text: /**
   * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
   * All rights reserved. 
   * 
   * 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.
   *
   * Christiaan Simons rewrote this file to get a more stable echo application.
   *
   **/
  
   /* This file was modified by ST */
  
  #include "tcp_echoserver.h"
  #include "lwip/debug.h"
  #include "lwip/stats.h"
  #include "lwip/tcp.h"
  #include "main.h"
  #if LWIP_TCP
  
  static struct tcp_pcb *tcp_echoserver_pcb;
  
  /* ECHO protocol states */
  enum tcp_echoserver_states
  {
    ES_NONE = 0,
    ES_ACCEPTED,
    ES_RECEIVED,
    ES_CLOSING
  };
  
  /* structure for maintaing connection infos to be passed as argument 
     to LwIP callbacks*/
  struct tcp_echoserver_struct
  {
    u8_t state;             /* current connection state */
    u8_t retries;
    struct tcp_pcb *pcb;    /* pointer on the current tcp_pcb */
    struct pbuf *p;         /* pointer on the received/to be transmitted pbuf */
  };
  
  
  static err_t tcp_echoserver_accept(void *arg, struct tcp_pcb *newpcb, err_t err);
  static err_t tcp_echoserver_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err);
  static void tcp_echoserver_error(void *arg, err_t err);
  static err_t tcp_echoserver_poll(void *arg, struct tcp_pcb *tpcb);
  static err_t tcp_echoserver_sent(void *arg, struct tcp_pcb *tpcb, u16_t len);
  static void tcp_echoserver_send(struct tcp_pcb *tpcb, struct tcp_echoserver_struct *es);
  static void tcp_echoserver_connection_close(struct tcp_pcb *tpcb, struct tcp_echoserver_struct *es);
  
  
  /**
    * @brief  Initializes the tcp echo server
    * @param  None
    * @retval None
    */
  void tcp_echoserver_init(void)
  {
    /* create new tcp pcb */
    tcp_echoserver_pcb = tcp_new();
  
    if (tcp_echoserver_pcb != NULL)
    {
      err_t err;
      
      /* bind echo_pcb to port 7 (ECHO protocol) */
      err = tcp_bind(tcp_echoserver_pcb, IP_ADDR_ANY, SERVER_PORT);
      
      if (err == ERR_OK)
      {
        /* start tcp listening for echo_pcb */
        tcp_echoserver_pcb = tcp_listen(tcp_echoserver_pcb);
        
        /* initialize LwIP tcp_accept callback function */
        tcp_accept(tcp_echoserver_pcb, tcp_echoserver_accept);
      }
      else 
      {
        /* deallocate the pcb */
        memp_free(MEMP_TCP_PCB, tcp_echoserver_pcb);
      }
    }
  }
  
  /**
    * @brief  This function is the implementation of tcp_accept LwIP callback
    * @param  arg: not used
    * @param  newpcb: pointer on tcp_pcb struct for the newly created tcp connection
    * @param  err: not used 
    * @retval err_t: error status
    */
  static err_t tcp_echoserver_accept(void *arg, struct tcp_pcb *newpcb, err_t err)
  {
    err_t ret_err;
    struct tcp_echoserver_struct *es;
  
    LWIP_UNUSED_ARG(arg);
    LWIP_UNUSED_ARG(err);
  
    /* set priority for the newly accepted tcp connection newpcb */
    tcp_setprio(newpcb, TCP_PRIO_MIN);
  
    /* allocate structure es to maintain tcp connection informations */
    es = (struct tcp_echoserver_struct *)mem_malloc(sizeof(struct tcp_echoserver_struct));
    if (es != NULL)
    {
      es->state = ES_ACCEPTED;
      es->pcb = newpcb;
      es->retries = 0;
      es->p = NULL;
      
      /* pass newly allocated es structure as argument to newpcb */
      tcp_arg(newpcb, es);
      
      /* initialize lwip tcp_recv callback function for newpcb  */ 
      tcp_recv(newpcb, tcp_echoserver_recv);
      
      /* initialize lwip tcp_err callback function for newpcb  */
      tcp_err(newpcb, tcp_echoserver_error);
      
