projects / unix-history / blame
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|---|---|---|
| c82418af KM |
1 | .\" Copyright (c) 1983 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| 95f51977 | 5 | .\" @(#)udp.4p 6.2 (Berkeley) 5/16/86 |
| c82418af | 6 | .\" |
| 95f51977 | 7 | .TH UDP 4P "May 16, 1986" |
| c82418af KM |
8 | .UC 5 |
| 9 | .SH NAME | |
| 10 | udp \- Internet User Datagram Protocol | |
| 11 | .SH SYNOPSIS | |
| 12 | .B #include <sys/socket.h> | |
| 13 | .br | |
| 14 | .B #include <netinet/in.h> | |
| 15 | .PP | |
| 16 | .B s = socket(AF_INET, SOCK_DGRAM, 0); | |
| 17 | .SH DESCRIPTION | |
| 18 | UDP is a simple, unreliable datagram protocol which is used | |
| 19 | to support the SOCK_DGRAM abstraction for the Internet | |
| 20 | protocol family. UDP sockets are connectionless, and are | |
| 21 | normally used with the | |
| 22 | .I sendto | |
| 23 | and | |
| 24 | .IR recvfrom | |
| 25 | calls, though the | |
| 26 | .IR connect (2) | |
| 27 | call may also be used to fix the destination for future | |
| 28 | packets (in which case the | |
| 29 | .IR recv (2) | |
| 30 | or | |
| 31 | .IR read (2) | |
| 32 | and | |
| 33 | .IR send (2) | |
| 34 | or | |
| 35 | .IR write(2) | |
| 36 | system calls may be used). | |
| 37 | .PP | |
| 38 | UDP address formats are identical to those used by | |
| 39 | TCP. In particular UDP provides a port identifier in addition | |
| 40 | to the normal Internet address format. Note that the UDP port | |
| 41 | space is separate from the TCP port space (i.e. a UDP port | |
| 42 | may not be \*(lqconnected\*(rq to a TCP port). In addition broadcast | |
| 43 | packets may be sent (assuming the underlying network supports | |
| 44 | this) by using a reserved \*(lqbroadcast address\*(rq; this address | |
| 45 | is network interface dependent. | |
| 7787ae36 MK |
46 | .PP |
| 47 | Options at the IP transport level may be used with UDP; see | |
| 48 | .IR ip (4P). | |
| c82418af KM |
49 | .SH DIAGNOSTICS |
| 50 | A socket operation may fail with one of the following errors returned: | |
| 51 | .TP 15 | |
| 52 | [EISCONN] | |
| 53 | when trying to establish a connection on a socket which | |
| 54 | already has one, or when trying to send a datagram with the destination | |
| 55 | address specified and the socket is already connected; | |
| 56 | .TP 15 | |
| 57 | [ENOTCONN] | |
| 58 | when trying to send a datagram, but | |
| 59 | no destination address is specified, and the socket hasn't been | |
| 60 | connected; | |
| 61 | .TP 15 | |
| 62 | [ENOBUFS] | |
| 63 | when the system runs out of memory for | |
| 64 | an internal data structure; | |
| 65 | .TP 15 | |
| 66 | [EADDRINUSE] | |
| 67 | when an attempt | |
| 68 | is made to create a socket with a port which has already been | |
| 69 | allocated; | |
| 70 | .TP 15 | |
| 71 | [EADDRNOTAVAIL] | |
| 72 | when an attempt is made to create a | |
| 73 | socket with a network address for which no network interface | |
| 74 | exists. | |
| 75 | .SH SEE ALSO | |
| 7787ae36 | 76 | getsockopt(2), recv(2), send(2), socket(2), intro(4N), inet(4F), ip(4P) |