Question

我在Visual Basic中使用简单的TCP / IP聊天应用程序时遇到问题。当我运行服务器应用程序时，它的窗口没有显示，我不知道为什么。但是，服务器正常工作。服务器代码如下所示。

Imports System.Net.Sockets
Imports System.Net

Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Try

        Dim server As TcpListener
        server = Nothing

        ' Set the TcpListener on port 13000. 
        Dim port As Int32 = 13000
        Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.1")

        server = New TcpListener(localAddr, port)

        ' Start listening for client requests.
        server.Start()

        ' Buffer for reading data 
        Dim bytes(1024) As Byte
        Dim data As String = Nothing

        ' Enter the listening loop. 
        While True
            TextBox1.Text = "Waiting For connections"

            ' Perform a blocking call to accept requests. 
            ' You could also user server.AcceptSocket() here. 
            Dim client As TcpClient = server.AcceptTcpClient()

            TextBox2.Text = "Connected!"

            data = Nothing

            ' Get a stream object for reading and writing 
            Dim stream As NetworkStream = client.GetStream()

            Dim i As Int32

            ' Loop to receive all the data sent by the client.
            i = stream.Read(bytes, 0, bytes.Length)

            While (i > 0)
                ' Translate data bytes to a ASCII string.
                data = System.Text.Encoding.ASCII.GetString(bytes, 0, i)
                TextBox3.Text = "Received:" & data

                ' Process the data sent by the client.
                data = data.ToUpper()
                Dim msg As Byte() = System.Text.Encoding.ASCII.GetBytes(data)

                ' Send back a response.
                stream.Write(msg, 0, msg.Length)
                TextBox4.Text = "Sent:" & data

                i = stream.Read(bytes, 0, bytes.Length)

            End While

            ' Shutdown and end connection
            client.Close()
        End While

        server.Stop()
    Catch ex As Exception

    End Try
End Sub
End Class

Answer 1

您正在Form.Load的UI线程上运行服务器。在Form.Load完成之前，您的表单将不可见。您应该在新线程上运行服务器逻辑。您将遇到的问题是您无法从非UI线程更新UI（例如TextBox1.Text = "Waiting For connections"），因此您需要使用Invoke。例如（完全没有经过测试，只是为了让你知道该尝试什么）：

Imports System.Threading

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim t = New Thread(AddressOf RunServer)
    t.Start()
End Sub

Private Sub RunServer()
    ' Move your code from Form1_Load here, but when updating the UI,
    ' use something like:
    Me.Invoke(Sub() TextBox1.Text = "Waiting For connections")
End Sub

运行应用程序时不显示窗口

1 个答案: