vb.net 检查FTP是否在线/离线
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Check if FTP is online/offline
提问by Janno
What is the best way to determine if a ftp server is online or offline in Visual Basic? I have tried many different ways of pinging the ftp server, but whatever I try, I get this error:
在 Visual Basic 中确定 ftp 服务器是联机还是脱机的最佳方法是什么？我尝试了许多不同的方法来 ping ftp 服务器，但是无论我尝试什么，我都会收到此错误：
An exception occurred during a Ping request.
Is this easily fixable? Or is there a better method than what I'm using?
这很容易修复吗？或者有没有比我正在使用的方法更好的方法？
采纳答案by Don Thomas Boyle
Using webrequest, try this code i found
使用 webrequest，试试我发现的这段代码
Hi, this should work fine:
嗨，这应该可以正常工作：
Imports System.Net
Dim request = _
DirectCast(WebRequest.Create _
("ftp://ftp.example.com/folder_here/"), FtpWebRequest)
request.Credentials = _
New NetworkCredential("user_here", "pass_here")
request.Method = WebRequestMethods.Ftp.ListDirectory
Try
Using response As FtpWebResponse = _
DirectCast(request.GetResponse(), FtpWebResponse)
' Folder exists here
MsgBox("exists!")
End Using
Catch ex As WebException
Dim response As FtpWebResponse = _
DirectCast(ex.Response, FtpWebResponse)
'Does not exist
If response.StatusCode = _
FtpStatusCode.ActionNotTakenFileUnavailable Then
MsgBox("Doesn't exist!")
End If
End Try
..the idea is that we use FtpWebRequest class and pass the folder name with a trailing slash "/", if the folder is found then the response will be processed fine inside Try-Catch block, if the folder could not be found, we handle the exception controlling with statusCode (ActionNotTakenFileUnavailable) to determine if absence of folder causes exception. That should work fine.
..这个想法是我们使用 FtpWebRequest 类并使用尾部斜杠“/”传递文件夹名称，如果找到文件夹，那么响应将在 Try-Catch 块内被很好地处理，如果找不到文件夹，我们使用 statusCode (ActionNotTakenFileUnavailable) 处理异常控制以确定文件夹的缺失是否导致异常。那应该可以正常工作。
--------------- Please also Try----------------------
---------------请也试试--------------
Public Function CheckIfFtpFileExists(ByVal fileUri As String) As Boolean
Dim request As FtpWebRequest = WebRequest.Create(fileUri)
request.Credentials = New NetworkCredential("username", "password")
request.Method = WebRequestMethods.Ftp.GetFileSize
Try
Dim response As FtpWebResponse = request.GetResponse()
' THE FILE EXISTS
Catch ex As WebException
Dim response As FtpWebResponse = ex.Response
If FtpStatusCode.ActionNotTakenFileUnavailable = response.StatusCode Then
' THE FILE DOES NOT EXIST
Return False
End If
End Try
Return True
End Function
Get's called like this:
Get 是这样调用的：
If CheckIfFtpFileExists("ftp://ftp.domain.com/filename.txt") Then
' Do something
End If
回答by PaulG
can you not just do this:
你能不能不这样做：
If My.Computer.Network.Ping("IP HERE") Then
' Success
Else
'fail
End If
Thanks
谢谢
Paul
保罗
回答by Steven Liekens
Typically you write your code in a way that assumes that everything is perfect, then add error handling for cases where the connection fails.
通常，您以假设一切都完美的方式编写代码，然后为连接失败的情况添加错误处理。
Verifying whether the server is online beforehand does not guarantee that it will stay that way for the duration of the user session.
事先验证服务器是否在线并不能保证它会在用户会话期间保持在线状态。
回答by user1838061
- (void)newBuddyOnline:(NSString *)buddyName {
[onlineBuddies addObject:buddyName];
[self.TableView reloadData];
}
- (void)buddyWentOffline:(NSString *)buddyName {
[onlineBuddies removeObje`
`ct:buddyName];
[self.TableView reloadData];
}
This may helps .
这可能会有所帮助。
