1.\" $NetBSD: udp.4,v 1.5 1999/03/16 01:19:18 garbled 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)udp.4 8.1 (Berkeley) 6/5/93 35.\" 36.Dd June 5, 1993 37.Dt UDP 4 38.Os 39.Sh NAME 40.Nm udp 41.Nd Internet User Datagram Protocol 42.Sh SYNOPSIS 43.Fd #include <sys/socket.h> 44.Fd #include <netinet/in.h> 45.Ft int 46.Fn socket AF_INET SOCK_DGRAM 0 47.Sh DESCRIPTION 48.Tn UDP 49is a simple, unreliable datagram protocol which is used 50to support the 51.Dv SOCK_DGRAM 52abstraction for the Internet 53protocol family. 54.Tn UDP 55sockets are connectionless, and are 56normally used with the 57.Xr sendto 2 58and 59.Xr recvfrom 2 60calls, though the 61.Xr connect 2 62call may also be used to fix the destination for future 63packets (in which case the 64.Xr recv 2 65or 66.Xr read 2 67and 68.Xr send 2 69or 70.Xr write 2 71system calls may be used). 72.Pp 73.Tn UDP 74address formats are identical to those used by 75.Tn TCP . 76In particular 77.Tn UDP 78provides a port identifier in addition 79to the normal Internet address format. 80Note that the 81.Tn UDP 82port 83space is separate from the 84.Tn TCP 85port space (i.e. a 86.Tn UDP 87port 88may not be 89.Dq connected 90to a 91.Tn TCP 92port). 93In addition broadcast packets may be sent (assuming the underlying 94network supports this) by using a reserved 95.Dq broadcast address ; 96this address 97is network interface dependent. 98.Pp 99Options at the 100.Tn IP 101transport level may be used with 102.Tn UDP ; 103see 104.Xr ip 4 . 105.Sh DIAGNOSTICS 106A socket operation may fail with one of the following errors returned: 107.Bl -tag -width [EADDRNOTAVAIL] 108.It Bq Er EISCONN 109when trying to establish a connection on a socket which 110already has one, or when trying to send a datagram with the destination 111address specified and the socket is already connected; 112.It Bq Er ENOTCONN 113when trying to send a datagram, but 114no destination address is specified, and the socket hasn't been 115connected; 116.It Bq Er ENOBUFS 117when the system runs out of memory for 118an internal data structure; 119.It Bq Er EADDRINUSE 120when an attempt 121is made to create a socket with a port which has already been 122allocated; 123.It Bq Er EADDRNOTAVAIL 124when an attempt is made to create a socket with a network address 125for which no network interface exists. 126.El 127.Sh SEE ALSO 128.Xr getsockopt 2 , 129.Xr recv 2 , 130.Xr send 2 , 131.Xr socket 2 , 132.Xr intro 4 , 133.Xr inet 4 , 134.Xr ip 4 135.Rs 136.%R RFC 137.%N 768 138.%D August 28, 1980 139.%T "User Datagram Protocol" 140.Re 141.Rs 142.%R RFC 143.%N 1122 144.%D October 1989 145.%T "Requirements for Internet Hosts -- Communication Layers" 146.Re 147.Sh HISTORY 148The 149.Nm 150protocol appeared in 151.Bx 4.2 . 152