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ZMQ_GETSOCKOPT(3)		  0MQ Manual		     ZMQ_GETSOCKOPT(3)

NAME
       zmq_getsockopt -	get 0MQ	socket options

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

DESCRIPTION
       The zmq_getsockopt() function shall retrieve the	value for the option
       specified by the	option_name argument for the 0MQ socket	pointed	to by
       the socket argument, and	store it in the	buffer pointed to by the
       option_value argument. The option_len argument is the size in bytes of
       the buffer pointed to by	option_value; upon successful completion
       zmq_getsockopt()	shall modify the option_len argument to	indicate the
       actual size of the option value stored in the buffer.

       The following options can be retrieved with the zmq_getsockopt()
       function:

   ZMQ_AFFINITY: Retrieve I/O thread affinity
       The ZMQ_AFFINITY	option shall retrieve the I/O thread affinity for
       newly created connections on the	specified socket.

       Affinity	determines which threads from the 0MQ 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 0MQ 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	zmq_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

   ZMQ_BACKLOG:	Retrieve maximum length	of the queue of	outstanding
       connections
       The ZMQ_BACKLOG option shall retrieve 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

   ZMQ_BINDTODEVICE: Retrieve name of device the socket	is bound to
       The ZMQ_BINDTODEVICE option retrieves the name of the device this
       socket is bound to, eg. an interface or VRF. If a socket	is bound to an
       interface, only packets received	from that interface are	processed by
       the socket. If device is	a VRF device, then subsequent binds/connects
       to that socket use addresses in the VRF routing table.

       Option value type	 character string

       Option value unit	 N/A

       Default value		 not set

       Applicable socket types	 all, when using TCP or	UDP
				 transports.

   ZMQ_CONNECT_TIMEOUT:	Retrieve connect() timeout
       Retrieves how long to wait before timing-out a connect()	system call.
       The connect() system call normally takes	a long time before it returns
       a time out error. Setting this option allows the	library	to time	out
       the call	at an earlier interval.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 0 (disabled)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_CURVE_PUBLICKEY:	Retrieve current CURVE public key
       Retrieves the current long term public key for the socket. You can
       provide either a	32 byte	buffer,	to retrieve the	binary key value, or a
       41 byte buffer, to retrieve the key in a	printable Z85 format. NOTE: to
       fetch a printable key, the buffer must be 41 bytes large	to hold	the
       40-char key value and one null byte.

       Option value type	 binary	data or	Z85 text
				 string

       Option value size	 32 or 41

       Default value		 null

       Applicable socket types	 all, when using TCP
				 transport

   ZMQ_CURVE_SECRETKEY:	Retrieve current CURVE secret key
       Retrieves the current long term secret key for the socket. You can
       provide either a	32 byte	buffer,	to retrieve the	binary key value, or a
       41 byte buffer, to retrieve the key in a	printable Z85 format. NOTE: to
       fetch a printable key, the buffer must be 41 bytes large	to hold	the
       40-char key value and one null byte.

       Option value type	 binary	data or	Z85 text
				 string

       Option value size	 32 or 41

       Default value		 null

       Applicable socket types	 all, when using TCP
				 transport

   ZMQ_CURVE_SERVERKEY:	Retrieve current CURVE server key
       Retrieves the current server key	for the	client socket. You can provide
       either a	32 byte	buffer,	to retrieve the	binary key value, or a 41-byte
       buffer, to retrieve the key in a	printable Z85 format. NOTE: to fetch a
       printable key, the buffer must be 41 bytes large	to hold	the 40-char
       key value and one null byte.

       Option value type	 binary	data or	Z85 text
				 string

       Option value size	 32 or 41

       Default value		 null

       Applicable socket types	 all, when using TCP
				 transport

   ZMQ_EVENTS: Retrieve	socket event state
       The ZMQ_EVENTS option shall retrieve the	event state for	the specified
       socket. The returned value is a bit mask	constructed by OR'ing a
       combination of the following event flags:

       ZMQ_POLLIN
	   Indicates that at least one message may be received from the
	   specified socket without blocking.

