VB.netにてTCP/IP接続
VB.net 2002用サーバー	2003の場合は下のほうにあります。
ーーーーサーバーーーーー 
   Sub Main()
        Const portNum As Integer = 1000 '待機するポート番号を指定
        Dim listener As New System.Net.Sockets.TcpListener(portNum)
        listener.Start()

        While True
            Console.Write("Waiting for connection...")
            Dim client As System.Net.Sockets.TcpClient = listener.AcceptTcpClient()
            Console.WriteLine("Connection accepted.")
            Dim ns As System.Net.Sockets.NetworkStream = client.GetStream()

            '----送信部分----
            Dim word As Byte() = System.Text.Encoding.Default.GetBytes("今日は")
            ns.Write(word, 0, word.Length)

            '----受信部分----
            Dim getWord(1024) As Byte
            Dim bytesRead As Integer = ns.Read(getWord, 0, getWord.Length)
            Console.WriteLine(System.Text.Encoding.Default.GetString(getWord, 0, bytesRead))

            ns.Close()
            client.Close()
        End While

        listener.Stop()

    End Sub

ーーーークライアントーーーー
VB.net 2002 2003ともに動きます

    Sub Main()
        Dim portNum As Integer = 1000 'ポート番号を指定
        Dim hostName As String = "localhost" 'アドレスを指定
        Dim client As New System.Net.Sockets.TcpClient(hostName, portNum)
        Dim ns As System.Net.Sockets.NetworkStream = client.GetStream()

        '----受信----
        Dim bytes(1024) As Byte
        Dim bytesRead As Integer = ns.Read(bytes, 0, bytes.Length)
        Debug.WriteLine(System.Text.Encoding.Default.GetString(bytes, 0, bytesRead))

        '----送信----
        Dim word As Byte() = System.Text.Encoding.Default.GetBytes("晴天")
        ns.Write(word, 0, word.Length)

        ns.Close()
        client.Close()
    End Sub

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VB.net 2003では上のコードでは動きませんでした
以下が２００３対応のコードです


ーーーーサーバーーーーー 
    Private Sub Thread1()
        Dim portNum As Integer = 1000 '待機するポート番号を指定

        Dim ipAddress As System.Net.IPAddress = System.Net.Dns.Resolve(System.Net.Dns.GetHostName()).AddressList(0)
        Dim ipLocalEndPoint As New System.Net.IPEndPoint(ipAddress, portNum)

        Dim listener As New System.Net.Sockets.TcpListener(ipLocalEndPoint)

        listener.Start()

        While True
            Console.Write("Waiting for connection...")
            Dim client As System.Net.Sockets.TcpClient = listener.AcceptTcpClient()
            Console.WriteLine("Connection accepted.")
            Dim ns As System.Net.Sockets.NetworkStream = client.GetStream()
            Try
                '----送信部分----
                Dim word As Byte() = System.Text.Encoding.Default.GetBytes("今日は")
                ns.Write(word, 0, word.Length)

                '----受信部分----
                Dim getWord(1024) As Byte
                Dim bytesRead As Integer = ns.Read(getWord, 0, getWord.Length)
                TextBox1.Text = System.Text.Encoding.Default.GetString(getWord, 0, bytesRead)
            Catch ex As Exception
                Console.WriteLine("err : " + ex.ToString)
            End Try
            ns.Close()
            client.Close()
        End While

        listener.Stop()
    End Sub