text: /*
   * Copyright (c) 2016 Stephan Linz <linz@li-pro.net>, Li-Pro.Net
   * All rights reserved.
   *
   * Based on examples provided by
   * Iwan Budi Kusnanto <ibk@labhijau.net> (https://gist.github.com/iwanbk/1399729)
   * Juri Haberland <juri@sapienti-sat.org> (https://lists.gnu.org/archive/html/lwip-users/2007-06/msg00078.html)
   *
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice,
   *    this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
   * OF SUCH DAMAGE.
   *
   * This file is part of and a contribution to the lwIP TCP/IP stack.
   *
   * Credits go to Adam Dunkels (and the current maintainers) of this software.
   *
   * Stephan Linz rewrote this file to get a basic echo example.
   */
  
  /**
   * @file
   * UDP echo server example using raw API.
   *
   * Echos all bytes sent by connecting client,
   * and passively closes when client is done.
   *
   */
  
  #include "lwip/opt.h"
  #include "lwip/debug.h"
  #include "lwip/stats.h"
  #include "lwip/udp.h"
  #include "udpecho_raw.h"
  
  #include <stdio.h>
  
  #if LWIP_UDP
  
  static struct udp_pcb *udpecho_raw_pcb;
  
  static void
  udpecho_raw_recv(void *arg, struct udp_pcb *upcb, struct pbuf *p,
                   const ip_addr_t *addr, u16_t port)
  {
    LWIP_UNUSED_ARG(arg);
  
    printf("%s:%u %p\n", __FUNCTION__, __LINE__, p);
  
    if (p != NULL) {
      /* send received packet back to sender */
      udp_sendto(upcb, p, addr, port);
      /* free the pbuf */
      pbuf_free(p);
    }
  }
  
  void
  udpecho_raw_init(void)
  {
    udpecho_raw_pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
    if (udpecho_raw_pcb != NULL) {
      err_t err;
  
      printf("%s:%u\n", __FUNCTION__, __LINE__);
  
      err = udp_bind(udpecho_raw_pcb, IP_ANY_TYPE, 7);
      if (err == ERR_OK) {
        udp_recv(udpecho_raw_pcb, udpecho_raw_recv, NULL);
        printf("%s:%u\n", __FUNCTION__, __LINE__);
      } else {
        /* abort? output diagnostic? */
      }
    } else {
      /* abort? output diagnostic? */
    }
  }
  
  #endif /* LWIP_UDP */
  