       ZMQ_POLLOUT
	   Indicates that at least one message may be sent to the specified
	   socket without blocking.

       The combination of a file descriptor returned by	the ZMQ_FD option
       being ready for reading but no actual events returned by	a subsequent
       retrieval of the	ZMQ_EVENTS option is valid; applications should	simply
       ignore this case	and restart their polling operation/event loop.

       Option value type	 int

       Option value unit	 N/A (flags)

       Default value		 N/A

       Applicable socket types	 all

   ZMQ_FD: Retrieve file descriptor associated with the	socket
       The ZMQ_FD option shall retrieve	the file descriptor associated with
       the specified socket. The returned file descriptor can be used to
       integrate the socket into an existing event loop; the 0MQ library shall
       signal any pending events on the	socket in an edge-triggered fashion by
       making the file descriptor become ready for reading.

	   Note
	   The ability to read from the	returned file descriptor does not
	   necessarily indicate	that messages are available to be read from,
	   or can be written to, the underlying	socket;	applications must
	   retrieve the	actual event state with	a subsequent retrieval of the
	   ZMQ_EVENTS option.

	   Note
	   The returned	file descriptor	is also	used internally	by the
	   zmq_send and	zmq_recv functions. As the descriptor is edge
	   triggered, applications must	update the state of ZMQ_EVENTS after
	   each	invocation of zmq_send or zmq_recv.To be more explicit:	after
	   calling zmq_send the	socket may become readable (and	vice versa)
	   without triggering a	read event on the file descriptor.

	   Caution
	   The returned	file descriptor	is intended for	use with a poll	or
	   similar system call only. Applications must never attempt to	read
	   or write data to it directly, neither should	they try to close it.

       Option value type	 int on	POSIX systems,
				 SOCKET	on Windows

       Option value unit	 N/A

       Default value		 N/A

       Applicable socket types	 all

   ZMQ_GSSAPI_PLAINTEXT: Retrieve GSSAPI plaintext or encrypted	status
       Returns the ZMQ_GSSAPI_PLAINTEXT	option,	if any,	previously set on the
       socket. A value of 1 means that communications will be plaintext. A
       value of	0 means	communications will be encrypted.

       Option value type	 int

       Option value unit	 0, 1

       Default value		 0 (false)

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_GSSAPI_PRINCIPAL: Retrieve the name of the GSSAPI principal
       The ZMQ_GSSAPI_PRINCIPAL	option shall retrieve the principal name set
       for the GSSAPI security mechanism. The returned value shall be a
       NULL-terminated string and MAY be empty.	The returned size SHALL
       include the terminating null byte.

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 null string

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_GSSAPI_SERVER: Retrieve current GSSAPI server role
       Returns the ZMQ_GSSAPI_SERVER option, if	any, previously	set on the
       socket.

       Option value type	 int

       Option value unit	 0, 1

       Default value		 0 (false)

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_GSSAPI_SERVICE_PRINCIPAL: Retrieve the name of the GSSAPI service
       principal
       The ZMQ_GSSAPI_SERVICE_PRINCIPAL	option shall retrieve the principal
       name of the GSSAPI server to which a GSSAPI client socket intends to
       connect.	The returned value shall be a NULL-terminated string and MAY
       be empty. The returned size SHALL include the terminating null byte.

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 null string

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Retrieve nametype for	service
       principal
       Returns the ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE option, if any,
       previously set on the socket. A value of	ZMQ_GSSAPI_NT_HOSTBASED	(0)
       means the name specified	with ZMQ_GSSAPI_SERVICE_PRINCIPAL is
       interpreted as a	host based name. A value of ZMQ_GSSAPI_NT_USER_NAME
       (1) means it is interpreted as a	local user name. A value of
       ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2)	means it is interpreted	as an unparsed
       principal name string (valid only with the krb5 GSSAPI mechanism).

