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_HANDOVER, ZMQ_ROUTER_MANDATORY,
ZMQ_PROBE_ROUTER, ZMQ_XPUB_VERBOSE, ZMQ_XPUB_VERBOSER, ZMQ_REQ_CORRELATE,
ZMQ_REQ_RELAXED, ZMQ_SNDHWM and ZMQ_RCVHWM, 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. For
options taking a value of type "character string", the provided byte
data should either contain no zero bytes, or end in a single zero byte
(terminating ASCII NUL character).
The following socket options can be set with the
zmq_setsockopt() function:
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_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_BINDTODEVICE: Set name of device to bind the socket to¶
The ZMQ_BINDTODEVICE option binds this socket to a particular device, eg.
an interface or VRF. If a socket is bound to an interface, only packets
received from that particular 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.
Note
requires setting CAP_NET_RAW on the compiled program.
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_RID: Assign the next outbound connection id¶
This option name is now deprecated. Use ZMQ_CONNECT_ROUTING_ID instead.
ZMQ_CONNECT_RID remains as an alias for now.
ZMQ_CONNECT_ROUTING_ID: Assign the next outbound routing id¶
The ZMQ_CONNECT_ROUTING_ID option sets the peer id of the peer connected
via the next zmq_connect() call, such that that connection is immediately
ready for data transfer with the given routing id. This option applies only to
the first subsequent call to zmq_connect(), zmq_connect() calls thereafter use
the default connection behaviour.
Typical use is to set this socket option ahead of each
zmq_connect() call. Each connection MUST be assigned a unique routing id.
Assigning a routing id that is already in use is not allowed.
Useful when connecting ROUTER to ROUTER, or STREAM to STREAM, as
it allows for immediate sending to peers. Outbound routing id framing
requirements for ROUTER and STREAM sockets apply.
The routing id must be from 1 to 255 bytes long and MAY NOT start
with a zero byte (such routing ids are reserved for internal use by the 0MQ
infrastructure).
Option value type |
binary data |
Option value unit |
N/A |
Default value |
NULL |
Applicable socket types |
ZMQ_ROUTER, ZMQ_STREAM |
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_RCVHWM and ZMQ_SNDHWM options. Does not support multi-part
messages, in particular, only one part of it is kept in the socket internal
queue.
Note
If recv is not called on the inbound socket, the queue and memory
will grow with each message received. Use zmq_getsockopt(3) with
ZMQ_EVENTS to trigger the conflation of the messages.
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 |
ZMQ_CONNECT_TIMEOUT: Set connect() timeout¶
Sets 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: 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 and terminated
in a null byte. The public key must always be used with the matching secret
key. To generate a public/secret key pair, use zmq_curve_keypair(3). To
derive the public key from a secret key, use zmq_curve_public(3).
Note
an option value size of 40 is supported for backwards
compatibility, though is deprecated.
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: 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 and terminated in a null byte. To generate a public/secret key pair,
use zmq_curve_keypair(3). To derive the public key from a secret key,
use zmq_curve_public(3).
Note
an option value size of 40 is supported for backwards
compatibility, though is deprecated.
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_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_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 and terminated
in a null byte. This key must have been generated together with the
server’s secret key. To generate a public/secret key pair, use
zmq_curve_keypair(3).
Note
an option value size of 40 is supported for backwards
compatibility, though is deprecated.
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_GSSAPI_PLAINTEXT: Disable GSSAPI encryption¶
Defines whether communications on the socket will be encrypted, see
zmq_gssapi(7). 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 transport |
ZMQ_GSSAPI_PRINCIPAL: Set name of GSSAPI principal¶
Sets the name of the principal for whom GSSAPI credentials should be acquired.
