c发邮件

 /* base64编码 */
 static const char* base64_enc_map = \
                                     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 int base64_encode( char* dst, size_t* dlen, const unsigned char* src, size_t slen )
 {
     size_t i, n;
     int C1, C2, C3;
     char* p;

     if ( slen ==  )
     {
         return ;
     }

     n = ( slen <<  ) / ;

     switch ( ( slen <<  ) - ( n *  ) )
     {
         case  :
             n += ;
             break;
         case  :
             n += ;
             break;
         default:
             break;
     }

     if ( *dlen < n +  )
     {
         *dlen = n + ;
         return -;
     }

     n = ( slen /  ) * ;
     for ( i = , p = dst; i < n; i +=  )
     {
         C1 = *src++;
         C2 = *src++;
         C3 = *src++;
         *p++ = base64_enc_map[( C1 >>  ) & 0x3F];
         *p++ = base64_enc_map[( ( ( C1 &   ) <<  ) + ( C2 >>  ) ) & 0x3F];
         *p++ = base64_enc_map[( ( ( C2 &  ) <<  ) + ( C3 >>  ) ) & 0x3F];
         *p++ = base64_enc_map[C3 & 0x3F];
     }

     if ( i < slen )
     {
         C1 = *src++;
         C2 = ( ( i +  ) < slen ) ? *src++ : ;
         *p++ = base64_enc_map[( C1 >>  ) & 0x3F];
         *p++ = base64_enc_map[( ( ( C1 &  ) <<  ) + ( C2 >>  ) ) & 0x3F];
         ( i +  ) < slen ? ( *p++ = base64_enc_map[( ( C2 &  ) <<  ) & 0x3F] ) : ( *p++ = '=' );
         *p++ = '=';
     }

     *dlen = p - dst;
     *p = ;

     return ;
 }

 /* 主动连接 */
 static SOCKET tcp_connect( const char* host, unsigned short port = , int msec =  )
 {
     int ret;
     SOCKET fd;
     struct sockaddr_in sin;
     struct hostent* h;
     unsigned long ul;
     struct timeval tv;
     struct linger lg;
     int nodelay;
     fd_set fdset;

     /* 填充服务器地址 */
     memset( &sin, , sizeof( sin ) );
     sin.sin_family = AF_INET;
     if ( ( h = gethostbyname( host ) ) == NULL || h->h_addrtype != AF_INET )
     {
         return INVALID_SOCKET;
     }
     memcpy( &sin.sin_addr.S_un.S_addr, h->h_addr, h->h_length );
     sin.sin_port = htons( port );

     /* 建socket */
     if ( ( fd = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP ) ) ==  INVALID_SOCKET )
     {
         return INVALID_SOCKET;
     }

     /* 设置非阻塞 */
     ul = ;
     if ( ioctlsocket( fd, FIONBIO, &ul ) !=  )
     {
         closesocket( fd );
         return INVALID_SOCKET;
     }

     /* 主动连接 */
     if ( connect( fd, ( const struct sockaddr* ) &sin, sizeof( sin ) ) !=  )
     {
         FD_ZERO( &fdset );
         FD_SET( fd, &fdset );

         memset( &tv, , sizeof( tv ) );
         tv.tv_sec = msec / ;
         tv.tv_usec = ( msec %  ) * ;

         /* 超时或报错 */
         if ( select( fd + , , &fdset, , &tv ) !=  )
         {
             closesocket( fd );
             return INVALID_SOCKET;
         }
     }

     /* 置为阻塞 */
     ul = ;
     ret = ioctlsocket( fd, FIONBIO, &ul );
     assert( ret ==  );

     /*消除滞留*/
     memset( &lg, , sizeof( lg ) );
     ret = setsockopt( fd, SOL_SOCKET, SO_LINGER, ( const char* ) &lg, sizeof( lg ) );
     assert( ret ==  );

     /*禁用合并*/
     nodelay = ;
     ret = setsockopt( fd, IPPROTO_TCP, TCP_NODELAY, ( const char* ) &nodelay, sizeof( nodelay ) );
     assert( ret ==  );

     return fd;
 }

 #define RECV(fd, buff, suc) do { \
         if (recv( (fd), (buff), sizeof( (buff) ),  ) <=  || \
                 memcmp((buff), (suc), )) \
         { \
             closesocket((fd)); \
             return -; \
         } \
     }while()