      /* initialize lwip tcp_poll callback function for newpcb */
      tcp_poll(newpcb, tcp_echoserver_poll, 0);
      
      ret_err = ERR_OK;
    }
    else
    {
      /*  close tcp connection */
      tcp_echoserver_connection_close(newpcb, es);
      /* return memory error */
      ret_err = ERR_MEM;
    }
    return ret_err;  
  }
  
  
  /**
    * @brief  This function is the implementation for tcp_recv LwIP callback
    * @param  arg: pointer on a argument for the tcp_pcb connection
    * @param  tpcb: pointer on the tcp_pcb connection
    * @param  pbuf: pointer on the received pbuf
    * @param  err: error information regarding the reveived pbuf
    * @retval err_t: error code
    */
  static err_t tcp_echoserver_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)
  {
    struct tcp_echoserver_struct *es;
    err_t ret_err;
  
    LWIP_ASSERT("arg != NULL",arg != NULL);
    
    es = (struct tcp_echoserver_struct *)arg;
    
    /* if we receive an empty tcp frame from client => close connection */
    if (p == NULL)
    {
      /* remote host closed connection */
      es->state = ES_CLOSING;
      if(es->p == NULL)
      {
         /* we're done sending, close connection */
         tcp_echoserver_connection_close(tpcb, es);
      }
      else
      {
        /* we're not done yet */
        /* acknowledge received packet */
        tcp_sent(tpcb, tcp_echoserver_sent);
        
        /* send remaining data*/
        tcp_echoserver_send(tpcb, es);
      }
      ret_err = ERR_OK;
    }   
    /* else : a non empty frame was received from client but for some reason err != ERR_OK */
    else if(err != ERR_OK)
    {
      /* free received pbuf*/
      if (p != NULL)
      {
        es->p = NULL;
        pbuf_free(p);
      }
      ret_err = err;
    }
    else if(es->state == ES_ACCEPTED)
    {
      /* first data chunk in p->payload */
      es->state = ES_RECEIVED;
      
      /* store reference to incoming pbuf (chain) */
      es->p = p;
      
      /* initialize LwIP tcp_sent callback function */
      tcp_sent(tpcb, tcp_echoserver_sent);
      
      /* send back the received data (echo) */
      tcp_echoserver_send(tpcb, es);
      
      ret_err = ERR_OK;
    }
    else if (es->state == ES_RECEIVED)
    {
      /* more data received from client and previous data has been already sent*/
      if(es->p == NULL)
      {
        es->p = p;
    
        /* send back received data */
        tcp_echoserver_send(tpcb, es);
      }
      else
      {
        struct pbuf *ptr;
  
        /* chain pbufs to the end of what we recv'ed previously  */
        ptr = es->p;
        pbuf_chain(ptr,p);
      }
      ret_err = ERR_OK;
    }
    else if(es->state == ES_CLOSING)
    {
      /* odd case, remote side closing twice, trash data */
      tcp_recved(tpcb, p->tot_len);
      es->p = NULL;
      pbuf_free(p);
      ret_err = ERR_OK;
    }
    else
    {
      /* unkown es->state, trash data  */
      tcp_recved(tpcb, p->tot_len);
      es->p = NULL;
      pbuf_free(p);
      ret_err = ERR_OK;
    }
    return ret_err;
  }
  
  /**
    * @brief  This function implements the tcp_err callback function (called
    *         when a fatal tcp_connection error occurs. 
    * @param  arg: pointer on argument parameter 
    * @param  err: not used
    * @retval None
    */
  static void tcp_echoserver_error(void *arg, err_t err)
  {
    struct tcp_echoserver_struct *es;
  
    LWIP_UNUSED_ARG(err);
  
    es = (struct tcp_echoserver_struct *)arg;
    if (es != NULL)
    {
      /*  free es structure */
      mem_free(es);
    }
  }
  