       Option value type	 int

       Option value unit	 0, 1, 2

       Default value		 0
				 (ZMQ_GSSAPI_NT_HOSTBASED)

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Retrieve nametype for	service	principal
       Returns the ZMQ_GSSAPI_PRINCIPAL_NAMETYPE option, if any, previously
       set on the socket. A value of ZMQ_GSSAPI_NT_HOSTBASED (0) means the
       name specified with ZMQ_GSSAPI_PRINCIPAL	is interpreted as a host based
       name. A value of	ZMQ_GSSAPI_NT_USER_NAME	(1) means it is	interpreted as
       a local user name. A value of ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2) means it
       is interpreted as an unparsed principal name string (valid only with
       the krb5	GSSAPI mechanism).

       Option value type	 int

       Option value unit	 0, 1, 2

       Default value		 0
				 (ZMQ_GSSAPI_NT_HOSTBASED)

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_HANDSHAKE_IVL: Retrieve maximum handshake interval
       The ZMQ_HANDSHAKE_IVL option shall retrieve the maximum handshake
       interval	for the	specified socket. Handshaking is the exchange of
       socket configuration information	(socket	type, routing id, security)
       that occurs when	a connection is	first opened, only for
       connection-oriented transports. If handshaking does not complete	within
       the configured time, the	connection shall be closed. The	value 0	means
       no handshake time limit.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 30000

       Applicable socket types	 all but ZMQ_STREAM, only
				 for connection-oriented
				 transports

   ZMQ_IDENTITY: Retrieve socket identity
       This option name	is now deprecated. Use ZMQ_ROUTING_ID instead.
       ZMQ_IDENTITY remains as an alias	for now.

   ZMQ_IMMEDIATE: Retrieve attach-on-connect value
       Retrieve	the state of the attach	on connect value. If set to 1, will
       delay the attachment of a pipe on connect until the underlying
       connection has completed. This will cause the socket to block if	there
       are no other connections, but will prevent queues from filling on pipes
       awaiting	connection.

       Option value type	 int

       Option value unit	 boolean

       Default value		 0 (false)

       Applicable socket types	 all, primarily	when using
				 TCP/IPC transports.

   ZMQ_INVERT_MATCHING:	Retrieve inverted filtering status
       Returns the value of the	ZMQ_INVERT_MATCHING option. A value of 1 means
       the socket uses inverted	prefix matching.

       On PUB and XPUB sockets,	this causes messages to	be sent	to all
       connected sockets except	those subscribed to a prefix that matches the
       message.	On SUB sockets,	this causes only incoming messages that	do not
       match any of the	socket's subscriptions to be received by the user.

       Whenever	ZMQ_INVERT_MATCHING is set to 1	on a PUB socket, all SUB
       sockets connecting to it	must also have the option set to 1. Failure to
       do so will have the SUB sockets reject everything the PUB socket	sends
       them. XSUB sockets do not need to do this because they do not filter
       incoming	messages.

       Option value type	 int

       Option value unit	 0,1

       Default value		 0

       Applicable socket types	 ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB

   ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status
       Retrieve	the IPv4-only option for the socket. This option is
       deprecated. Please use the ZMQ_IPV6 option.

       Option value type	 int

       Option value unit	 boolean

       Default value		 1 (true)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_IPV6: Retrieve IPv6 socket status
       Retrieve	the IPv6 option	for the	socket.	A value	of 1 means IPv6	is
       enabled on the socket, while 0 means the	socket will use	only IPv4.
       When IPv6 is enabled the	socket will connect to,	or accept connections
       from, both IPv4 and IPv6	hosts.

       Option value type	 int

       Option value unit	 boolean

       Default value		 0 (false)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_LAST_ENDPOINT: Retrieve the last	endpoint set
       The ZMQ_LAST_ENDPOINT option shall retrieve the last endpoint bound for
       TCP and IPC transports. The returned value will be a string in the form
       of a ZMQ	DSN. Note that if the TCP host is INADDR_ANY, indicated	by a
       *, then the returned address will be 0.0.0.0 (for IPv4).

