nextport.c

用于嵌入式系统的TCP/IP协议栈

/***********************************************************************/
/*                                                                     */
/*   Module:  tcp_ip/tcp/tcpsock.c                                     */
/*   Release: 2001.3                                                   */
/*   Version: 99.0                                                     */
/*   Purpose: TCP API Support                                          */
/*                                                                     */
/*---------------------------------------------------------------------*/
/*                                                                     */
/*               Copyright 1999, Blunk Microsystems                    */
/*                      ALL RIGHTS RESERVED                            */
/*                                                                     */
/*   Licensees have the non-exclusive right to use, modify, or extract */
/*   this computer program for software development at a single site.  */
/*   This program may be resold or disseminated in executable format   */
/*   only. The source code may not be redistributed or resold.         */
/*                                                                     */
/***********************************************************************/
#include "../tcp_ipp.h"

/***********************************************************************/
/* Global Function Definitions                                         */
/***********************************************************************/

/***********************************************************************/
/* TcpNextPort: Return next unused TCP local port number               */
/*                                                                     */
/***********************************************************************/
ui16 TcpNextPort(void)
{
  static ui16 port_num;
  CircLink *link;
  ui16 netorder;
  int i;

  for (i = 0; i < (HI_PORT_NUM - LO_PORT_NUM); ++i)
  {
    /*-----------------------------------------------------------------*/
    /* Increment the port number, wrapping around as necessary.        */
    /*-----------------------------------------------------------------*/
    ++port_num;
    if ((port_num < LO_PORT_NUM) || (port_num > HI_PORT_NUM))
      port_num = LO_PORT_NUM;

    /*-----------------------------------------------------------------*/
    /* Check every open TCP socket.                                    */
    /*-----------------------------------------------------------------*/
    netorder = htons(port_num);
    for (link = TcpLruList.next_bck;; link = link->next_bck)
    {
      /*---------------------------------------------------------------*/
      /* Port number unique if end of socket list reached.             */
      /*---------------------------------------------------------------*/
      if (link == &TcpLruList)
        return netorder;

      /*---------------------------------------------------------------*/
      /* Break to try another number if already in use.                */
      /*---------------------------------------------------------------*/
      if (((SOCKET)link)->local.sin_port == netorder)
        break;
    }

  }
  return 0;
}