Manual Pages  — SHUTDOWN

shutdown – disable sends and/or receives on a socket

LIBRARY SYNOPSIS DESCRIPTION IMPLEMENTATION NOTES RETURN VALUES ERRORS SEE ALSO STANDARDS HISTORY AUTHORS BUGS

Standard C Library (libc, -lc)

#include <sys/types.h>

#include <sys/socket.h>

int
shutdown(int s, int how);

The shutdown() system call disables sends or receives on a socket. The how argument specifies the type of shutdown. Possible values are:

SHUT_RD	Further receives will be disallowed.
SHUT_WR	Further sends will be disallowed. This may cause actions specific to the protocol family of the socket s to happen; see IMPLEMENTATION NOTES.
SHUT_RDWR
	Further sends and receives will be disallowed. Implies SHUT_WR.

If the file descriptor s is associated with a SOCK_STREAM socket, all or part of the full-duplex connection will be shut down.

The following protocol specific actions apply to the use of SHUT_WR (and potentially also SHUT_RDWR), based on the properties of the socket associated with the file descriptor s.

Domain	Type	Protocol	Action
PF_INET	SOCK_DGRAM	IPPROTO_SCTP	Failure, as socket is not connected.
PF_INET	SOCK_DGRAM	IPPROTO_UDP	Failure, as socket is not connected.
PF_INET	SOCK_STREAM	IPPROTO_SCTP	Send queued data and tear down association.
PF_INET	SOCK_STREAM	IPPROTO_TCP	Send queued data, wait for ACK, then send FIN.
PF_INET6	SOCK_DGRAM	IPPROTO_SCTP	Failure, as socket is not connected.
PF_INET6	SOCK_DGRAM	IPPROTO_UDP	Failure, as socket is not connected.
PF_INET6	SOCK_STREAM	IPPROTO_SCTP	Send queued data and tear down association.
PF_INET6	SOCK_STREAM	IPPROTO_TCP	Send queued data, wait for ACK, then send FIN.

The shutdown function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The shutdown() system call fails if:

[EBADF]
	The s argument is not a valid file descriptor.
[EINVAL]
	The how argument is invalid.
[ENOTCONN]
	The s argument specifies a socket which is not connected.
[ENOTSOCK]
	The s argument does not refer to a socket.

The shutdown() system call is expected to comply with IEEE Std 1003.1g-2000 ("POSIX.1"), when finalized.

The shutdown() system call appeared in BSD 4.2 . The SHUT_RD, SHUT_WR, and SHUT_RDWR constants appeared in IEEE Std 1003.1g-2000 ("POSIX.1").

This manual page was updated by Bruce M. Simpson <Mt bms@FreeBSD.org> to reflect how shutdown() behaves with PF_INET and PF_INET6 sockets.

The ICMP "port unreachable" message should be generated in response to datagrams received on a local port to which s is bound after shutdown() is called.