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 NULL

       Applicable socket types	 all, when binding TCP or
				 IPC transports

   ZMQ_LINGER: Retrieve	linger period for socket shutdown
       The ZMQ_LINGER option shall retrieve 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 zmq_close(3), and further affects the
       termination of the socket's context with	zmq_ctx_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
	   zmq_close();	attempting to terminate	the socket's context with
	   zmq_ctx_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
	   zmq_close().

       o   Positive values specify an upper bound for the linger period	in
	   milliseconds. Pending messages shall	not be discarded after a call
	   to zmq_close(); attempting to terminate the socket's	context	with
	   zmq_ctx_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

   ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
       The option shall	retrieve limit for the inbound messages. If a peer
       sends a message larger than ZMQ_MAXMSGSIZE it is	disconnected. Value of
       -1 means	no limit.

       Option value type	 int64_t

       Option value unit	 bytes

       Default value		 -1

       Applicable socket types	 all

   ZMQ_MECHANISM: Retrieve current security mechanism
       The ZMQ_MECHANISM option	shall retrieve the current security mechanism
       for the socket.

       Option value type	 int

       Option value unit	 ZMQ_NULL, ZMQ_PLAIN,
				 ZMQ_CURVE, or ZMQ_GSSAPI

       Default value		 ZMQ_NULL

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_MULTICAST_HOPS: Maximum network hops for	multicast packets
       The option shall	retrieve time-to-live used for outbound	multicast
       packets.	The default of 1 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

   ZMQ_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast
       packets
       The ZMQ_MULTICAST_MAXTPDU option	shall retrieve the maximum transport
       data unit size used for outbound	multicast packets.

       This must be set	at or below the	minimum	Maximum	Transmission Unit
       (MTU) for all network paths over	which multicast	reception is required.

       Option value type	 int

       Option value unit	 bytes

       Default value		 1500

       Applicable socket types	 all, when using multicast
				 transports

   ZMQ_PLAIN_PASSWORD: Retrieve	current	password
       The ZMQ_PLAIN_PASSWORD option shall retrieve the	last password set for
       the PLAIN security mechanism. The returned value	shall be a
       NULL-terminated string and MAY be empty.	The returned size SHALL
       include the terminating null byte.

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 null string

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_PLAIN_SERVER: Retrieve current PLAIN server role
       Returns the ZMQ_PLAIN_SERVER option, if any, previously set on the
       socket.

       Option value type	 int

       Option value unit	 0, 1

       Default value		 int

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_PLAIN_USERNAME: Retrieve	current	PLAIN username
       The ZMQ_PLAIN_USERNAME option shall retrieve the	last username set for
       the PLAIN security mechanism. The returned value	shall be a
       NULL-terminated string and MAY be empty.	The returned size SHALL
       include the terminating null byte.

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 null string

       Applicable socket types	 all, when using TCP or	IPC
				 transports

   ZMQ_USE_FD: Retrieve	the pre-allocated socket file descriptor
       The ZMQ_USE_FD option shall retrieve the	pre-allocated file descriptor
       that has	been assigned to a ZMQ socket, if any. -1 shall	be returned if
       a pre-allocated file descriptor was not set for the socket.

       Option value type	 int

       Option value unit	 file descriptor

       Default value		 -1

       Applicable socket types	 all bound sockets, when
				 using IPC or TCP transport

   ZMQ_RATE: Retrieve multicast	data rate
       The ZMQ_RATE option shall retrieve the maximum send or receive data
       rate for	multicast transports 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

   ZMQ_RCVBUF: Retrieve	kernel receive buffer size
       The ZMQ_RCVBUF option shall retrieve the	underlying kernel receive
       buffer size for the specified socket. For details refer to your
       operating system	documentation for the SO_RCVBUF	socket option.

