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XS_SETSOCKOPT(3)	     Crossroads	I/O Manual	      XS_SETSOCKOPT(3)

NAME
       xs_setsockopt - set Crossroads socket options

SYNOPSIS
       int xs_setsockopt (void *socket,	int option_name, const void
       *option_value, size_t option_len);

       Caution:	All options, with the exception	of XS_SUBSCRIBE,
       XS_UNSUBSCRIBE and XS_LINGER, only take effect for subsequent socket
       bind/connects.

DESCRIPTION
       The xs_setsockopt() function shall set the option specified by the
       option_name argument to the value pointed to by the option_value
       argument	for the	Crossroads socket pointed to by	the socket argument.
       The option_len argument is the size of the option value in bytes.

       The following socket options can	be set with the	xs_setsockopt()
       function:

   XS_SNDHWM: Set high water mark for outbound messages
       The XS_SNDHWM option shall set the high water mark for outbound
       messages	on the specified socket. The high water	mark is	a hard limit
       on the maximum number of	outstanding messages the library shall queue
       in memory for any single	peer that the specified	socket is
       communicating with.

       If this limit has been reached the socket shall enter an	exceptional
       state and depending on the socket type, the library shall take
       appropriate action such as blocking or dropping sent messages. Refer to
       the individual socket descriptions in xs_socket(3) for details on the
       exact action taken for each socket type.

       Option value type	 int

       Option value unit	 messages

       Default value		 1000

       Applicable socket types	 all

   XS_RCVHWM: Set high water mark for inbound messages
       The XS_RCVHWM option shall set the high water mark for inbound messages
       on the specified	socket.	The high water mark is a hard limit on the
       maximum number of outstanding messages the libray shall queue in	memory
       for any single peer that	the specified socket is	communicating with.

       If this limit has been reached the socket shall enter an	exceptional
       state and depending on the socket type, the library shall take
       appropriate action such as blocking or dropping sent messages. Refer to
       the individual socket descriptions in xs_socket(3) for details on the
       exact action taken for each socket type.

       Option value type	 int

       Option value unit	 messages

       Default value		 1000

       Applicable socket types	 all

   XS_AFFINITY:	Set I/O	thread affinity
       The XS_AFFINITY option shall set	the I/O	thread affinity	for newly
       created connections on the specified socket.

       Affinity	determines which threads from the Crossroads I/O thread	pool
       associated with the socket's context shall handle newly created
       connections. A value of zero specifies no affinity, meaning that	work
       shall be	distributed fairly among all Crossroads	I/O threads in the
       thread pool. For	non-zero values, the lowest bit	corresponds to thread
       1, second lowest	bit to thread 2	and so on. For example,	a value	of 3
       specifies that subsequent connections on	socket shall be	handled
       exclusively by I/O threads 1 and	2.

       See also	xs_init(3) for details on allocating the number	of I/O threads
       for a specific context.

       Option value type	 uint64_t

       Option value unit	 N/A (bitmap)

       Default value		 0

       Applicable socket types	 N/A

   XS_SUBSCRIBE: Establish message filter
       The XS_SUBSCRIBE	option shall establish a new message filter on a
       XS_SUB socket. Newly created XS_SUB sockets shall filter	out all
       incoming	messages, therefore you	should call this option	to establish
       an initial message filter.

       An empty	option_value of	length zero shall subscribe to all incoming
       messages. A non-empty option_value shall	subscribe to all messages
       beginning with the specified prefix. Multiple filters may be attached
       to a single XS_SUB socket, in which case	a message shall	be accepted if
       it matches at least one filter.

       Option value type	 binary	data

       Option value unit	 N/A

       Default value		 N/A

       Applicable socket types	 XS_SUB

   XS_UNSUBSCRIBE: Remove message filter
       The XS_UNSUBSCRIBE option shall remove an existing message filter on a
       XS_SUB socket. The filter specified must	match an existing filter
       previously established with the XS_SUBSCRIBE option. If the socket has
       several instances of the	same filter attached the XS_UNSUBSCRIBE	option
       shall remove only one instance, leaving the rest	in place and
       functional.

       Option value type	 binary	data

       Option value unit	 N/A

       Default value		 N/A

       Applicable socket types	 XS_SUB

   XS_IDENTITY:	Set socket identity
       The XS_IDENTITY option shall set	the identity of	the specified socket.
       Socket identity is used only by request/reply pattern. Namely, it can
       be used in tandem with a	XS_XREP	socket to route	messages to the	peer
       with specific identity.

       Identity	should be at least one byte and	at most	255 bytes long.
       Identities starting with	binary zero are	reserved for use by Crossroads
       infrastructure.

