Try
Dim UDP1client As New UdpClient
UDP1ip = IPAddress.Parse(TextBox1.Text) 'IP yazan textbox
UDP1client.Connect(UDP1ip, TextBox2.Text) 'IP + Port yazan textbox
Dim UDP1byte As Byte() = New Byte() {}
UDP1byte = Encoding.ASCII.GetBytes(TextBox4.Text) 'Textbox4 de 4096 byte string var
UDP1client.Send(UDP1byte, UDP1byte.Length)
Catch ex As SocketException
MsgBox("Sisteme ulaşılamıyor")
End Try
bunu denermisin ?