1.\" $OpenBSD: htonl.3,v 1.4 2016/03/10 08:42:26 jmc Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: March 10 2016 $ 31.Dt HTONL 3 32.Os 33.Sh NAME 34.Nm htonl , 35.Nm htons , 36.Nm ntohl , 37.Nm ntohs 38.Nd convert values between host and network byte orderings 39.Sh SYNOPSIS 40.In arpa/inet.h 41.Ft uint32_t 42.Fn htonl "uint32_t host32" 43.Ft uint16_t 44.Fn htons "uint16_t host16" 45.Ft uint32_t 46.Fn ntohl "uint32_t net32" 47.Ft uint16_t 48.Fn ntohs "uint16_t net16" 49.Sh DESCRIPTION 50These routines convert 16 and 32-bit quantities between different 51byte orderings. 52.Pp 53The 54.Fn htonl 55and 56.Fn htons 57functions convert quantities from host to network byte order while the 58.Fn ntohl 59and 60.Fn ntohs 61functions convert in the other direction. 62.Pp 63The last letter 64.Pf ( Sq s 65or 66.Sq l ) 67is a mnemonic 68for the traditional names for such quantities, 69.Li short 70and 71.Li long , 72respectively. 73Today, the C concept of 74.Li short 75and 76.Li long 77integers need not coincide with this traditional misunderstanding. 78On machines which have a byte order which is the same as the network 79order, routines are defined as null macros. 80.Pp 81These routines are most often used in conjunction with Internet 82addresses and ports as returned by 83.Xr gethostbyname 3 84and 85.Xr getservent 3 . 86.Sh SEE ALSO 87.Xr gethostbyname 3 , 88.Xr getservent 3 89.Sh STANDARDS 90The 91.Fn htonl , 92.Fn htons , 93.Fn ntohl , 94and 95.Fn ntohs 96functions conform to 97.St -p1003.1 . 98.Sh HISTORY 99These functions appeared in 100.Bx 4.2 . 101.Sh BUGS 102On the alpha, amd64, i386, and some mips and arm architectures, 103bytes are handled backwards from most everyone else in the world. 104This is not expected to be fixed in the near future. 105