       Option value type	 int

       Option value unit	 bytes

       Default value		 8192

       Applicable socket types	 all

   ZMQ_RCVHWM: Retrieve	high water mark	for inbound messages
       The ZMQ_RCVHWM option shall return 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 0MQ shall queue in	memory
       for any single peer that	the specified socket is	communicating with. A
       value of	zero means no limit.

       If this limit has been reached the socket shall enter an	exceptional
       state and depending on the socket type, 0MQ shall take appropriate
       action such as blocking or dropping sent	messages. Refer	to the
       individual socket descriptions in zmq_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

   ZMQ_RCVMORE:	More message data parts	to follow
       The ZMQ_RCVMORE option shall return True	(1) if the message part	last
       received	from the socket	was a data part	with more parts	to follow. If
       there are no data parts to follow, this option shall return False (0).

       Refer to	zmq_send(3) and	zmq_recv(3) for	a detailed description of
       multi-part messages.

       Option value type	 int

       Option value unit	 boolean

       Default value		 N/A

       Applicable socket types	 all

   ZMQ_RCVTIMEO: Maximum time before a socket operation	returns	with EAGAIN
       Retrieve	the timeout for	recv operation on the socket. If the value is
       0, zmq_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

   ZMQ_RECONNECT_IVL: Retrieve reconnection interval
       The ZMQ_RECONNECT_IVL option shall retrieve the initial reconnection
       interval	for the	specified socket. The reconnection interval is the
       period 0MQ shall	wait between attempts to reconnect disconnected	peers
       when using connection-oriented transports. The value -1 means no
       reconnection.

	   Note
	   The reconnection interval may be randomized by 0MQ 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

   ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection	interval
       The ZMQ_RECONNECT_IVL_MAX option	shall retrieve the maximum
       reconnection interval for the specified socket. This is the maximum
       period 0MQ shall	wait between attempts to reconnect. On each reconnect
       attempt,	the previous interval shall be doubled untill
       ZMQ_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 ZMQ_RECONNECT_IVL.

	   Note
	   Values less than ZMQ_RECONNECT_IVL will be ignored.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 0 (only use
				 ZMQ_RECONNECT_IVL)

       Applicable socket types	 all, only for
				 connection-oriented
				 transport

   ZMQ_RECOVERY_IVL: Get multicast recovery interval
       The ZMQ_RECOVERY_IVL option shall retrieve 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.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 10000

       Applicable socket types	 all, when using multicast
				 transports

   ZMQ_ROUTING_ID: Retrieve socket routing id
       The ZMQ_ROUTING_ID option shall retrieve	the routing id of the
       specified socket. Routing ids are used only by the request/reply
       pattern.	Specifically, it can be	used in	tandem with ROUTER socket to
       route messages to the peer with a specific routing id.

       A routing id must be at least one byte and at most 255 bytes long.
       Identities starting with	a zero byte are	reserved for use by the	0MQ
       infrastructure.

       Option value type	 binary	data

       Option value unit	 N/A

       Default value		 NULL

       Applicable socket types	 ZMQ_REP, ZMQ_REQ,
				 ZMQ_ROUTER, ZMQ_DEALER.

   ZMQ_SNDBUF: Retrieve	kernel transmit	buffer size
       The ZMQ_SNDBUF option shall retrieve the	underlying kernel transmit
       buffer size for the specified socket. For details refer to your
       operating system	documentation for the SO_SNDBUF	socket option.

       Option value type	 int

       Option value unit	 bytes

       Default value		 8192

       Applicable socket types	 all

   ZMQ_SNDHWM: Retrieves high water mark for outbound messages
       The ZMQ_SNDHWM option shall return 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 0MQ shall queue in	memory
       for any single peer that	the specified socket is	communicating with. A
       value of	zero means no limit.

