Como efectuar o ping a um endereço IP, utilizando sockets no Visual Basic .NET

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Requisitos

• Programação com o Visual Basic .NET
• Sockets

• Microsoft Windows 2000, Microsoft Windows XP ou Microsoft Windows Server 2003
• Microsoft Visual Basic .NET

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Declarar uma estrutura de pacotes ICMP

   Structure IcmpPacket
#Region "PUBLIC MEMBER VARIABLES"
      Dim type_message As Byte                ' Type of message.
      Dim subCode_type As Byte                ' Type of sub-code.
      Dim complement_checkSum As UInt16       ' One's complement checksum for the structure.
      Dim identifier As UInt16                ' Identifier.
      Dim sequenceNumber As UInt16            ' Sequence number.
      Dim data() As Byte                      ' Data.
#End Region


#Region "PUBLIC MEMBER METHODS"
      Public Sub Initialize(ByVal type As Byte, ByVal subCode As Byte, ByVal payload() As Byte)
         Dim index As Integer
         Dim buffer_icmpPacket() As Byte
         Dim cksumBuffer() As UInt16
         Dim icmpHeaderBufferIndex As Int32 = 0
         Me.type_message = type
         Me.subCode_type = subCode
         complement_checkSum = UInt16.Parse("0")
         identifier = UInt16.Parse("45")
         sequenceNumber = UInt16.Parse("0")
         Data = payload

         ' Declare a variable to store the total packet size.
         ' Call the Serialize method to count the total number of bytes in the packet.
         buffer_icmpPacket = Serialize()

         ' Resize a UInt16 array to half the size of the packet.
         ReDim cksumBuffer((buffer_icmpPacket.Length() \ 2) - 1)

         ' Initialize the UInt16 array.
         For index = 0 To (cksumBuffer.Length() - 1)
            cksumBuffer(index) = BitConverter.ToUInt16(buffer_icmpPacket, icmpHeaderBufferIndex)
            icmpHeaderBufferIndex += 2
         Next index

         'Call a method that returns a checksum.
         complement_checkSum = MCheckSum.Calculate(cksumBuffer, cksumBuffer.Length())
      End Sub

      Public Function Size() As Integer
         Return (8 + Data.Length())
      End Function

      ' The Serialize method converts the packet to a byte array to calculate the total size.
      Public Function Serialize() As Byte()
         Dim b_seq() As Byte = BitConverter.GetBytes(sequenceNumber)
         Dim b_cksum() As Byte = BitConverter.GetBytes(complement_checkSum)
         Dim b_id() As Byte = BitConverter.GetBytes(identifier)
         Dim index As Int32 = 0
         Dim buffer() As Byte
         ReDim buffer(Size() - 1)

         ' Serialize the structure into the array.
         buffer(0) = type_message
         buffer(1) = subCode_type
         index += 2
         Array.Copy(b_cksum, 0, buffer, index, 2)
         index += 2
         Array.Copy(b_id, 0, buffer, index, 2)
         index += 2
         Array.Copy(b_seq, 0, buffer, index, 2)
         index += 2

         ' Copy the data.
         If (Data.Length() > 0) Then
            Array.Copy(Data, 0, buffer, index, Data.Length())
         End If
         Return buffer
      End Function
#End Region
   End Structure

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Definir a classe CPing

   ' The CPing class.
   Public Class CPing
#Region "MEMBER CONSTANTS"
      Private Const DEFAULT_TIMEOUT As Integer = 1000
      Private Const SOCKET_ERROR As Integer = -1
      Private Const PING_ERROR As Integer = -1
      Private Const ICMP_ECHO As Integer = 8
      Private Const DATA_SIZE As Integer = 32
      Private Const RECV_SIZE As Integer = 128
#End Region

#Region "MEMBER VARIABLES"
      Private _open As Boolean = False
      Private _initialized As Boolean
      Private _recvBuffer() As Byte
      Private _packet As IcmpPacket
      Private _hostName As String
      Private _server As EndPoint
      Private _local As EndPoint
      Private _socket As Socket

#End Region

#Region "CONSTRUCTORS & FINALIZER"
      Public Sub New(ByVal hostName As String)
         Me.HostName() = hostName
         ReDim _recvBuffer(RECV_SIZE - 1)
      End Sub