 #define SEND(fd, buff, len) do { \
         register size_t i = (len); \
         if (send( (fd), (buff), i,  ) < (int)i) \
         { \
             closesocket((fd)); \
             return -; \
         } \
     }while()

 /* 发邮件 */
 int send_mail( const char* server,
                const char* user, const char* pwd, \
                const char* sender, const char* receiver, \
                const char* str, const unsigned char* data, size_t datalen )
 {
     SOCKET fd;
     char buff[];
     size_t len;
     size_t pos;

     /* 连接SMTP服务器 */
     fd = tcp_connect( server );
     if ( fd == INVALID_SOCKET )
     {
         ::MessageBox( NULL, "无法连接服务器，请检查网络设备！", "错误", MB_OK );
         return -;
     }

     /* 邮件问答 */
     RECV( fd, buff, "" );

     sprintf( buff, "HELO %s\r\n", server );
     SEND( fd, buff, strlen( buff ) );
     RECV( fd, buff, "" );

     /* 登录过程 */
     SEND( fd, "AUTH LOGIN\r\n",  ); /* 请求登录 */
     RECV( fd, buff, "" );

     len = sizeof( buff );
     base64_encode( buff, &len, ( const unsigned char* )user, strlen( user ) );
     strcat( buff, "\r\n" );
     SEND( fd, buff, len +  ); /* 用户名 */
     RECV( fd, buff, "" );

     len = sizeof( buff );
     base64_encode( buff, &len, ( const unsigned char* )pwd, strlen( pwd ) );
     strcat( buff, "\r\n" );
     SEND( fd, buff, len +  ); /* 密码 */
     RECV( fd, buff, "" );

     /* 邮件头 */
     sprintf( buff, "MAIL FROM:<%s>\r\n", sender );
     SEND( fd, buff, strlen( buff ) ); /* 发送者 */
     RECV( fd, buff, "" ); /* 250 Ok... */

     sprintf( buff, "RCPT TO:<%s>\r\n", receiver );
     SEND( fd, buff, strlen( buff ) ); /* 接收者 */
     RECV( fd, buff, "" );

     SEND( fd, "DATA\r\n",  ); /* 请求发送数据 */
     RECV( fd, buff, "" );

     sprintf( buff, "From:\"javadotest\"<%s>\r\n"
              "To:\"javado\"<%s>\r\n"
              "Subject:邮件标题\r\n"
              "MIME-Version: 1.0\r\n"
              "Content-Type: multipart/mixed; boundary=\"o0o0o0o0o\"\r\n\r\n", \
              sender, receiver );
     SEND( fd, buff, strlen( buff ) );

     /* 发送邮件内容 */
     sprintf( buff, "--o0o0o0o0o\r\n"
              "Content-Type: text/plain; charset=\"gb2312\"\r\n\r\n"
              "%s\r\n\r\n", str );
     SEND( fd, buff, strlen( buff ) );

     /* 发送附件 */
     strcpy( buff, "--o0o0o0o0o\r\n"
             "Content-Type: application/octet-stream; name=\"附件.doc\"\r\n"
             "Content-Transfer-Encoding: base64\r\n"
             "Content-Disposition: attachment; filename=\"附件.doc\"\r\n\r\n" );
     SEND( fd, buff, strlen( buff ) );
     if ( datalen >  )
     {
         for ( pos = ; pos < datalen; )
         {
             len = sizeof( buff );
             memset( buff, , sizeof( buff ) );

             if ( datalen - pos >=  )
             {
                 base64_encode( buff, &len, data + pos,  );
                 strcat( buff, "\r\n" );
                 SEND( fd, buff,  );
                 pos += ;
             }
             else
             {
                 base64_encode( buff, &len, data + pos, datalen - pos );
                 strcat( buff, "\r\n" );
                 SEND( fd, buff, strlen( buff ) );
                 break;
             }
         }
     }

     /* 完成发送 */
     SEND( fd, "--o0o0o0o0o--\r\n.\r\nQUIT\r\n",  ); /* 请求退出 */
     RECV( fd, buff, "" ); /* 250 Ok */

     closesocket( fd );
     return ;
 }