       If this limit has been reached the socket shall enter an	exceptional
       state and depending on the socket type, 0MQ shall take appropriate
       action such as blocking or dropping sent	messages. Refer	to the
       individual socket descriptions in zmq_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

   ZMQ_SNDTIMEO: Maximum time before a socket operation	returns	with EAGAIN
       Retrieve	the timeout for	send operation on the socket. If the value is
       0, zmq_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

   ZMQ_SOCKS_PROXY: Retrieve SOCKS5 proxy address
       The ZMQ_SOCKS_PROXY option shall	retrieve the SOCKS5 proxy address in
       string format. The returned value shall be a NULL-terminated string and
       MAY be empty. The returned size SHALL include the terminating null
       byte.

       Option value type	 NULL-terminated character
				 string

       Option value unit	 N/A

       Default value		 null string

       Applicable socket types	 all, when using TCP
				 transports

   ZMQ_TCP_KEEPALIVE: Override SO_KEEPALIVE socket option
       Override	SO_KEEPALIVE socket option(where supported by OS). The default
       value of	-1 means to skip any overrides and leave it to OS default.

       Option value type	 int

       Option value unit	 -1,0,1

       Default value		 -1 (leave to OS default)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket option
       Override	TCP_KEEPCNT socket option(where	supported by OS). The default
       value of	-1 means to skip any overrides and leave it to OS default.

       Option value type	 int

       Option value unit	 -1,>0

       Default value		 -1 (leave to OS default)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
       Override	TCP_KEEPIDLE(or	TCP_KEEPALIVE on some OS) socket option	(where
       supported by OS). The default value of -1 means to skip any overrides
       and leave it to OS default.

       Option value type	 int

       Option value unit	 -1,>0

       Default value		 -1 (leave to OS default)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option
       Override	TCP_KEEPINTVL socket option(where supported by OS). The
       default value of	-1 means to skip any overrides and leave it to OS
       default.

       Option value type	 int

       Option value unit	 -1,>0

       Default value		 -1 (leave to OS default)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_TCP_MAXRT: Retrieve Max TCP Retransmit Timeout
       On OSes where it	is supported, retrieves	how long before	an
       unacknowledged TCP retransmit times out.	The system normally attempts
       many TCP	retransmits following an exponential backoff strategy. This
       means that after	a network outage, it may take a	long time before the
       session can be re-established. Setting this option allows the timeout
       to happen at a shorter interval.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 0 (leave to OS	default)

       Applicable socket types	 all, when using TCP
				 transports.

   ZMQ_THREAD_SAFE: Retrieve socket thread safety
       The ZMQ_THREAD_SAFE option shall	retrieve a boolean value indicating
       whether or not the socket is threadsafe.	Currently ZMQ_CLIENT and
       ZMQ_SERVER sockets are threadsafe.

       Option value type	 boolean

       Applicable socket types	 all

   ZMQ_TOS: Retrieve the Type-of-Service socket	override status
       Retrieve	the IP_TOS option for the socket.

       Option value type	 int

       Option value unit	 >0

       Default value		 0

       Applicable socket types	 all, only for
				 connection-oriented
				 transports

   ZMQ_TYPE: Retrieve socket type
       The ZMQ_TYPE option shall retrieve the socket type for the specified
       socket. The socket type is specified at socket creation time and	cannot
       be modified afterwards.

       Option value type	 int

       Option value unit	 N/A

       Default value		 N/A

       Applicable socket types	 all

   ZMQ_ZAP_DOMAIN: Retrieve RFC	27 authentication domain
       The ZMQ_ZAP_DOMAIN option shall retrieve	the last ZAP domain set	for
       the socket. The returned	value shall be a NULL-terminated string	and
       MAY be empty. An	empty string means that	ZAP authentication is
       disabled. The returned size SHALL include the terminating null byte.

