HP-UX Reference (11i v2 07/12) - 2 System Calls (vol 5)

s
shutdown(2) shutdown(2)
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
1or2, 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 1or2
. 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 1or2.
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.
SCTP Only:
SCTP differs from TCP in that it does not have half closed semantics. Hence the shutdown() call for
SCTP is an approximation of the TCP shutdown() call and solves some different problems. Full
TCP-compatibility is not provided, so developers porting TCP applications to SCTP may need to re-code sec-
tions that use shutdown() . Note that it is possible to achieve the same results as half closed in SCTP
using SCTP streams.
These are the possible SCTP shutdown() operations:
SHUT_RD Disables further receive operations. No SCTP protocol action is taken.
SHUT_WR Disables further send operations and initiates the SCTP shutdown sequence.
SHUT_RDWR Disables further send and receive operations and initiates the SCTP shutdown
sequence.
The major difference between SCTP and TCP shutdown() is that SCTP SHUT_WR initiates immediate
and full protocol shutdown, whereas TCP SHUT_WR causes TCP to go into the half closed state. SHUT_RD
behaves the same for SCTP as TCP. The purpose of SCTP SHUT_WR is to close the SCTP association while
HP-UX 11i Version 2: December 2007 Update − 1 − Hewlett-Packard Company 403