empop3c.c

C语言实现的一个简易的POP3服务器代码

/*
 *  Embedded POP3 Client
 *
 *  ./software/ch6/empop3c/empop3c.c
 *
 *  [e-mail]
 *
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include "empop3c.h"

#define POP3_PORT	110
#define SUCCESS		"+OK"
#define FAILURE		"-ERR"

#define MAX_LINE	512

static int sock=-1;
static int retIndex;
static char buffer[MAX_LINE+1];


/*
 *  dialog()
 *
 *  Perform a dialog transaction with the connected server.  In this
 *  dialog, a command may be sent but a response is always returned.
 *
 *  The user must pass in a character buffer containing an optional
 *  command (null string if no command is to be sent) and then the
 *  same string is used to collect the response.  
 *
 *  The function returns 0 on success, -1 on error.
 *
 */

static int dialog( int sock, char *command )
{
  int ret, len;

  if ( strlen(command) > 0 ) {
    len = strlen( command );
    if (write( sock, command, len ) != len) return -1;
  }

  ret = read( sock, command, MAX_LINE );
  if ( ret > 0 ) command[ret] = 0;
  else return -1;

  if (strncmp( command, "+OK", 3 )) return -1;

  return 0;
}


/*
 *  pop3cConnect()
 *
 *  Connect to a POP3 server using the server, username and password passed
 *  in to the function.
 *
 *  The number of messages is returned on success, -1 on failure.
 *
 */

int pop3cConnect ( char *pop3Server, char *user, char *pass )
{
  int result;
  struct sockaddr_in servaddr;

  sock = socket( AF_INET, SOCK_STREAM, 0 );

  bzero( (void *)&servaddr, sizeof(servaddr) );
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons( 110 );

  servaddr.sin_addr.s_addr = inet_addr( pop3Server );

  if ( servaddr.sin_addr.s_addr == 0xffffffff ) {
    struct hostent *hptr = (struct hostent *)gethostbyname( pop3Server );
    if ( hptr == NULL ) {
      return -1;
    } else {
      struct in_addr **addrs;
      addrs = (struct in_addr **)hptr->h_addr_list;
      memcpy( &servaddr.sin_addr, *addrs, sizeof(struct in_addr) );
    }
  }

  do {

    result = connect( sock, (struct sockaddr *)&servaddr, sizeof(servaddr) );

    if ( result < 0 ) break;

    /* Look for the salutation */
    buffer[0] = 0;
    result = dialog( sock, buffer );
    if ( result < 0 ) break;
    result = -1;
    
    /* Send the USER login */
    sprintf( buffer, "USER %s\n", user );
    result = dialog( sock, buffer );
    if ( result < 0 ) break;
    result = -1;

    /* Send the PASS login */
    sprintf( buffer, "PASS %s\n", pass );
    result = dialog( sock, buffer );
    if ( result < 0 ) break;
    result = -1;

    /* Finally, get the number of emails waiting */
    strcpy( buffer, "STAT\n" );
    result = dialog( sock, buffer );
    if ( result < 0 ) break;

    sscanf( buffer, "+OK %d", &result );

    retIndex = 1;

  } while (0);

  if ( result < 0 ) {
    close( sock );
    sock = -1;
  }

  return result;
}


/*
 *  pop3cRetrieve()
 *
 *  Retrieve a message from the pop3c connection.  This function is state
 *  driven and therefore, the first message is returned, and subsequent
 *  calls will return subsequent messages.  The user must perform a
 *  pop3cDelete in order to grab the next message.
 *
 *  The message size is returned on success, -1 on failure.
 *
 */

int pop3cRetrieve ( mail_t *mail, int totalLen )
{
  int result, i, bufIdx=0, state, stop, len;

  /* Send the Retrieve command */
  sprintf( buffer, "RETR %d\n", retIndex );
  result = dialog( sock, buffer );
  if ( result < 0 ) return -1;

  /* Skip the +OK response string and grab any data (end with CRLF) */
  len = strlen( buffer );
  for ( i = 0 ; i < len-1 ; i++ ) {
    if ( (buffer[i] == 0x0d) && (buffer[i+1] == 0x0a) ) {
      len -= i-2;
      memmove( mail->email, &buffer[i+2], len );
      break;
    }
  }

  state = stop = 0;
 
  while (!stop) {

    if (bufIdx+len > totalLen - 80) break;

    /* Search for the end-of-mail indicator in the current buffer */
    for ( i = bufIdx ; i < bufIdx+len ; i++ ) {
      if      ( (state == 0) && (mail->email[i] == 0x0d) ) state = 1;
      else if ( (state == 1) && (mail->email[i] == 0x0a) ) state = 2;
      else if ( (state == 2) && (mail->email[i] == 0x0d) ) state = 1;
      else if ( (state == 2) && (mail->email[i] ==  '.') ) state = 3;
      else if ( (state == 3) && (mail->email[i] == 0x0d) ) state = 4;
      else if ( (state == 4) && (mail->email[i] == 0x0a) ) { stop = 1; break; }
      else state = 0;
    }

    bufIdx += (i-bufIdx);

    if (!stop) {

      len = read( sock, &mail->email[bufIdx], (totalLen-bufIdx) );

      if ( (len <= 0) || (bufIdx+len > totalLen) ) {
        break;
      }

    }

  }

  bufIdx -= 3;
  mail->email[bufIdx] = 0;
  mail->email_len = bufIdx;

  return bufIdx;
}


/*
 *  pop3cDelete()
 *
 *  Delete a message from the pop3c connection.  The message deleted is the
 *  last retrieved from the POP3 server.  This function also increments the
 *  message index so that the next message may be retrieved.
 *
 *  A 0 is returned on success, -1 on failure.
 *
 */

int pop3cDelete ( void )
{
  int result;

  /* Send the USER login */
  sprintf( buffer, "DELE %d\n", retIndex++ );
  result = dialog( sock, buffer );
  if ( result < 0 ) return -1;
  result = -1;

  return( result );
}


/*
 *  pop3cDisconnect()
 *
 *  Disconnect from the current POP3 connection.
 *
 *  A 0 is returned on success, -1 on failure.
 *
 */

int pop3cDisconnect ( void )
{
  int result;

  strcpy( buffer, "QUIT\n" );
  result = dialog( sock, buffer );
  if ( result < 0 ) return -1;
  return 0;
}

/*
 *  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.
 */