Okay. First it appeared to work (I am able to connect to the sever) when I was improving my game, but when I tried to connect with another client it didn't connect.

Here's my server code:

Code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If Not serving Then
            Dim slots As Integer = CInt(Replace(TextBox1.Text, " ", Nothing))
            If IsNumeric(slots) Then
                If slots > 0 And slots < 11 Then
                    serving = True
                    Button1.Text = "Serving..."
                    Dim port As Integer = 21760
                    max_players = slots
                    ReDim tcp_listener(max_players)
                    ReDim tcp_client(max_players)
                    For a As Integer = 0 To max_players - 1
                        tcp_listener(a) = New System.Net.Sockets.TcpListener(System.Net.IPAddress.Any, port)
                        tcp_listener(a).Start()
                        port = port + 1
                        Timer1.Start()
                        Timer5.Start()
                    Next
                    Dim thread As New System.Threading.Thread(AddressOf Listen)
                    thread.IsBackground = True
                    thread.Start()
                Else
                    MsgBox("The slots number must be between 1 and 10.", MsgBoxStyle.Critical, "Error")
                End If
            Else
                MsgBox("The slots number must be a number.", MsgBoxStyle.Critical, "Error")
            End If
        End If

   End Sub

   Private Sub Listen(ByVal index As Object)

        Do
            Try
                tcp_client(CInt(index)) = tcp_listener(CInt(index)).AcceptTcpClient
                tcp_listener(CInt(index)).Stop()
                Dim data As String = "connection1|"
                Dim stream_writer As New System.IO.StreamWriter(tcp_client(CInt(index)).GetStream)
                stream_writer.Write(data)
                stream_writer.Flush()
                tcp_client(CInt(index)).GetStream.BeginRead(readBuffer, 0, 255, AddressOf Data_Arrival, Nothing)
                Exit Sub
            Catch ex As Exception
                MsgBox(ex.Message)
            End Try
        Loop

    End Sub
Client code:

Code:
 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If Not connecting Then
            connecting = True
            Button1.Text = "Connecting..."
            TextBox1.ReadOnly = True
            username = TextBox1.Text
            Dim thread As New System.Threading.Thread(AddressOf Connect)
            thread.IsBackground = True
            thread.Start(current_port)
            Timer4.Start()
        End If

    End Sub

    Private Sub Connect(ByVal port As Object)

        Try
            current_port = CInt(port)
            tcp_client = New System.Net.Sockets.TcpClient("ip.ip.ip.ip", CInt(port))
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

If you need any further info just ask.