Re: Help with UDP data handler

The callback functionality works fine for me, so I put this answer for the history:

I use Dynamic C 10.70 and RCM6700.

My udp_open:
  int local_port;
  local_port = 2000; // for example
  udp_open(&sock, local_port, -1, 0, comm_udp_rx_packet);

My callback function:
/*** BeginHeader comm_udp_rx_packet */
int comm_udp_rx_packet(int event, void *s, ll_Gather *g, _udp_datagram_info *info);
/*** EndHeader */
int comm_udp_rx_packet(int event, void *s, ll_Gather *g, _udp_datagram_info *info)
{
  comm_udp_header_t *rx_header; // this is custom struct
  char answer[5];
  char cs;
  int i;

  if (
    (event == UDP_DH_INDATA) &&
    (info->len >= sizeof(comm_udp_header_t)) &&
    (memcmp(g->data2, COMM_UDP_PREAMBLE, strlen(COMM_UDP_PREAMBLE)) == 0)
    )
  {
      rx_header = (comm_udp_header_t*)g->data2;
      rx_header->packet_id = ntohs(rx_header->packet_id);
      rx_header->data_length = ntohs(rx_header->data_length);

      // Checksum
      cs = 0;
      for (i=0; i<g->len2-1; i++) cs += g->data2[i];
      if (cs != g->data2[g->len2-1]) {
        answer[0] = ERROR_BAD_CHECKSUM;
        answer[1] = cs;
        answer[2] = g->data2[g->len2-1];
        comm_udp_tx_packet(COMM_UDP_PACKET_ERROR, answer, 3, rx_header);
      }
      else

      // Protocol Version
      if (rx_header->protocol_version != COMM_UDP_PROTOCOL_VERSION) {
        answer[0] = ERROR_BAD_PROTOCOL_VERSION;
        answer[1] = COMM_UDP_PROTOCOL_VERSION;
        answer[2] = rx_header->protocol_version;
        comm_udp_tx_packet(COMM_UDP_PACKET_ERROR, answer, 3, rx_header);
      }
      else {
        remote_ip = info->remip;
        remote_port = info->remport;

        // Good packet, so call the packet handling function.
        comm_udp_rx_packet(rx_header, g->data2); // g->data2 points to the data part in the udp datagram
      }
  }

  // The whole UDP RX traffic is handled in this function,
  // so I don't add any data to the socket buffer for future use
  return 1;
}



---=== Some info from the documentation ===---

Callback function parameters:

Event:
  UDP_DH_INDATA  - Normal received data
  UDP_DH_ICMPMSG - ICMP message received for this socket

ll_Gather: (documented in NET.LIB)
  typedef struct {
    byte iface;   // Destination interface
    byte spare;
    word len1;    // Length of root data section
    void * data1; // UDP header
    word len2;    // Length of first xmem section
    long data2;   // UDP data - xmem physical address
    word len3;    // Length of second xmem section
    long data3;   // not used
  } ll_Gather;

_udp_datagram_info: (documented in udp_peek)
  typedef struct {
    longword remip; // Remote host IP address
    word remport;   // Remote host port number
    int len;        // Length of datagram
    byte flags;     // Bit mask (defined below)
    byte iface;     // Interface number
  } _udp_datagram_info;
  The flags field may have one of the following values:
    UDI_ICMP_ERROR - This is an ICMP error entry.
    UDI_TOS_MASK - Type-of-service bit mask.
    UDI_BROADCAST_LL - Received on broadcast link layer address.
    UDI_BROADCAST_IP - Received on broadcast network (IP) address.

This callback function should return:
  0 - to continue with normal processing (i.e., add the datagram to the socket buffer)
  1 - to indicate that the datagram has been processed and should not be added to the socket buffer