      Public Sub New()
         ' Set the default host name to the local host.
         Me.HostName() = Dns.GetHostName()
         ReDim _recvBuffer(RECV_SIZE - 1)
      End Sub

      Private Overloads Sub finalize()
         ' Make sure that you close the socket.
         Me.Close()
         Erase _recvBuffer
      End Sub
#End Region

#Region "MEMBER METHODS"
      ' Get and set the current host name.
      Public Property HostName() As String
         Get
            Return _hostName
         End Get
         Set(ByVal Value As String)
            _hostName = Value
            ' If the CPing object is already open, close it and then reopen it by using a new host name.
            If (_open) Then
               Me.Close()
               Me.Open()
            End If
         End Set
      End Property

      ' Get the state (open or closed).
      Public ReadOnly Property IsOpen() As Boolean
         Get
            Return _open
         End Get
      End Property

      ' Create a socket to host remote end points and local end points.
      Public Function Open() As Boolean
         Dim payload() As Byte

         If (Not _open) Then
            Try
               ' Initialize the packet.
               ReDim payload(DATA_SIZE)
               _packet.Initialize(ICMP_ECHO, 0, payload)

               ' Initialize an ICMP socket.
               _socket = New Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp)

               ' Set the server end point.
               _server = New IPEndPoint(Dns.GetHostByName(_hostName).AddressList(0), 0)

               ' Set the receiving end point as your client computer.
               _local = New IPEndPoint(Dns.GetHostByName(Dns.GetHostName()).AddressList(0), 0)
               _open = True
            Catch
               Return False
            End Try
         End If
         Return True
      End Function

      ' Destroy the socket and the end points (if necessary).
      Public Function Close() As Boolean
         If (_open) Then
            _socket.Close()
            _socket = Nothing
            _server = Nothing
            _local = Nothing
            _open = False
         End If
         Return True
      End Function

      ' Perform a PING operation.
      Public Overloads Function Ping() As Integer
         Return Ping(DEFAULT_TIMEOUT)
      End Function

      ' The Ping method performs a PING operation.
      Public Overloads Function Ping(ByVal timeOutMilliSeconds As Integer) As Integer

         ' Initialize the time-out value.
         Dim timeOut As Integer = timeOutMilliSeconds + Environment.TickCount()

         ' Send the packet.
         If (SOCKET_ERROR = _socket.SendTo(_packet.Serialize(), _packet.Size(), 0, _server)) Then
            Return PING_ERROR
         End If

         ' Use the following loop to check the response time until you receive a time-out.
         Do
            ' Poll the read buffer every millisecond.
            ' If data exists, read the data and return the round-trip time.
            If (_socket.Poll(1000, SelectMode.SelectRead)) Then
               _socket.ReceiveFrom(_recvBuffer, RECV_SIZE, 0, _local)
               Return (timeOutMilliSeconds - (timeOut - Environment.TickCount()))
            ElseIf (Environment.TickCount() >= timeOut) Then
               Return PING_ERROR
            End If
         Loop While (True)
      End Function
#End Region
   End Class

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Calcular o valor de soma de verificação

#Region "MEMBER METHODS"
      <StructLayout(LayoutKind.Explicit)> _
                 Structure UNION_INT16
         <FieldOffset(0)> Dim lsb As Byte      ' Least significant byte
         <FieldOffset(1)> Dim msb As Byte      ' Most significant byte
         <FieldOffset(0)> Dim w16 As Short
      End Structure

      <StructLayout(LayoutKind.Explicit)> _
      Structure UNION_INT32
         <FieldOffset(0)> Dim lsw As UNION_INT16     ' Most significant word
         <FieldOffset(2)> Dim msw As UNION_INT16     ' Least significant word
         <FieldOffset(0)> Dim w32 As Integer
      End Structure

      ' The Calculate method calculates the checksum value.
      Public Function Calculate(ByRef buffer() As UInt16, ByVal size As Int32) As UInt16
         Dim counter As Int32 = 0
         Dim cksum32 As UNION_INT32
         Do While (size > 0)
            cksum32.w32 += Convert.ToInt32(buffer(counter))
            counter += 1
            size -= 1
         Loop

         cksum32.w32 = cksum32.msw.w16 + cksum32.lsw.w16 + cksum32.msw.w16
         Return Convert.ToUInt16(cksum32.lsw.w16 Xor &HFFFF)
      End Function
#End Region

