udgramsrv.c

这是有名的＜＜嵌入式系统TCP/IP应用层协议＞＞,M.Tim Jones 著

/*
 *  Daytime Server using datagram sockets (UDP)
 *
 *  ./software/apdxA/daytime/u_dgram/udgramsrv.c
 *
 *  [e-mail]
 *
 */

#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>

#define MAX_BUFFER		128
#define DAYTIME_SERVER_PORT	45000

int main ( void )
{
  int serverFd, fromlen, msglen;
  struct sockaddr_in servaddr, from;
  char timebuffer[MAX_BUFFER+1];
  time_t currentTime;

  serverFd = socket(AF_INET, SOCK_DGRAM, 0);

  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(DAYTIME_SERVER_PORT);

  bind(serverFd, (struct sockaddr *)&servaddr, sizeof(servaddr));

  while ( 1 ) {

    fromlen = sizeof(from);
    msglen = recvfrom(serverFd, &timebuffer, MAX_BUFFER, 0, &from, &fromlen);

    if (msglen >= 0) {

      currentTime = time(NULL);
      snprintf(timebuffer, MAX_BUFFER, "%s\n", ctime(&currentTime));

      sendto(serverFd, timebuffer, strlen(timebuffer), 0,
              (struct sockaddr *)&from, fromlen);

      currentTime = time(NULL);
      snprintf(timebuffer, MAX_BUFFER, "%s\n", ctime(&currentTime));

      sendto(serverFd, timebuffer, strlen(timebuffer), 0,
              (struct sockaddr *)&from, fromlen);

    }

  }

}

/*
 *  Copyright (c) 2002 Charles River Media.  All rights reserved.
 * 
 *  Redistribution and use in source and binary forms, with or 
 *  without modification, is hereby granted without fee 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.  Neither the name of Charles River Media nor the names of 
 *        its contributors may be used to endorse or promote products 
 *        derived from this software without specific prior 
 *        written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY CHARLES RIVER MEDIA AND CONTRIBUTERS 
 * 'AS IS' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS 
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL CHARLES
 * RIVER MEDIA OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 
 * INCIDENTAL, SPECIAL, EXEMPLARAY, 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.
 */