'********* 代码开始 **********'
Imports System.Net.Sockets
'使用到TcpListen类
Imports System.Threading
'使用到线程
Imports System.IO
'使用到StreamReader类
Imports System.Net

Public Class Form1

    Private iPort As Integer = 8000
    '定义侦听端口号
    Private thThreadRead As Thread
    '创建线程，用以侦听端口号，接收信息
    Private tlTcpListen As TcpListener
    '侦听端口号
    Private blistener As Boolean = True
    '设定标示位，判断侦听状态
    Private nsStream As NetworkStream
    '创建接收的基本数据流
    Private srRead As StreamReader
    '从网络基础数据流中读取数据
    Private tcClient As TcpClient

    Private Sub Listen()
        Try
            Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.1")
            tlTcpListen = New TcpListener(localAddr, iPort)
            '以8000端口号来初始化TcpListener实例
            tlTcpListen.Start()
            '开始监听
            StatusBar1.Text = "正在监听..."
            tcClient = tlTcpListen.AcceptTcpClient()
            '通过TCP连接请求
            nsStream = tcClient.GetStream()
            '获取用以发送、接收数据的网络基础数据流
            srRead = New StreamReader(nsStream)
            '以得到的网络基础数据流来初始化StreamReader实例
            StatusBar1.Text = "已经建立TCP连接！"
            '循环侦听
            While blistener
                Dim sMessage As String = srRead.ReadLine()
                '从网络基础数据流中读取一行数据
                If (sMessage = "STOP") Then
                    tlTcpListen.Stop()
                    '关闭侦听
                    nsStream.Close()
                    srRead.Close()
                    '释放资源
                    StatusBar1.Text = "无连接！"
                    thThreadRead.Abort()
                    '中止线程
                    Return
                Else
                    '判断是否为断开TCP连接控制码
                    Dim sTime As String = DateTime.Now.ToLongTimeString()
                    '获取接收数据时的时间
                    SetText(sTime + " " + sMessage)
                End If
            End While
        Catch ex As System.Security.SecurityException
            MessageBox.Show("侦听失败！", "错误")
        End Try
    End Sub

    Private Sub SetText(ByVal [text] As String)
        ' InvokeRequired required compares the thread ID of the' calling thread to the
        ' thread ID of the creating thread.' If these threads are different, it returns true.
        If Me.ListBox1.InvokeRequired Then
            Dim d As New ContextCallback(AddressOf SetText)
            Me.Invoke(d, New Object() {[text]})
        Else
            Me.ListBox1.Items.Add([text])
        End If
    End Sub

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        thThreadRead = New Thread(New ThreadStart(AddressOf Listen))
        '以Listen过程来初始化线程实例
        thThreadRead.Start()
        '启动线程
        Button1.Enabled = False
        Label1.Text = "服务已经启动！"
        Label1.ForeColor = Color.Red
    End Sub

    Private Sub Form1_Disposed(sender As Object, e As System.EventArgs) Handles Me.Disposed
        Try
            thThreadRead.Abort() '中止线程
            tlTcpListen.Stop() '关闭侦听
            tcClient.Close()
            nsStream.Close()
            srRead.Close() '释放资源
        Catch
        End Try
        If Disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(Disposing)
    End Sub

End Class
'********* 代码结束 **********'

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