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Implementa a interface de utilizador

Sub Main()
   Dim Packet As New ICMP_Packet.CPing()
   Dim retValue

   Console.WriteLine("Enter the IP address or the host name to ping: ")

   ' Accept a host name or an IP address.
   Packet.HostName = Trim(Console.ReadLine())

   ' Determine whether the user has typed only spaces instead of a host name or an IP address.
   If Packet.HostName = "" Then
      Console.WriteLine("Please enter an IP address (in the N.N.N.N format) or a host name")
   Else
      ' Determine whether you can establish a socket connection to the IP address.
      If Packet.Open Then
         ' Establish a socket connection, and then send a packet using ICMP.
         retValue = Packet.Ping
         If retValue <> -1 Then
            ' Display the response time in milliseconds.
            Console.WriteLine("Approximate response time : " & retValue)
         Else
            Console.WriteLine("Host Unreachable")
         End If
      Else
         Console.WriteLine("No host found")
      End If
      
      Packet.Close()

   End If

   Console.WriteLine("Press ENTER to quit.")
   Console.ReadLine()

End Sub

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Criar uma aplicação de consola

1. Inicie o Microsoft Visual Studio NET..
2. No menu ficheiro , aponte para Novo e, em seguida, clique em projecto . A caixa de diálogo novo projecto é apresentada.
3. Em Project Types , clique em Projectos do Visual Basic .
4. Em modelos , clique em consola aplicação .
5. Na caixa nome , escreva MyConsoleApplication .
   
   Nota MyConsoleApplication é um exemplo do Visual Basic .NET aplicação.
6. Na caixa localização , escreva a localização onde pretende guardar o projecto MyConsoleApplication e, em seguida, clique em OK .
   
   Por predefinição, o ficheiro Module1.vb é criado.
7. No ficheiro Module1.vb, substitua o código existente com o seguinte código:

   Imports System.Net.Sockets
   Imports System.Net
   Imports System
   Imports System.Runtime.InteropServices
   
   Namespace ICMP_Packet
   
      ' Define the structure of an ICMP packet.
      ' This structure contains packet information.
      Structure IcmpPacket
   #Region "PUBLIC MEMBER VARIABLES"
         Dim type_message As Byte                ' type of message
         Dim subCode_type As Byte                ' type of sub-code
         Dim complement_checkSum As UInt16       ' one's complement checksum for the structure
         Dim identifier As UInt16                ' identifier
         Dim sequenceNumber As UInt16            ' sequence number  
         Dim data() As Byte                      ' data
   #End Region
   
   
   #Region "PUBLIC MEMBER METHODS"
         Public Sub Initialize(ByVal type As Byte, ByVal subCode As Byte, ByVal payload() As Byte)
            Dim index As Integer
            Dim buffer_icmpPacket() As Byte
            Dim cksumBuffer() As UInt16
            Dim icmpHeaderBufferIndex As Int32 = 0
            Me.type_message = type
            Me.subCode_type = subCode
            complement_checkSum = UInt16.Parse("0")
            identifier = UInt16.Parse("45")
            sequenceNumber = UInt16.Parse("0")
            Data = payload
   
            ' Declare a variable to store the total packet size.
            ' Call the Serialize method to count the total number of bytes in the packet.
            buffer_icmpPacket = Serialize()
   
            ' Resize a UInt16 array to half the size of the packet.
            ReDim cksumBuffer((buffer_icmpPacket.Length() \ 2) - 1)
   
            ' Initialize the UInt16 array.
            For index = 0 To (cksumBuffer.Length() - 1)
               cksumBuffer(index) = BitConverter.ToUInt16(buffer_icmpPacket, icmpHeaderBufferIndex)
               icmpHeaderBufferIndex += 2
            Next index
   
            'Call a method that returns a checksum.
            complement_checkSum = MCheckSum.Calculate(cksumBuffer, cksumBuffer.Length())
         End Sub
   