       Option value type	 binary	data

       Option value unit	 N/A

       Default value		 NULL

       Applicable socket types	 all

   XS_RATE: Set	multicast data rate
       The XS_RATE option shall	set the	maximum	send or	receive	data rate for
       multicast transports such as xs_pgm(7) using the	specified socket.

       Option value type	 int

       Option value unit	 kilobits per second

       Default value		 100

       Applicable socket types	 all, when using multicast
				 transports

   XS_RECOVERY_IVL: Set	multicast recovery interval
       The XS_RECOVERY_IVL option shall	set the	recovery interval for
       multicast transports using the specified	socket.	The recovery interval
       determines the maximum time in milliseconds that	a receiver can be
       absent from a multicast group before unrecoverable data loss will
       occur.

	   Caution
	   Exercise care when setting large recovery intervals as the data
	   needed for recovery will be held in memory. For example, a 1	minute
	   recovery interval at	a data rate of 1Gbps requires a	7GB in-memory
	   buffer.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 10000

       Applicable socket types	 all, when using multicast
				 transports

   XS_SNDBUF: Set kernel transmit buffer size
       The XS_SNDBUF option shall set the underlying kernel transmit buffer
       size for	the socket to the specified size in bytes. A value of zero
       means leave the OS default unchanged. For details please	refer to your
       operating system	documentation for the SO_SNDBUF	socket option.

       Option value type	 int

       Option value unit	 bytes

       Default value		 0

       Applicable socket types	 all

   XS_RCVBUF: Set kernel receive buffer	size
       The XS_RCVBUF option shall set the underlying kernel receive buffer
       size for	the socket to the specified size in bytes. A value of zero
       means leave the OS default unchanged. For details refer to your
       operating system	documentation for the SO_RCVBUF	socket option.

       Option value type	 int

       Option value unit	 bytes

       Default value		 0

       Applicable socket types	 all

   XS_LINGER: Set linger period	for socket shutdown
       The XS_LINGER option shall set the linger period	for the	specified
       socket. The linger period determines how	long pending messages which
       have yet	to be sent to a	peer shall linger in memory after a socket is
       closed with xs_close(3),	and further affects the	termination of the
       socket's	context	with xs_term(3). The following outlines	the different
       behaviours:

       o   The default value of	-1 specifies an	infinite linger	period.
	   Pending messages shall not be discarded after a call	to xs_close();
	   attempting to terminate the socket's	context	with xs_term() shall
	   block until all pending messages have been sent to a	peer.

       o   The value of	0 specifies no linger period. Pending messages shall
	   be discarded	immediately when the socket is closed with xs_close().

       o   Positive values specify an upper bound for the linger period	in
	   milliseconds. Pending messages shall	not be discarded after a call
	   to xs_close(); attempting to	terminate the socket's context with
	   xs_term() shall block until either all pending messages have	been
	   sent	to a peer, or the linger period	expires, after which any
	   pending messages shall be discarded.

	   Option value	type	     int
	   Option value	unit	     milliseconds
	   Default value	     -1	(infinite)
	   Applicable socket types   all

   XS_RECONNECT_IVL: Set reconnection interval
       The XS_RECONNECT_IVL option shall set the initial reconnection interval
       for the specified socket. The reconnection interval is the period the
       library shall wait between attempts to reconnect	disconnected peers
       when using connection-oriented transports.

	   Note
	   The reconnection interval may be randomized by the library to
	   prevent reconnection	storms in topologies with a large number of
	   peers per socket.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 100

       Applicable socket types	 all, only for
				 connection-oriented
				 transports

   XS_RECONNECT_IVL_MAX: Set maximum reconnection interval
       The XS_RECONNECT_IVL_MAX	option shall set the maximum reconnection
       interval	for the	specified socket. This is the maximum period the
       library shall wait between attempts to reconnect. On each reconnect
       attempt,	the previous interval shall be doubled untill
       XS_RECONNECT_IVL_MAX is reached.	This allows for	exponential backoff
       strategy. Default value means no	exponential backoff is performed and
       reconnect interval calculations are only	based on XS_RECONNECT_IVL.

	   Note
	   Values less than XS_RECONNECT_IVL will be ignored.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 0 (only use
				 XS_RECONNECT_IVL)

       Applicable socket types	 all, only for
				 connection-oriented
				 transports

   XS_BACKLOG: Set maximum length of the queue of outstanding connections
       The XS_BACKLOG option shall set the maximum length of the queue of
       outstanding peer	connections for	the specified socket; this only
       applies to connection-oriented transports. For details refer to your
       operating system	documentation for the listen function.

       Option value type	 int

       Option value unit	 connections

       Default value		 100

       Applicable socket types	 all, only for
				 connection-oriented
				 transports.

   XS_MAXMSGSIZE: Maximum acceptable inbound message size
       Limits the size of the inbound message. If a peer sends a message
       larger than XS_MAXMSGSIZE it is disconnected.

