udp(ADMP)
udp --
Internet User Datagram Protocol
Syntax
Programmer's interface:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
s = socket(AF_INET, SOCK_DGRAM, 0);
#include <paths.h>
#include <fcntl.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
fd = open(_PATH_UDP, flags);
Description
UDP is a simple, unreliable datagram protocol
that is used to support the SOCK_DGRAM
abstraction for the Internet protocol family.
UDP sockets are connectionless, and are normally
used with the sendto and recvfrom
calls; the
connect(SSC)
call may also be used to fix the destination for future
packets (in which case the
recv(SSC),
or
read(S)
and
send(SSC),
or
write(S)
system/library calls may be used). In addition,
UDP is available as TLI connectionless
transport via the special file /dev/inet/udp.
UDP address formats are identical to those used
by TCP. In particular, UDP provides a
port identifier in addition to the normal Internet address
format. Note that the UDP port space is separate
from the TCP port space (that is, a UDP
port may not be ``connected'' to a TCP
port). In addition, broadcast packets may be sent
(assuming the underlying network supports this) by using a
reserved ``broadcast address''; this address is
network interface dependent.
Options at the IP transport level may be used with
UDP; see
ip(ADMP).
The UDP driver may also be accessed by opening it
directly. Network related statistics can be obtained by
issuing the following ioctls, defined in
<netinet/ip_var.h> and
<netinet/udp_var.h>, to the driver:
SIOCSMGMT-
to set the inpcb associated with the end-point as
a management inpcb (to distinguish it from
others, when network statistics are gathered) and link it
in the list of management inpcbs.
SIOCGUDPSTATS-
to extract UDP statistics. The structure
udpstat is passed as an argument to the
I_STR ioctl call.
STIOCGUDB-
to fetch the entire UDP table. It is a
transparent ioctl and functions similar to
STIOCBTCB, see
tcp(ADMP).
Diagnostics
A socket operation may fail with one of the following errors returned:
[EISCONN]-
when trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected
[ENOTCONN]-
when trying to send a datagram, but no destination address
is specified, and the socket hasn't been
connected
[ENOSR]-
when the system runs out of memory for an internal data structure
[EADDRINUSE]-
when an attempt is made to create a socket with a port which has
already been allocated
[EADDRNOTAVAIL]-
when an attempt is made to create a socket with a network address
for which no network interface exists.
An ioctl operation may fail with the
errno set to one of the following:
[EINVAL]-
when no argument/NULL argument is passed to the
driver, or when the command in the copyresp
structure is not valid, or when the
ioc_count
is
not TRANSPARENT for a transparent ioctl
[ENXIO]-
when the associated file descriptor is no longer open/valid.
Files
/dev/inet/udp
See also
Intro(ADMP),
getsockopt(SSC),
inet(ADMP),
ip(ADMP),
recv(SSC),
send(SSC),
socket(SSC),
streamio(M),
tcp(ADMP)
Standards conformance
udp is conformant with:
RFC 768 (STD 6), RFC 1122 (STD 7)
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003