         Public Function Size() As Integer
            Return (8 + Data.Length())
         End Function
   
         ' The Serialize method converts the packet to a byte array to calculate the total size.
         Public Function Serialize() As Byte()
            Dim b_seq() As Byte = BitConverter.GetBytes(sequenceNumber)
            Dim b_cksum() As Byte = BitConverter.GetBytes(complement_checkSum)
            Dim b_id() As Byte = BitConverter.GetBytes(identifier)
            Dim index As Int32 = 0
            Dim buffer() As Byte
            ReDim buffer(Size() - 1)
   
            ' Serialize the structure into the array.
            buffer(0) = type_message
            buffer(1) = subCode_type
            index += 2
            Array.Copy(b_cksum, 0, buffer, index, 2)
            index += 2
            Array.Copy(b_id, 0, buffer, index, 2)
            index += 2
            Array.Copy(b_seq, 0, buffer, index, 2)
            index += 2
   
            ' Copy the data.
            If (Data.Length() > 0) Then
               Array.Copy(Data, 0, buffer, index, Data.Length())
            End If
            Return buffer
         End Function
   #End Region
      End Structure
   
      ' The CPing class.
      Public Class CPing
   #Region "MEMBER CONSTANTS"
         Private Const DEFAULT_TIMEOUT As Integer = 1000
         Private Const SOCKET_ERROR As Integer = -1
         Private Const PING_ERROR As Integer = -1
         Private Const ICMP_ECHO As Integer = 8
         Private Const DATA_SIZE As Integer = 32
         Private Const RECV_SIZE As Integer = 128
   #End Region
   
   #Region "MEMBER VARIABLES"
         Private _open As Boolean = False
         Private _initialized As Boolean
         Private _recvBuffer() As Byte
         Private _packet As IcmpPacket
         Private _hostName As String
         Private _server As EndPoint
         Private _local As EndPoint
         Private _socket As Socket
   
   #End Region
   
   #Region "CONSTRUCTORS & FINALIZER"
         Public Sub New(ByVal hostName As String)
            Me.HostName() = hostName
            ReDim _recvBuffer(RECV_SIZE - 1)
         End Sub
   
         Public Sub New()
            ' Set the default host name to the local host.
            Me.HostName() = Dns.GetHostName()
            ReDim _recvBuffer(RECV_SIZE - 1)
         End Sub
   
         Private Overloads Sub finalize()
            ' Ensure that you close the socket.
            Me.Close()
            Erase _recvBuffer
         End Sub
   #End Region
   
   #Region "MEMBER METHODS"
         ' Get and set the current host name.
         Public Property HostName() As String
            Get
               Return _hostName
            End Get
            Set(ByVal Value As String)
               _hostName = Value
               ' If the CPing object is already open, close it and then reopen it by using a new host name.
               If (_open) Then
                  Me.Close()
                  Me.Open()
               End If
            End Set
         End Property
   
         ' Get the state (open or closed).
         Public ReadOnly Property IsOpen() As Boolean
            Get
               Return _open
            End Get
         End Property
   
         ' Create a socket to host remote end points and local end points.
         Public Function Open() As Boolean
            Dim payload() As Byte
   
            If (Not _open) Then
               Try
                  ' Initialize the packet.
                  ReDim payload(DATA_SIZE)
                  _packet.Initialize(ICMP_ECHO, 0, payload)
   
                  ' Initialize an ICMP socket.
                  _socket = New Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp)
   
                  ' Set the server end point.
                  _server = New IPEndPoint(Dns.GetHostByName(_hostName).AddressList(0), 0)
   
                  ' Set the receiving end point as your client computer.
                  _local = New IPEndPoint(Dns.GetHostByName(Dns.GetHostName()).AddressList(0), 0)
                  _open = True
               Catch
                  Return False
               End Try
            End If
            Return True
         End Function
   
         ' Destroy the socket and end points (if necessary).
         Public Function Close() As Boolean
            If (_open) Then
               _socket.Close()
               _socket = Nothing
               _server = Nothing
               _local = Nothing
               _open = False
            End If
            Return True
         End Function
   
