Cannot connect TcpClient to TcpListener Visual Basic .NET

Question

I' trying hard to create TCP server and client. I got a lot of tutorials like here and here. But still can't succeed!

Here is my code:

Imports System.Net
Imports System.Net.Sockets
Imports System.Threading
Imports System.Runtime.InteropServices

Public Class Form1

Private Server As TcpListener = Nothing
Private ServerThread As Thread = Nothing
Private WithEvents Tray As New NotifyIcon
Private myClient As TcpClient = Nothing
Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.115")


Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Shown
    Server = New TcpListener(localAddr, 40000)
    ServerThread = New Thread(AddressOf ConnectionListener)
    ServerThread.IsBackground = True
    ServerThread.Start()
    TextBox1.Text = "Server is ready!"

' function I use to get all the TCP clients I can see in local web. 
' You can find it by the first link (see at the top of the post)
    lbComputers.DataSource = GetNetworkComputers() 

End Sub

Private Sub ConnectionListener()
    Try
        Server.Start()
        While True
            myClient = Server.AcceptTcpClient
            'myClient.Connect("MSK4", 40000) 'tried this: didn't work
            Dim T As New Thread(AddressOf SomeClientActions)
            T.Start(myClient)
            TextBox2.Text = "Client connected" ' It's always empty :(

            End While



            myClient.Close()
        End While

    Catch ex As Exception
        MessageBox.Show("Unable to Accept Connections", "Server Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    End Try
    Application.ExitThread()

End Sub

Private Sub SomeClientActions(ByVal client As Object)
    ' ... do something with "client" in here ...
    Invoke(Sub() TextBox2.Text = "This text is never appears :(")
End Sub


Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
    'myClient.Close() 'error is here
    Server.Stop()
End Sub

End Class

And I have two TextBoxes (TextBox1 and TextBox2). I get Server is ready! in the first one but never get anything in the second! So I suppose I can't connect to my server! Code after this row:

myClient = Server.AcceptTcpClient

Is never executes. I tried to use just

myClient.Connect("MSK4", 40000)

As my computer name is MSK4 but then I get my exception and MessageBox. How to realize the connect? What I do wrong?

Answer 1

Making the server listen to 127.0.0.115 means it will only accept connections from that specific IP. To listen for connections from any IP you need to specify 0.0.0.0 or IPAddress.Any.

As for making connections you must use IP-addresses only, computer names won't work.