Well, it depends on what you want to get back. Here's a quick example that access www.microsoft.com:
Code:
  Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim client As New TcpClient()
    client.Connect("www.microsoft.com", 80)
    Dim textToSend As String = "GET / HTTP/1.1" & vbCrLf & _
                               "Host: microsoft.com" & vbCrLf & _
                               vbCrLf

    Dim data As Byte() = System.Text.Encoding.ASCII.GetBytes(textToSend)
    Using stream As NetworkStream = client.GetStream()
      stream.Write(data, 0, data.Length)
      data = New Byte(1024) {}

      Dim bytes As Integer = 0
      Dim responseText As String = ""
      Do
        bytes = stream.Read(data, 0, data.Length)
        responseText &= System.Text.Encoding.ASCII.GetString(data, 0, bytes)
      Loop While stream.DataAvailable

      MessageBox.Show(responseText)
    End Using
    client.Close()
  End Sub
However if you want to access web servers you should really look into the WebClient class instead of using TcpClient.