         ' Perform a PING operation.
         Public Overloads Function Ping() As Integer
            Return Ping(DEFAULT_TIMEOUT)
         End Function
   
         ' The Ping method performs a PING operation.
         Public Overloads Function Ping(ByVal timeOutMilliSeconds As Integer) As Integer
   
            ' Initialize the time-out value.
            Dim timeOut As Integer = timeOutMilliSeconds + Environment.TickCount()
   
            ' Send the packet.
            If (SOCKET_ERROR = _socket.SendTo(_packet.Serialize(), _packet.Size(), 0, _server)) Then
               Return PING_ERROR
            End If
   
            ' Use the following loop to check the response time until you receive a time-out.
            Do
               ' Poll the read buffer every millisecond.
               ' If data exists, read the data and return the round-trip time.
               If (_socket.Poll(1000, SelectMode.SelectRead)) Then
                  _socket.ReceiveFrom(_recvBuffer, RECV_SIZE, 0, _local)
                  Return (timeOutMilliSeconds - (timeOut - Environment.TickCount()))
               ElseIf (Environment.TickCount() >= timeOut) Then
                  Return PING_ERROR
               End If
            Loop While (True)
         End Function
   #End Region
      End Class
   
      ' The MCheckSum module contains the static Calculate method.
      Module MCheckSum
   #Region "MEMBER METHODS"
         <StructLayout(LayoutKind.Explicit)> _
                    Structure UNION_INT16
            <FieldOffset(0)> Dim lsb As Byte      ' Least significant byte
            <FieldOffset(1)> Dim msb As Byte      ' Most significant byte
            <FieldOffset(0)> Dim w16 As Short
         End Structure
   
         <StructLayout(LayoutKind.Explicit)> _
         Structure UNION_INT32
            <FieldOffset(0)> Dim lsw As UNION_INT16     ' Most significant word
            <FieldOffset(2)> Dim msw As UNION_INT16     ' Least significant word
            <FieldOffset(0)> Dim w32 As Integer
         End Structure
   
         ' The Calculate method calculates the checksum value.
         Public Function Calculate(ByRef buffer() As UInt16, ByVal size As Int32) As UInt16
            Dim counter As Int32 = 0
            Dim cksum32 As UNION_INT32
            Do While (size > 0)
               cksum32.w32 += Convert.ToInt32(buffer(counter))
               counter += 1
               size -= 1
            Loop
   
            cksum32.w32 = cksum32.msw.w16 + cksum32.lsw.w16 + cksum32.msw.w16
            Return Convert.ToUInt16(cksum32.lsw.w16 Xor &HFFFF)
         End Function
   #End Region
   
         Sub Main()
            Dim Packet As New ICMP_Packet.CPing()
            Dim retValue
   
            Console.WriteLine("Enter the IP address or the host name to ping: ")
   
            ' Accept a host name or an IP address.
            Packet.HostName = Trim(Console.ReadLine())
   
            ' Determine whether the user has typed only spaces instead of a host name or an IP address.
            If Packet.HostName = "" Then
               Console.WriteLine("Please enter an IP address (in the N.N.N.N format) or a host name")
            Else
               ' Determine whether you can establish a socket connection to the IP address.
               If Packet.Open Then
                  ' Establish a socket connection, and then send a packet by using ICMP.
                  retValue = Packet.Ping
                  If retValue <> -1 Then
                     ' Display the response time in milliseconds.
                     Console.WriteLine("Approximate response time : " & retValue)
                  Else
                     Console.WriteLine("Host Unreachable")
                  End If
               Else
                  Console.WriteLine("No host found")
               End If
               
               Packet.Close()
   
            End If
   
            Console.WriteLine("Press ENTER to quit.")
            Console.ReadLine()
   
         End Sub
      End Module
   
   End Namespace

8. No Solution Explorer, clique no projecto MyConsoleApplication .
9. No menu projecto , clique em Propriedades .
10. Nas Páginas de propriedades MyConsoleApplication caixa de diálogo, seleccione Sub Main do arranque objecto lista pendente e, em seguida, clique em OK .
11. No menu Debug , clique em Iniciar .
12. Na linha de comandos que aparece, escreva um nome de anfitrião ou um endereço IP e, em seguida, prima ENTER.

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