Fast TCP receive - vb.net

Question

I'm working on a TCP client. but for some reason it is not fast enough receiving data. If the server sends a string (about 140 characters) every 50ms it works fine, but it I change it to 10ms (or lower) the Client doesn't display every string.
I tried the same with another TCP chat program, and there 1ms was no problem.
So it should be possible ;-)
Below my code:
Imports System.Net, System.Text
Imports System.Net.Sockets
Imports System.IO
Imports System.Xml
Imports System.Globalization
Imports System.ComponentModel
Imports System.Management
Imports System.Text.RegularExpressions
Public Class Client
Dim t As New TcpClient
Private Sub Client_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Control.CheckForIllegalCrossThreadCalls = False
Try
t.Connect("127.0.0.1", "50020")
If t.Connected Then
t.GetStream.BeginRead(New Byte() {0}, 0, 0, AddressOf doread, Nothing)
login()
StatusStrip1.BackColor = Color.LightGreen
End If
Catch ex As Exception
Application.Restart()
End Try
End Sub
Sub login()
senddata("LOGIN|")
End Sub
Sub doread(ByVal ar As IAsyncResult)
Try
If t.Connected = True Then
Dim sr As New StreamReader(t.GetStream)
Dim msg As String = sr.ReadLine()
TextBox1.Text = (msg & vbCr & vbLf) & TextBox1.Text
t.GetStream.BeginRead(New Byte() {0}, 0, 0, AddressOf doread, Nothing)
End If
Catch ex As Exception
Application.Restart()
End Try
End Sub
Sub senddata(ByVal message As String)
Dim sw As New StreamWriter(t.GetStream) 'declare a new streamwriter
sw.WriteLine(message) 'write the message
sw.Flush()
End Sub
End Class

Answer 1

You might not be aware of the fact that TCP connections represent a stream of bytes. Messages/packets are not preserved. You might receive as little as one byte at a time.
You assume that you are receiving whole lines.
Also, this hybrid use of binary reads and StreamReader cannot work for many reasons. One of them is that StreamReader buffers internally. Each time you create a new one you throw buffer contents away.
Why are you checking t.Connected all the time? If false, you simply do nothing. This is worse than not checking at all. Don't blindly copy code from the web (I know that you copied this because this broken pattern is all over the web and nobody would normally think of doing this).
Application.Restart
??? That's not an appropriate error strategy. Better: Dispose of all resources and show a message box.
This is really, really broken. Unsalvagable. Need to rewrite.
Simply do this on a background thread:
var sr = new StreamReader(...);
while (true) {
var line = sr.ReadLine();
if (line == null) break;
Invoke(new Action(() => TextBox1.Text += line));
}
Or anything equivalent.