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.\"     @(#)cltp.4	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt CLTP 4
.Os
.Sh NAME
.Nm cltp
.Nd
.Tn ISO
Connectionless Transport Protocol
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Fd #include <netiso/iso.h>
.Ft int
.Fn socket AF_ISO SOCK_DGRAM 0
.Sh DESCRIPTION
.Tn CLTP
is a simple, unreliable datagram protocol which is accessed
via the
.Dv SOCK_DGRAM
abstraction for the
.Tn ISO
protocol family.
.Tn CLTP
sockets are connectionless, and are
normally used with the
.Xr sendto
and
.Xr recvfrom
calls, though the
.Xr connect 2
call may also be used to fix the destination for future
packets (in which case the 
.Xr recv 2
or
.Xr read 2
and 
.Xr send 2
or
.Xr write 2
system calls may be used).
.Pp
.Tn CLTP
address formats are identical to those used by TP.
In particular
.Tn CLTP
provides a service selector in addition
to the normal
.Tn ISO NSAP .
Note that the
.Tn CLTP
selector
space is separate from the TP selector space (i.e. a
.Tn CLTP
selector
may not be
.Dq connected
to a TP selector).
.Pp
Options at the
.Tn CLNP
network level may be used with
.Tn CLTP ;
see
.Xr clnp 4 .
.Sh DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width [EADDRNOTAVAIL]
.It Bq Er 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;
.It Bq Er ENOTCONN
when trying to send a datagram, but
no destination address is specified, and the socket hasn't been
connected;
.It Bq Er ENOBUFS
when the system runs out of memory for
an internal data structure;
.It Bq Er EADDRINUSE
when an attempt
is made to create a socket with a selector which has already been
allocated;
.It Bq Er EADDRNOTAVAIL
when an attempt is made to create a 
socket with a network address for which no network interface
exists.
.El
.Sh SEE ALSO
.Xr getsockopt 2 ,
.Xr recv 2 ,
.Xr send 2 ,
.Xr socket 2 ,
.Xr intro 4 ,
.Xr iso 4 ,
.Xr clnp 4