       Option value type	 uint64_t

       Option value unit	 bytes

       Default value		 2^64-1

       Applicable socket types	 all

   XS_MULTICAST_HOPS: Maximum network hops for multicast packets
       Sets the	time-to-live field in every multicast packet sent from this
       socket. The default is 1	which means that the multicast packets don't
       leave the local network.

       Option value type	 int

       Option value unit	 network hops

       Default value		 1

       Applicable socket types	 all, when using multicast
				 transports

   XS_RCVTIMEO:	Maximum	time before a recv operation returns with EAGAIN
       Sets the	timeout	for receive operation on the socket. If	the value is
       0, xs_recv(3) will return immediately, with a EAGAIN error if there is
       no message to receive. If the value is -1, it will block	until a
       message is available. For all other values, it will wait	for a message
       for that	amount of time before returning	with an	EAGAIN error.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 -1 (infinite)

       Applicable socket types	 all

   XS_SNDTIMEO:	Maximum	time before a send operation returns with EAGAIN
       Sets the	timeout	for send operation on the socket. If the value is 0,
       xs_send(3) will return immediately, with	a EAGAIN error if the message
       cannot be sent. If the value is -1, it will block until the message is
       sent. For all other values, it will try to send the message for that
       amount of time before returning with an EAGAIN error.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 -1 (infinite)

       Applicable socket types	 all

   XS_IPV4ONLY:	Use IPv4-only sockets
       Sets the	underlying native socket type. A value of 1 will use IPv4
       sockets,	while the value	of 0 will use IPv6 sockets. An IPv6 socket
       lets applications connect to and	accept connections from	both IPv4 and
       IPv6 hosts.

       Option value type	 int

       Option value unit	 boolean

       Default value		 1 (true)

       Applicable socket types	 all, when using TCP
				 transport.

   XS_KEEPALIVE: Enable	transport keepalives
       When set	to 1, this option enables use of protocol keepalives on	the
       socket, if supported by the underlying transport	protocol.

       Option value type	 int

       Option value unit	 boolean

       Default value		 0 (false)

       Applicable socket types	 all, when using TCP
				 transport.

   XS_SURVEY_TIMEOUT: Sets the deadline	for the	survey
       Specifies how long to wait for responses	to the survey. After the
       interval	expires, any firther calls to xs_recv()	will return EAGAIN
       error. All the responses	received later on will be silently discarded.
       Value of	-1 means infinite.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 -1 (infinite)

       Applicable socket types	 XS_SURVEYOR

RETURN VALUE
       The xs_setsockopt() function shall return zero if successful. Otherwise
       it shall	return -1 and set errno	to one of the values defined below.

ERRORS
       EINVAL
	   The requested option	option_name is unknown,	or the requested
	   option_len or option_value is invalid.

       ETERM
	   The context associated with the specified socket was	terminated.

       ENOTSOCK
	   The provided	socket was invalid.

       EINTR
	   The operation was interrupted by delivery of	a signal.

EXAMPLE
       Subscribing to messages on a XS_SUB socket.

	   /* Subscribe	to all messages	*/
	   rc =	xs_setsockopt (socket, XS_SUBSCRIBE, "", 0);
	   assert (rc == 0);
	   /* Subscribe	to messages prefixed with "ANIMALS.CATS" */
	   rc =	xs_setsockopt (socket, XS_SUBSCRIBE, "ANIMALS.CATS", 12);

       Setting I/O thread affinity.

	   int64_t affinity;
	   /* Incoming connections on TCP port 5555 shall be handled by	I/O thread 1 */
	   affinity = 1;
	   rc =	xs_setsockopt (socket, XS_AFFINITY, &affinity, sizeof affinity);
	   assert (rc == 0);
	   rc =	xs_bind	(socket, "tcp://lo:5555");
	   assert (rc != -1);
	   /* Incoming connections on TCP port 5556 shall be handled by	I/O thread 2 */
	   affinity = 2;
	   rc =	xs_setsockopt (socket, XS_AFFINITY, &affinity, sizeof affinity);
	   assert (rc == 0);
	   rc =	xs_bind	(socket, "tcp://lo:5556");
	   assert (rc != -1);

SEE ALSO
       xs_getsockopt(3)	xs_socket(3) xs(7)

AUTHORS
       The Crossroads documentation was	written	by Martin Sustrik
       <sustrik@250bpm.com[1]> and Martin Lucina <martin@lucina.net[2]>.

NOTES
	1. sustrik@250bpm.com
	   mailto:sustrik@250bpm.com

	2. martin@lucina.net
	   mailto:martin@lucina.net

Crossroads I/O 1.2.0		  08/08/2020		      XS_SETSOCKOPT(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLE | SEE ALSO | AUTHORS | NOTES

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