(sCurrDir, 1) <> sSlash Then
GetFTPDirectory = sCurrDir & sSlash
Else
GetFTPDirectory = sCurrDir
End If
End If
End Function
Private Sub GetFTPDirectoryContents()
Dim WFD As WIN32_FIND_DATA
Dim sPath As String
Dim hFindConnect As Long
Dim hFind As Long
Dim sFileSize As String
Dim tmp As String
'Show the wait cursor
Screen.MousePointer = vbHourglass
'Obtain the current FTP path
sPath = GetFTPDirectory(hConnect)
'If the path is not the FTP base directory,
'add ".." to provide a means of navigating
'back up the directory structure. (Note: I added this
'for use on a localhost test - in testing on some
'sites I found that they returned '.' and '..' as
'folders, so ideally a check would want to be made
'in the GetFolders method to avoid loading duplicates.)
If sPath <> sSlash Then List1.AddItem sRootDots
'The search parameters .. here we'll list
'all file types. Since GetFTPDirectory takes
'care of qualifying the path, no terminating
'slash is required.
sPath = sPath & "*.*"
'Conation handles used by the FtpFindFirstFile
'API go out of scope once the all files are
'listed, therefore it can not be reused.
'This restriction is handled by obtaining
'a fresh connection handle each time a call
'to FtpFindFirstFile is required, and releasing
'it once finished.
hFindConnect = GetInternetConnectHandle()
'If a good connection handle ...
If hFindConnect Then
'..obtain the handle to the files with
'the FtpFindFirstFile API. Obtaining the
'directory contents is essentially similar
'to using the Win32 file system APIs
'FindFirstFile and FindNextFile, with the
'sole exception that there is no FtpFindNextFile
'API. Instead, successive calls are made
'to InternetFindNextFile. The data returned
'is in the familiar WIN32_FIND_DATA structure.
hFind = FtpFindFirstFile(hFindConnect, _
sPath, WFD, _
INTERNET_FLAG_RELOAD Or _
INTERNET_FLAG_NO_CACHE_WRITE, 0&)
'If a valid find handle returned,
'loop through the directory listing
'the contents. If the attributes of
'the returned string indicate a folder,
'append a slash to make it both visually
'stand out in the list, and identifiable
'in the list double-click routine for
'navigation.
'
'hFile will be 0 if the navigated-to
'folder is empty.
If hFind Then
Do
tmp = StripNull(WFD.cFileName)
If Len(tmp) Then
If WFD.dwFileAttributes And vbDirectory Then
List1.AddItem tmp & sSlash
Else: List1.AddItem tmp
End If
End If
'continue while valid
Loop While InternetFindNextFile(hFind, WFD)
End If 'If hFind
End If 'If hFindConnect
'clean up by closing the handles used in this routine
Call InternetCloseHandle(hFind)
Call InternetCloseHandle(hFindConnect)
Screen.MousePointer = vbDefault
End Sub
Private Function GetInternetConnectHandle() As Long
Dim sServerName As String
Dim tmp As Long
'GetInternetConnectHandle obtains a new
'handle expressly for use with the
'FtpFindFirstFile and APIs.
'
'Care must be taken to close only the handle
'returned by this function once the listing
'of the directory has been obtained.
'
'A temporary variable is used here
'to reduce line length
If hInternet Then
'Pass the same server as with other
'calls, along with the requisite username
'and password. The Microsoft FTP site
'allows anonymous login, so the username
'is 'anonymous' and the password is the
'user's email address.
sServerName = Combo1.Text
tmp = InternetConnect(hInternet, _
sServerName, _
INTERNET_DEFAULT_FTP_PORT, _
sFtpUserName, _
sFtpPassword, _
INTERNET_SERVICE_FTP, _
INTERNET_FLAG_EXISTING_CONNECT Or _
INTERNET_FLAG_PASSIVE, _
&H0)
End If
'return the connection handle
GetInternetConnectHandle = tmp
End Function |
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