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Open topic with navigation CAPL Functions » TCP/IP API » OnIpSendPrepare

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OnIpSendPrepare

Valid for: CANoe DE • CANoe4SW DE

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Function Syntax

long OnIpSendPrepare( dword socket, ethernetPacket * packet);

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Description

If the CAPL program implements this callback it is called right before a packet will be sent by the TCP/IP stack. It is possible to manipulate the content of the packet or to block the sending of the package on the bus. Note: The callback is only available for simulation nodes using the individual TCP/IP stack instance. Check this setting in the TCP/IP Stack configuration dialog.

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Parameters

  • socket: The socket handle.
  • packet: The Ethernet packet which will be sent.

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Return Values

  • 0: Block the Ethernet packet.
  • 1: Send the Ethernet packet.

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Example

variables
{
  const dword INVALID_SOCKET = ~0;
  DWORD gUdpSocket;
}

on start
{
  dword result;
  char data[100] = "Hello world";
  // open udp socket
  gUdpSocket = UdpOpen(0, 0);
  if(gUdpSocket == INVALID_SOCKET)
  {
    writeLineEx(1,3,"%BASE_FILE_NAME%: Failed to open udp socket. Error: %d", IpGetLastError());
  }
  // send data on udp socket
  result = UdpSendTo(gUdpSocket, ipGetAddressAsNumber("192.168.1.1"), 21, data, strlen(data));
  if(result != 0)
  {
    writeLineEx(1,3,"%BASE_FILE_NAME%: Failed to send data on udp socket. Error: %d", IpGetLastSocketError(gUdpSocket));
  }
}

long OnIpSendPrepare( dword socket, ethernetPacket * packet)
{
  if(socket == gUdpSocket)
  {
    // change destination MAC id to broadcast
    packet.destination = ethGetMacAddressAsNumber("FF:FF:FF:FF:FF:FF");
    // change ip destination address to broadcast address.
    // Since this address is covered by the IP checksum this will
    // lead to a checksum error.
    packet.dword(16) = ipGetAddressAsNumber("255.255.255.255");
  }
  return 1; // send packet
}