shutdown(2)shutdown(2)NAMEshutdown() - shut down a socket
SYNOPSISDESCRIPTION
The system call is used to shut down a socket. In the case of a full-
duplex connection, can be used to either partially or fully shut down
the socket, depending upon the value of how.
how Interpretation
Further receives are disallowed
Further sends are disallowed
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 calls
return an end-of-file condition. A socket that has been shut down for
sending causes further calls to return an error and send the signal.
After a socket has been fully shut down, operations other than and
return appropriate errors, and the only other thing that can be done to
the socket is a
Multiple shutdowns on a connected socket and shutdowns on a socket that
is not connected may not return errors.
A on a connectionless socket, such as only marks the socket as unable
to do further or 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 sockets, if how is or the connection
begins to be closed gracefully in addition to the normal actions. How‐
ever, the call does not wait for the completion of the graceful discon‐
nection. The disconnection is complete when both sides of the connec‐
tion have done a with how equal to or Once the connection has been com‐
pletely terminated, the socket becomes fully shut down. The option
(see socket(2)) does not have any meaning for the call, but does for
the call. For more information on how the call interacts with sockets,
see socket(2).
If a is performed on a socket that has a pending on it, that socket
becomes fully shut down when how
AF_CCITT only
The how parameter behaves differently if the socket is of the address
family. If how is set to 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 or with how set to or
If how is set to or 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 call can still be read.
SCTP Only:
SCTP differs from TCP in that SCTP does not have half closed semantics.
Hence the call for SCTP is an approximation of the TCP 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 You can achieve the same results as half closed seman‐
tics in SCTP by using SCTP streams.
These are the possible SCTP operations:
Disables further receive operations.
No SCTP protocol action is taken.
Disables further send operations and initiates the SCTP shutdown
sequence.
Disables further send and receive operations and initiates the
SCTP shutdown sequence.
The major difference between SCTP and TCP is that SCTP initiates imme‐
diate and full protocol shutdown, whereas TCP causes TCP to go into the
half closed state. behaves the same for SCTP as TCP. The purpose of
SCTP is to close the SCTP association while still leaving the socket
descriptor open, so that the caller can receive back any data SCTP was
unable to deliver.
Note: SCTP is only available when the SCTP optional bundle is
installed.
X/Open Sockets Compilation Environment
See xopen_networking(7).
RETURN VALUE
Upon successful completion, returns 0; otherwise it returns −1 and is
set to indicate the error.
ERRORS
fails if any of the following conditions are encountered:
s is not a valid file descriptor.
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 or call, or set as a system parameter.
s is a valid file descriptor, but it is not a
socket.
The specified socket is not connected.
The specified socket is not connected.
The how argument is invalid.
WARNINGS
Linking binary objects compiled to specification and binary objects
compiled to specification to the same executable may result in unex‐
pected behavior, including application abnormal termination and unex‐
pected socket errors. See xopen_networking(7) for details and remedy.
FUTURE DIRECTION
Currently, the default behavior is the however, it might be changed to
in a future release. At that time, any behavior that is incompatible
with might be obsoleted. Applications that conform to the X/Open spec‐
ification now will avoid migration problems (see xopen_networking(7)).
AUTHOR
was developed by HP and the University of California, Berkeley.
SEE ALSOclose(2), connect(2), socket(2), sctp(7), xopen_networking(7).
STANDARDS CONFORMANCEshutdown(2)
