Provided by: libzmq3-dev_4.0.4+dfsg-2ubuntu0.1_amd64 
NAME
zmq_setsockopt - set 0MQ socket options
SYNOPSIS
int zmq_setsockopt (void *socket, int option_name, const void *option_value, size_t
option_len);
Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE, ZMQ_LINGER,
ZMQ_ROUTER_MANDATORY, ZMQ_PROBE_ROUTER, ZMQ_XPUB_VERBOSE, ZMQ_REQ_CORRELATE, and
ZMQ_REQ_RELAXED, only take effect for subsequent socket bind/connects.
Specifically, security options take effect for subsequent bind/connect calls, and can be
changed at any time to affect subsequent binds and/or connects.
DESCRIPTION
The zmq_setsockopt() function shall set the option specified by the option_name argument
to the value pointed to by the option_value argument for the 0MQ 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 zmq_setsockopt() function:
ZMQ_SNDHWM: Set high water mark for outbound messages
The ZMQ_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
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.
Note
0MQ does not guarantee that the socket will accept as many as ZMQ_SNDHWM messages, and
the actual limit may be as much as 60-70% lower depending on the flow of messages on
the socket.
Option value type int
Option value unit messages
Default value 1000
Applicable socket types all
ZMQ_RCVHWM: Set high water mark for inbound messages
The ZMQ_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
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_AFFINITY: Set I/O thread affinity
The ZMQ_AFFINITY option shall set 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_SUBSCRIBE: Establish message filter
The ZMQ_SUBSCRIBE option shall establish a new message filter on a ZMQ_SUB socket. Newly
created ZMQ_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 ZMQ_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 ZMQ_SUB
ZMQ_UNSUBSCRIBE: Remove message filter
The ZMQ_UNSUBSCRIBE option shall remove an existing message filter on a ZMQ_SUB socket.
The filter specified must match an existing filter previously established with the
ZMQ_SUBSCRIBE option. If the socket has several instances of the same filter attached the
ZMQ_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 ZMQ_SUB
ZMQ_IDENTITY: Set socket identity
The ZMQ_IDENTITY option shall set the identity of the specified socket when connecting to
a ROUTER socket. The identity should be from 1 to 255 bytes long and MAY NOT start with
binary zero.
If two clients use the same identity when connecting to a ROUTER, the ROUTER socket shall
accept only the first such client and reject the others.
Option value type binary data
Option value unit N/A
Default value NULL
Applicable socket types ZMQ_REQ, ZMQ_REP, ZMQ_ROUTER,
ZMQ_DEALER.
ZMQ_RATE: Set multicast data rate
The ZMQ_RATE option shall set the maximum send or receive data rate for multicast
transports such as zmq_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
ZMQ_RECOVERY_IVL: Set multicast recovery interval
The ZMQ_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
ZMQ_SNDBUF: Set kernel transmit buffer size
The ZMQ_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
ZMQ_RCVBUF: Set kernel receive buffer size
The ZMQ_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
ZMQ_LINGER: Set linger period for socket shutdown
The ZMQ_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 zmq_close(3), and further affects the
termination of the socket’s context with zmq_term(3). The following outlines the different
behaviours:
• 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_term() shall block until all pending messages have been sent to a
peer.
• The value of 0 specifies no linger period. Pending messages shall be discarded
immediately when the socket is closed with zmq_close().
• 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_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_RECONNECT_IVL: Set reconnection interval
The ZMQ_RECONNECT_IVL option shall set 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: Set maximum reconnection interval
The ZMQ_RECONNECT_IVL_MAX option shall set 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 transports
ZMQ_BACKLOG: Set maximum length of the queue of outstanding connections
The ZMQ_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.
ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
Limits the size of the inbound message. 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_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
ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN
Sets the timeout for receive 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_SNDTIMEO: Maximum time before a send operation returns with EAGAIN
Sets 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_IPV6: Enable IPv6 on socket
Set 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_IPV4ONLY: Use IPv4-only on socket
Set 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_IMMEDIATE: Queue messages only to completed connections
By default queues will fill on outgoing connections even if the connection has not
completed. This can lead to "lost" messages on sockets with round-robin routing (REQ,
PUSH, DEALER). If this option is set to 1, messages shall be queued only to completed
connections. 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, only for
connection-oriented transports.
ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER sockets
Sets the ROUTER socket behavior when an unroutable message is encountered. A value of 0 is
the default and discards the message silently when it cannot be routed. A value of 1
returns an EHOSTUNREACH error code if the message cannot be routed.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_ROUTER
ZMQ_ROUTER_RAW: switch ROUTER socket to raw mode
Sets the raw mode on the ROUTER, when set to 1. When the ROUTER socket is in raw mode, and
when using the tcp:// transport, it will read and write TCP data without 0MQ framing. This
lets 0MQ applications talk to non-0MQ applications. When using raw mode, you cannot set
explicit identities, and the ZMQ_MSGMORE flag is ignored when sending data messages. In
raw mode you can close a specific connection by sending it a zero-length message
(following the identity frame).
Note
This option is deprecated, please use ZMQ_STREAM sockets instead.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_ROUTER
ZMQ_PROBE_ROUTER: bootstrap connections to ROUTER sockets
When set to 1, the socket will automatically send an empty message when a new connection
is made or accepted. You may set this on REQ, DEALER, or ROUTER sockets connected to a
ROUTER socket. The application must filter such empty messages. The ZMQ_PROBE_ROUTER
option in effect provides the ROUTER application with an event signaling the arrival of a
new peer.
Note
do not set this option on a socket that talks to any other socket types: the results
are undefined.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_ROUTER, ZMQ_DEALER, ZMQ_REQ
ZMQ_XPUB_VERBOSE: provide all subscription messages on XPUB sockets
Sets the XPUB socket behavior on new subscriptions and unsubscriptions. A value of 0 is
the default and passes only new subscription messages to upstream. A value of 1 passes all
subscription messages upstream.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_XPUB
ZMQ_REQ_CORRELATE: match replies with requests
The default behavior of REQ sockets is to rely on the ordering of messages to match
requests and responses and that is usually sufficient. When this option is set to 1, the
REQ socket will prefix outgoing messages with an extra frame containing a request id. That
means the full message is (request id, 0, user frames...). The REQ socket will discard all
incoming messages that don’t begin with these two frames.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_REQ
ZMQ_REQ_RELAXED: relax strict alternation between request and reply
By default, a REQ socket does not allow initiating a new request with zmq_send(3) until
the reply to the previous one has been received. When set to 1, sending another message is
allowed and has the effect of disconnecting the underlying connection to the peer from
which the reply was expected, triggering a reconnection attempt on transports that support
it. The request-reply state machine is reset and a new request is sent to the next
available peer.
If set to 1, also enable ZMQ_REQ_CORRELATE to ensure correct matching of requests and
replies. Otherwise a late reply to an aborted request can be reported as the reply to the
superseding request.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types ZMQ_REQ
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_IDLE: Override TCP_KEEPCNT (or TCP_KEEPALIVE on some OS)
Override TCP_KEEPCNT(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_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_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_ACCEPT_FILTER: Assign filters to allow new TCP connections
Assign an arbitrary number of filters that will be applied for each new TCP transport
connection on a listening socket. If no filters are applied, then the TCP transport allows
connections from any IP address. If at least one filter is applied then new connection
source ip should be matched. To clear all filters call zmq_setsockopt(socket,
ZMQ_TCP_ACCEPT_FILTER, NULL, 0). Filter is a null-terminated string with ipv6 or ipv4
CIDR.
Option value type binary data
Option value unit N/A
Default value no filters (allow from all)
Applicable socket types all listening sockets, when
using TCP transports.
ZMQ_PLAIN_SERVER: Set PLAIN server role
Defines whether the socket will act as server for PLAIN security, see zmq_plain(7). A
value of 1 means the socket will act as PLAIN server. A value of 0 means the socket will
not act as PLAIN server, and its security role then depends on other option settings.
Setting this to 0 shall reset the socket security to NULL.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types all, when using TCP transport
ZMQ_PLAIN_USERNAME: Set PLAIN security username
Sets the username for outgoing connections over TCP or IPC. If you set this to a non-null
value, the security mechanism used for connections shall be PLAIN, see zmq_plain(7). If
you set this to a null value, the security mechanism used for connections shall be NULL,
see zmq_null(3).