       Option value type	 character string

       Option value unit	 N/A

       Default value		 not set

       Applicable socket types	 all, when using TCP
				 transport

   ZMQ_ZAP_ENFORCE_DOMAIN: Retrieve ZAP	domain handling	mode
       The ZMQ_ZAP_ENFORCE_DOMAIN option shall retrieve	the flag that
       determines whether a ZAP	domain is strictly required or not.

       Option value type	 int

       Option value unit	 0, 1

       Default value		 0

       Applicable socket types	 all, when using ZAP

   ZMQ_VMCI_BUFFER_SIZE: Retrieve buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_SIZE	option shall retrieve the size of the
       underlying buffer for the socket. Used during negotiation before	the
       connection is established.

       Option value type	 uint64_t

       Option value unit	 bytes

       Default value		 65546

       Applicable socket types	 all, when using VMCI
				 transport

   ZMQ_VMCI_BUFFER_MIN_SIZE: Retrieve min buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_MIN_SIZE option shall retrieve the min size of the
       underlying buffer for the socket. Used during negotiation before	the
       connection is established.

       Option value type	 uint64_t

       Option value unit	 bytes

       Default value		 128

       Applicable socket types	 all, when using VMCI
				 transport

   ZMQ_VMCI_BUFFER_MAX_SIZE: Retrieve max buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_MAX_SIZE option shall retrieve the max size of the
       underlying buffer for the socket. Used during negotiation before	the
       connection is established.

       Option value type	 uint64_t

       Option value unit	 bytes

       Default value		 262144

       Applicable socket types	 all, when using VMCI
				 transport

   ZMQ_VMCI_CONNECT_TIMEOUT: Retrieve connection timeout of the	VMCI socket
       The ZMQ_VMCI_CONNECT_TIMEOUT option shall retrieve connection timeout
       for the socket.

       Option value type	 int

       Option value unit	 milliseconds

       Default value		 -1

       Applicable socket types	 all, when using VMCI
				 transport

   ZMQ_MULTICAST_LOOP: Retrieve	multicast local	loopback configuration
       Retrieve	the current multicast loopback configuration. A	value of 1
       means that the multicast	packets	sent on	this socket will be looped
       back to local listening interface.

       Option value type	 int

       Option value unit	 0, 1

       Default value		 1

       Applicable socket types	 ZMQ_RADIO, when using UDP
				 multicast transport

   ZMQ_ROUTER_NOTIFY: Retrieve router socket notification settings
       Retrieve	the current notification settings of a router socket. The
       returned	value is a bitmask composed of ZMQ_NOTIFY_CONNECT and
       ZMQ_NOTIFY_DISCONNECT flags, meaning connect and	disconnect
       notifications are enabled, respectively.	A value	of 0 means the
       notifications are off.

	   Note
	   in DRAFT state, not yet available in	stable releases.

       Option value type	 int

       Option value unit	 0, ZMQ_NOTIFY_CONNECT,
				 ZMQ_NOTIFY_DISCONNECT,
				 ZMQ_NOTIFY_CONNECT|ZMQ_NOTIFY_DISCONNECT

       Default value		 0

       Applicable socket types	 ZMQ_ROUTER

RETURN VALUE
       The zmq_getsockopt() 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, or the size of the buffer
	   pointed to by option_value, as specified by option_len, is
	   insufficient	for storing the	option value.

       ETERM
	   The 0MQ 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
       Retrieving the high water mark for outgoing messages.

	   /* Retrieve high water mark into sndhwm */
	   int sndhwm;
	   size_t sndhwm_size =	sizeof (sndhwm);
	   rc =	zmq_getsockopt (socket,	ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
	   assert (rc == 0);

SEE ALSO
       zmq_setsockopt(3) zmq_socket(3) zmq(7)

AUTHORS
       This page was written by	the 0MQ	community. To make a change please
       read the	0MQ Contribution Policy	at
       http://www.zeromq.org/docs:contributing.

0MQ 4.3.1			  01/12/2019		     ZMQ_GETSOCKOPT(3)

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

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