int setsockopt(

int socket,

int level,

int option_name,

const void *option_value,

int option_len

);

Type

Meaning

SO_BROADCAST

Permits sending of broadcast messages, if this is supported by the protocol. This option takes an int value. This is a Boolean option.

SO_REUSEADDR

Specifies that the rules used in validating addresses supplied to bind() should allow reuse of local addresses, if this is supported by the protocol. This option takes an int value. This is a Boolean option.

SO_KEEPALIVE

Keeps connections active by enabling the periodic transmission of messages, if this is supported by the protocol. This option takes an int value.

Type

Meaning

SO_LINGER

Lingers on a closesocket function if data is present. This option controls the action taken when unsent messages queue on a socket and closesocket is performed. If SO_LINGER is set, the system blocks the calling thread during closesocket until it can transmit the data or until the time expires. If SO_LINGER is not specified, and closesocket is issued, the system handles the call in a way that allows the calling thread to continue as quickly as possible. This option takes a linger structure, as defined in the socket.h header, to specify the state of the option and linger interval.

SO_OOBINLINE

Leaves received out-of-band data (data marked urgent) inline. This option takes an int value. This is a Boolean option.

SO_SNDBUF

Sets send buffer size. This option takes an int value.

SO_RCVBUF

Sets receive buffer size. This option takes an int value.

SO_DONTROUTE

Requests that outgoing messages bypass the standard routing facilities. The destination shall be on a directly-connected network, and messages are directed to the appropriate network interface according to the destination address. The effect, if any, of this option depends on what protocol is in use. This option takes an int value. This is a Boolean option.

SO_RCVLOWAT

Sets the minimum number of bytes to process for socket input operations. The default value for SO_RCVLOWAT is 1. If SO_RCVLOWAT is set to a larger value, blocking receive calls normally wait until they have received the smaller of the low water mark value or the requested amount. (They may return less than the low water mark if an error occurs, a signal is caught, or the type of data next in the receive queue is different from that returned; for example, out-of-band data.) This option takes an int value. Note that not all implementations allow this option to be set.

SO_RCVTIMEO

Sets the timeout value that specifies the maximum amount of time an input function waits until it completes. It accepts a timeval structure with the number of seconds and microseconds specifying the limit on how long to wait for an input operation to complete. If a receive operation has blocked for this much time without receiving additional data, it shall return with a partial count or errno set to [EAGAIN] or [EWOULDBLOCK] if no data is received. The default for this option is zero, which indicates that a receive operation shall not time out. This option takes a timeval structure.

SO_SNDLOWAT

Sets the minimum number of bytes to process for socket output operations. Non-blocking output operations shall process no data if flow control does not allow the smaller of the send low water mark value or the entire request to be processed. This option takes an int value. Note that not all implementations allow this option to be set.

SO_SNDTIMEO

Sets the timeout value specifying the amount of time that an output function blocks because flow control prevents data from being sent. If a send operation has blocked for this time, it shall return with a partial count or with errno set to [EAGAIN] or [EWOULDBLOCK] if no data is sent. The default for this option is zero, which indicates that a send operation shall not time out. This option stores a timeval structure.