  /**
    * @brief  This function implements the tcp_poll LwIP callback function
    * @param  arg: pointer on argument passed to callback
    * @param  tpcb: pointer on the tcp_pcb for the current tcp connection
    * @retval err_t: error code
    */
  static err_t tcp_echoserver_poll(void *arg, struct tcp_pcb *tpcb)
  {
    err_t ret_err;
    struct tcp_echoserver_struct *es;
  
    es = (struct tcp_echoserver_struct *)arg;
    if (es != NULL)
    {
      if (es->p != NULL)
      {
        tcp_sent(tpcb, tcp_echoserver_sent);
        /* there is a remaining pbuf (chain) , try to send data */
        tcp_echoserver_send(tpcb, es);
      }
      else
      {
        /* no remaining pbuf (chain)  */
        if(es->state == ES_CLOSING)
        {
          /*  close tcp connection */
          tcp_echoserver_connection_close(tpcb, es);
        }
      }
      ret_err = ERR_OK;
    }
    else
    {
      /* nothing to be done */
      tcp_abort(tpcb);
      ret_err = ERR_ABRT;
    }
    return ret_err;
  }
  
  /**
    * @brief  This function implements the tcp_sent LwIP callback (called when ACK
    *         is received from remote host for sent data) 
    * @param  None
    * @retval None
    */
  static err_t tcp_echoserver_sent(void *arg, struct tcp_pcb *tpcb, u16_t len)
  {
    struct tcp_echoserver_struct *es;
  
    LWIP_UNUSED_ARG(len);
  
    es = (struct tcp_echoserver_struct *)arg;
    es->retries = 0;
    
    if(es->p != NULL)
    {
      /* still got pbufs to send */
      tcp_sent(tpcb, tcp_echoserver_sent);
      tcp_echoserver_send(tpcb, es);
    }
    else
    {
      /* if no more data to send and client closed connection*/
      if(es->state == ES_CLOSING)
        tcp_echoserver_connection_close(tpcb, es);
    }
    return ERR_OK;
  }
  
  
  /**
    * @brief  This function is used to send data for tcp connection
    * @param  tpcb: pointer on the tcp_pcb connection
    * @param  es: pointer on echo_state structure
    * @retval None
    */
  static void tcp_echoserver_send(struct tcp_pcb *tpcb, struct tcp_echoserver_struct *es)
  {
    struct pbuf *ptr;
    err_t wr_err = ERR_OK;
   
    while ((wr_err == ERR_OK) &&
           (es->p != NULL) && 
           (es->p->len <= tcp_sndbuf(tpcb)))
    {
      
      /* get pointer on pbuf from es structure */
      ptr = es->p;
  
      /* enqueue data for transmission */
      wr_err = tcp_write(tpcb, ptr->payload, ptr->len, 1);
      
      if (wr_err == ERR_OK)
      {
        u16_t plen;
        u8_t freed;
  
        plen = ptr->len;
       
        /* continue with next pbuf in chain (if any) */
        es->p = ptr->next;
        
        if(es->p != NULL)
        {
          /* increment reference count for es->p */
          pbuf_ref(es->p);
        }
        
       /* chop first pbuf from chain */
        do
        {
          /* try hard to free pbuf */
          freed = pbuf_free(ptr);
        }
        while(freed == 0);
       /* we can read more data now */
       tcp_recved(tpcb, plen);
     }
     else if(wr_err == ERR_MEM)
     {
        /* we are low on memory, try later / harder, defer to poll */
       es->p = ptr;
     }
     else
     {
       /* other problem ?? */
     }
    }
  }
  
  /**
    * @brief  This functions closes the tcp connection
    * @param  tcp_pcb: pointer on the tcp connection
    * @param  es: pointer on echo_state structure
    * @retval None
    */
  static void tcp_echoserver_connection_close(struct tcp_pcb *tpcb, struct tcp_echoserver_struct *es)
  {
    
    /* remove all callbacks */
    tcp_arg(tpcb, NULL);
    tcp_sent(tpcb, NULL);
    tcp_recv(tpcb, NULL);
    tcp_err(tpcb, NULL);
    tcp_poll(tpcb, NULL, 0);
    
    /* delete es structure */
    if (es != NULL)
    {
      mem_free(es);
    }  
    
    /* close tcp connection */
    tcp_close(tpcb);
  }
  
  #endif /* LWIP_TCP */
  