Option value type character string
Option value unit N/A
Default value not set
Applicable socket types all, when using TCP transport
ZMQ_PLAIN_PASSWORD: Set PLAIN security password
Sets the password for outgoing connections over TCP or IPC. If you set this to a non-null
value, the security mechanism used for connections shall be PLAIN, see zmq_plain(7). If
you set this to a null value, the security mechanism used for connections shall be NULL,
see zmq_null(3).
Option value type character string
Option value unit N/A
Default value not set
Applicable socket types all, when using TCP transport
ZMQ_CURVE_SERVER: Set CURVE server role
Defines whether the socket will act as server for CURVE security, see zmq_curve(7). A
value of 1 means the socket will act as CURVE server. A value of 0 means the socket will
not act as CURVE server, and its security role then depends on other option settings.
Setting this to 0 shall reset the socket security to NULL. When you set this you must also
set the server’s secret key using the ZMQ_CURVE_SECRETKEY option. A server socket does not
need to know its own public key.
Option value type int
Option value unit 0, 1
Default value 0
Applicable socket types all, when using TCP transport
ZMQ_CURVE_PUBLICKEY: Set CURVE public key
Sets the socket’s long term public key. You must set this on CURVE client sockets, see
zmq_curve(7). You can provide the key as 32 binary bytes, or as a 40-character string
encoded in the Z85 encoding format. The public key must always be used with the matching
secret key. To generate a public/secret key pair, use zmq_curve_keypair(3).
Option value type binary data or Z85 text string
Option value size 32 or 40
Default value NULL
Applicable socket types all, when using TCP transport
ZMQ_CURVE_SECRETKEY: Set CURVE secret key
Sets the socket’s long term secret key. You must set this on both CURVE client and server
sockets, see zmq_curve(7). You can provide the key as 32 binary bytes, or as a
40-character string encoded in the Z85 encoding format. To generate a public/secret key
pair, use zmq_curve_keypair(3).
Option value type binary data or Z85 text string
Option value size 32 or 40
Default value NULL
Applicable socket types all, when using TCP transport
ZMQ_CURVE_SERVERKEY: Set CURVE server key
Sets the socket’s long term server key. You must set this on CURVE client sockets, see
zmq_curve(7). You can provide the key as 32 binary bytes, or as a 40-character string
encoded in the Z85 encoding format. This key must have been generated together with the
server’s secret key.
Option value type binary data or Z85 text string
Option value size 32 or 40
Default value NULL
Applicable socket types all, when using TCP transport
ZMQ_ZAP_DOMAIN: Set RFC 27 authentication domain
Sets the domain for ZAP (ZMQ RFC 27) authentication. For NULL security (the default on all
tcp:// connections), ZAP authentication only happens if you set a non-empty domain. For
PLAIN and CURVE security, ZAP requests are always made, if there is a ZAP handler present.
See http://rfc.zeromq.org/spec:27 for more details.
Option value type character string
Option value unit N/A
Default value not set
Applicable socket types all, when using TCP transport
ZMQ_CONFLATE: Keep only last message
If set, a socket shall keep only one message in its inbound/outbound queue, this message
being the last message received/the last message to be sent. Ignores ZMQ_RECVHWM and
ZMQ_SENDHWM options. Does not supports multi-part messages, in particular, only one part
of it is kept in the socket internal queue.
Option value type int
Option value unit boolean
Default value 0 (false)
Applicable socket types ZMQ_PULL, ZMQ_PUSH, ZMQ_SUB,
ZMQ_PUB, ZMQ_DEALER
RETURN VALUE
The zmq_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 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
Subscribing to messages on a ZMQ_SUB socket.
/* Subscribe to all messages */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "", 0);
assert (rc == 0);
/* Subscribe to messages prefixed with "ANIMALS.CATS" */
rc = zmq_setsockopt (socket, ZMQ_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 = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof (affinity));
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5555");
assert (rc);
/* Incoming connections on TCP port 5556 shall be handled by I/O thread 2 */
affinity = 2;
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof (affinity));
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5556");
assert (rc);
SEE ALSO
zmq_getsockopt(3) zmq_socket(3) zmq_plain(7) zmq_curve(7) zmq(7)
AUTHORS
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