Dim tcpClient As New TcpClient()
     ' Uses the GetStream public method to return the NetworkStream.

        Dim netStream As NetworkStream = tcpClient.GetStream()
        If netStream.CanWrite Then
           Dim sendBytes As [Byte]() = Encoding.UTF8.GetBytes("Is anybody there?")
           netStream.Write(sendBytes, 0, sendBytes.Length)
        Else
           Console.WriteLine("You cannot write data to this stream.")
           tcpClient.Close()
           ' Closing the tcpClient instance does not close the network stream.
           netStream.Close()
           Return
        End If
        If netStream.CanRead Then
           
           ' Reads the NetworkStream into a byte buffer.
           Dim bytes(tcpClient.ReceiveBufferSize) As Byte
           ' Read can return anything from 0 to numBytesToRead. 
           ' This method blocks until at least one byte is read.
           netStream.Read(bytes, 0, CInt(tcpClient.ReceiveBufferSize))
           
           ' Returns the data received from the host to the console.
           Dim returndata As String = Encoding.ASCII.GetString(bytes)
           Console.WriteLine(("This is what the host returned to you: " + returndata))
        Else
           Console.WriteLine("You cannot read data from this stream.")
           tcpClient.Close()
           ' Closing the tcpClient instance does not close the network stream.
           netStream.Close()
           Return
        End If

     ' Uses the Close public method to close the network stream and socket.
     tcpClient.Close()
  End Sub

' 导入命名空间
Imports System.Net.Sockets
Imports System.Net
Imports System.Threading
Imports System.Text

Public Class Tester
    
    Public Shared Sub Main
        Dim myTcpClient As New TcpClient()
        Dim myNetworkStream As NetworkStream

        Try
            myTcpClient.Connect("127.0.0.1", 12345)
            myNetworkStream = myTcpClient.GetStream()
        Catch ex As ArgumentOutOfRangeException
            Console.WriteLine(ex.Message)
        Catch ex As SocketException
            Console.WriteLine(ex.Message)
        End Try

        Dim myBytes() As Byte = Encoding.ASCII.GetBytes("asdf")

        myNetworkStream = myTcpClient.GetStream()
        myNetworkStream.Write(myBytes, 0, myBytes.Length)

        Dim bufferSize As Integer = myTcpClient.ReceiveBufferSize
        Dim myBufferBytes(bufferSize) As Byte

        myNetworkStream.Read(myBufferBytes, 0, bufferSize)
        Console.WriteLine(Encoding.ASCII.GetString(myBufferBytes, 0, bufferSize))
    End Sub
End Class