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The C and C++ Include Header Files

cat -n /usr/include/netinet/in_systm.h

     1	/* System specific type definitions for networking code.
     2	   Copyright (C) 1997-2026 Free Software Foundation, Inc.
     3	   This file is part of the GNU C Library.
     4	
     5	   The GNU C Library is free software; you can redistribute it and/or
     6	   modify it under the terms of the GNU Lesser General Public
     7	   License as published by the Free Software Foundation; either
     8	   version 2.1 of the License, or (at your option) any later version.
     9	
    10	   The GNU C Library is distributed in the hope that it will be useful,
    11	   but WITHOUT ANY WARRANTY; without even the implied warranty of
    12	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13	   Lesser General Public License for more details.
    14	
    15	   You should have received a copy of the GNU Lesser General Public
    16	   License along with the GNU C Library; if not, see
    17	   <https://www.gnu.org/licenses/>.  */
    18	
    19	#ifndef _NETINET_IN_SYSTM_H
    20	#define _NETINET_IN_SYSTM_H 1
    21	
    22	#include <sys/types.h>
    23	#include <stdint.h>
    24	
    25	__BEGIN_DECLS
    26	
    27	/*
    28	 * Network order versions of various data types. Unfortunately, BSD
    29	 * assumes specific sizes for shorts (16 bit) and longs (32 bit) which
    30	 * don't hold in general. As a consequence, the network order versions
    31	 * may not reflect the actual size of the native data types.
    32	 */
    33	
    34	typedef uint16_t n_short;      /* short as received from the net */
    35	typedef uint32_t n_long;       /* long as received from the net  */
    36	typedef uint32_t n_time;       /* ms since 00:00 GMT, byte rev   */
    37	
    38	__END_DECLS
    39	
    40	#endif /* netinet/in_systm.h */