NAME
shutdown — shut down a socket
SYNOPSIS
#include <sys/socket.h>
int shutdown(int s, int how);
DESCRIPTION
The
shutdown()
system call is used to shut down a socket.
In the case of a full-duplex connection,
shutdown()
can be used to either partially or fully shut down the socket,
depending upon the value of
how.
- how
Interpretation
- SHUT_RD or 0
Further receives are disallowed
- SHUT_WR or 1
Further sends are disallowed
- SHUT_RDWR or 2
Further sends and receives are disallowed
The
s
parameter is a socket descriptor for the socket to be shut down.
Once the socket has been shut down for receives, all further
recv()
calls return an end-of-file condition.
A socket that has been shut down for sending causes further
send()
calls to return an
EPIPE
error and send the
SIGPIPE
signal.
After a socket has been fully shut down, operations other than
recv()
and
send()
return appropriate errors,
and the only other thing that can be done to the socket is a
close().
Multiple shutdowns on a connected socket and shutdowns on a socket
that is not connected may not return errors.
A
shutdown()
on a connectionless socket, such as
SOCK_DGRAM,
only marks the socket as unable to do further
send()
or
recv()
calls, depending upon the value of
how.
Once this type of socket has been disabled
for both sending and receiving data,
it becomes fully shut down.
For
SOCK_STREAM
sockets, if
how
is
1 or
2,
the connection begins to be closed gracefully
in addition to the normal actions.
However, the
shutdown()
call does not wait for the completion of the graceful disconnection.
The disconnection is complete
when both sides of the connection have done a
shutdown()
with
how
equal to
1 or
2.
Once the connection has been completely terminated,
the socket becomes fully shut down.
The
SO_LINGER
option (see
socket(2))
does not have any meaning for the
shutdown()
call, but does for the
close()
call.
For more information on how the
close()
call interacts with sockets, see
socket(2).
If a
shutdown()
is performed on a
SOCK_STREAM
socket that has a
listen()
pending on it, that socket becomes fully shut down when
how
= 1.
AF_CCITT only
The
how
parameter behaves differently if the socket is of the
AF_CCITT
address family.
If
how
is set to
0
the specified socket can no longer receive data.
The
SVC
is not cleared and remains intact.
However, if data is subsequently received on the
SVC,
it is cleared.
The connection is not completely down until either side executes a
close()
or
shutdown()
with
how
set to
1 or
2.
If
how
is set to
1
or
2,
the
SVC
can no longer send or receive data and the
SVC
is cleared.
The socket's resources are maintained
so that data arriving prior to the
shutdown()
call can still be read.
RETURN VALUE
Upon successful completion,
shutdown()
returns 0; otherwise it returns -1 and
errno
is set to indicate the error.
ERRORS
shutdown()
fails if any of the following conditions are encountered:
- EBADF
s
is not a valid file descriptor.
- ENOPROTOOPT
The remote system or an intermediate system in the communications path
does not support a protocol option sent by the local system.
This option may have been set using a
getsockopt
or
setsockopt()
call, or set as a system parameter.
- ENOTSOCK
s
is a valid file descriptor, but it is not a socket.
- EINVAL
HP-UX BSD Sockets only.
The specified socket is not connected.
- ENOTCONN
X/Open Sockets only.
The specified socket is not connected.
- EINVAL
X/Open Sockets only.
The
how
argument is invalid.
WARNINGS
Linking binary objects compiled to
X/Open Sockets
specification and binary objects compiled to
HP-UX BSD Sockets
specification to the same executable may result in unexpected behavior,
including application abnormal termination and unexpected socket errors.
See
xopen_networking(7)
for details and remedy.
FUTURE DIRECTION
Currently, the default behavior is the
HP-UX BSD Sockets;
however, it might be changed to
X/Open Sockets
in a future release.
At that time, any
HP-UX BSD Sockets
behavior that is incompatible with
X/Open Sockets
might be obsoleted.
Applications that conform to the
X/Open specification now
will avoid migration problems (see
xopen_networking(7)).
AUTHOR
shutdown()
was developed by HP and the University of California, Berkeley.
STANDARDS CONFORMANCE
shutdown(): XPG4, UNIX 95, UNIX 03
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