vb.net 教程 4-10 XML文件操作 4-4

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当按下“开始”按钮后设置Timer的时间间隔，同时先检测一次：

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click

If btnStart.Text = "停止" Then

blStopCheck = True

If threadCheck.ThreadState = ThreadState.Running Then threadCheck.Abort()

tmCheck.Stop()

btnStart.Text = "开始"

btnAdd.Enabled = True

btnDel.Enabled = True

comTime.Enabled = True

Exit Sub

End If

blStopCheck = False

If My.Computer.Network.IsAvailable = False Then

tsslInfo.Text = "目前网络中断，请先检查网络"

Exit Sub

End If

If lvCheck.Items.Count < 1 Then

tsslInfo.Text = "没有设置要检查的计算机或网页"

Exit Sub

End If

btnAdd.Enabled = False

btnDel.Enabled = False

comTime.Enabled = True = False

Dim timeInterval As Integer

Select Case comTime.SelectedIndex

Case 0

timeInterval = 1 * 60 * 1000

Case 1

timeInterval = 3 * 60 * 1000

Case 2

timeInterval = 5 * 60 * 1000

Case 3

timeInterval = 10 * 60 * 1000

Case 4

timeInterval = 20 * 60 * 1000

Case 5

timeInterval = 30 * 60 * 1000

Case Else

timeInterval = 60 * 60 * 1000

End Select

tmCheck.Interval = timeInterval

tmCheck.Start()

btnStart.Text = "停止"

Call beginCheck()

End Sub

计时器的事件：

Private Sub tmCheck_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmCheck.Tick

Call beginCheck()

End Sub

检测代码，调用了多线程，实际将调用 checkAddr()方法

Private Sub beginCheck()

writeErrlog("启动检测")

If (threadCheck Is Nothing) Then

threadCheck = New Thread(AddressOf checkAddr)

threadCheck.Start()

Else

'如果检测线程还在运行

If threadCheck.ThreadState = ThreadState.Running Then

Exit Sub

Else

threadCheck = New Thread(AddressOf checkAddr)

threadCheck.Start()

End If

End Sub

实际检测的时候又需要分别按照网络地址或网页地址检测：

Private Sub checkAddr()

If lvCheck.Items.Count < 1 Then Exit Sub

Dim lvAddrInfo As String = ""

Dim lvAddrType As String = ""

Dim checkResult As Boolean = False

For i As Integer = 0 To lvCheck.Items.Count - 1

If blStopCheck = True Then

btnStart.Text = "开始"

Exit Sub

End If

lvAddrInfo = lvCheck.Items(i).SubItems(3).Text

lvAddrType = lvCheck.Items(i).SubItems(2).Text

If lvAddrType.ToLower = "pc" Then

checkResult = getAddrStatePC(lvAddrInfo)

Else

checkResult = getAddrStateWww(lvAddrInfo)

End If

lvCheck.Items(i).UseItemStyleForSubItems = False

If checkResult = True Then

lvCheck.Items(i).SubItems(4).Text = "成功"

lvCheck.Items(i).SubItems(4).ForeColor = Color.Black

Else

lvCheck.Items(i).SubItems(4).Text = "失败"

lvCheck.Items(i).SubItems(4).ForeColor = Color.Red

writeErrlog(lvAddrType & ": 失败 " & lvAddrInfo)

End If

lvCheck.Items(i).SubItems(5).Text = Format(Now(), "yyyy-MM-dd HH:mm:ss")

End Sub

实际的icmp协议比较复杂，因此偷懒的使用了My命名空间下的Ping方法：

Private Function getAddrStatePC(ByVal addr As String) As Boolean

Dim siteResponds As Boolean = False

Try

siteResponds = My.Computer.Network.Ping(addr, pingTime) '如果Ping失败返回False

Return siteResponds

Catch ex As Exception

writeErrlog("错误：" & ex.Message)

End Try

End Function

检测网页：

Private Function getAddrStateWww(ByVal addr As String) As Boolean

Dim LinkOk As Boolean = False

Try

Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create(addr), HttpWebRequest)

Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)

If myHttpWebResponse.StatusCode = HttpStatusCode.OK Then

LinkOk = True

Else

LinkOk = False

End If

' Release the resources of the response.

myHttpWebResponse.Close()

Catch e As WebException

writeErrlog("错误：" & e.Message)

Return False

Catch e As Exception

writeErrlog("错误：" & e.Message)

Return False

End Try

Return LinkOk

End Function

如果需要检测的地址不通，或网页不能访问，记录到Log文件：

Private Sub writeErrlog(ByVal errMsg As String)

Dim logfile As String = Application.StartupPath.TrimEnd("\") & "\err.txt"

Dim sw As New StreamWriter(logfile, True)

sw.WriteLine(Format(Now(), "yyyy-MM-dd HH:mm:ss") & " " & errMsg)

sw.Close()

End Sub

由于.net平台下C#和vb.NET很相似，本文也可以为C#爱好者提供参考。

学习更多vb.net知识，请参看vb.net 教程目录

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原文链接：https://blog.csdn.net/uruseibest/article/details/79028490

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