Option value type |
character string |
Option value unit |
N/A |
Default value |
not set |
Applicable socket types |
all, when using TCP transport |
ZMQ_GSSAPI_SERVER: Set GSSAPI server role¶
Defines whether the socket will act as server for GSSAPI security, see
zmq_gssapi(7). A value of 1 means the socket will act as GSSAPI
server. A value of 0 means the socket will act as GSSAPI client.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 (false) |
Applicable socket types |
all, when using TCP transport |
ZMQ_GSSAPI_SERVICE_PRINCIPAL: Set name of GSSAPI service principal¶
Sets the name of the principal of the GSSAPI server to which a GSSAPI client
intends to connect.
Option value type |
character string |
Option value unit |
N/A |
Default value |
not set |
Applicable socket types |
all, when using TCP transport |
ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Set name type of service principal¶
Sets the name type of the GSSAPI service principal. 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 transport |
ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Set name type of principal¶
Sets the name type of the GSSAPI principal. 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 transport |
ZMQ_HANDSHAKE_IVL: Set maximum handshake interval¶
The ZMQ_HANDSHAKE_IVL option shall set 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_HEARTBEAT_IVL: Set interval between sending ZMTP heartbeats¶
The ZMQ_HEARTBEAT_IVL option shall set the interval between sending ZMTP
heartbeats for the specified socket. If this option is set and is
greater than 0, then a PING ZMTP command will be sent every
ZMQ_HEARTBEAT_IVL milliseconds.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
0 |
Applicable socket types |
all, when using connection-oriented
transports |
ZMQ_HEARTBEAT_TIMEOUT: Set timeout for ZMTP heartbeats¶
The ZMQ_HEARTBEAT_TIMEOUT option shall set how long to wait before
timing-out a connection after sending a PING ZMTP command and not
receiving any traffic. This option is only valid if ZMQ_HEARTBEAT_IVL
is also set, and is greater than 0. The connection will time out if there is
no traffic received after sending the PING command, but the received
traffic does not have to be a PONG command - any received traffic will
cancel the timeout.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
0 normally, ZMQ_HEARTBEAT_IVL if it is
set |
Applicable socket types |
all, when using connection-oriented
transports |
ZMQ_HEARTBEAT_TTL: Set the TTL value for ZMTP heartbeats¶
The ZMQ_HEARTBEAT_TTL option shall set the timeout on the remote peer for
ZMTP heartbeats. If this option is greater than 0, the remote side shall time
out the connection if it does not receive any more traffic within the TTL
period. This option does not have any effect if ZMQ_HEARTBEAT_IVL is
not set or is 0. Internally, this value is rounded down to the nearest
decisecond, any value less than 100 will have no effect.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
0 |
Maximum value |
6553599 (which is 2^16-1 deciseconds) |
Applicable socket types |
all, when using connection-oriented
transports |
ZMQ_IDENTITY: Set socket identity¶
This option name is now deprecated. Use ZMQ_ROUTING_ID instead. ZMQ_IDENTITY
remains as an alias for now.
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_INVERT_MATCHING: Invert message filtering¶
Reverses the filtering behavior of PUB-SUB sockets, when set to 1.
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_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_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
disconnected with zmq_disconnect(3) or 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:
•A value of -1 specifies an infinite linger
period. Pending messages shall not be discarded after a call to
zmq_disconnect() or 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.
•The value of 0 specifies no linger period.
Pending messages shall be discarded immediately after a call to
zmq_disconnect() or 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_disconnect() or
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¶
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 |
The ZMQ_METADATA option shall add application metadata to the specified
socket, the metadata is exchanged with peers during connection setup. A
metadata property is specfied as a string, delimited by a colon, starting with
the metadata property followed by the metadata value, for example
"X-key:value". Property names are restrited to maximum 255
characters and must be prefixed by "X-". Multiple application
metadata properties can be added to a socket by executing zmq_setsockopt()
multiple times. As the argument is a null-terminated string, binary data must
be encoded before it is added e.g. using Z85 (zmq_z85_encode(3)).
Note
in DRAFT state, not yet available in stable releases.
Option value type |
character string |
Option value unit |
N/A |
Default value |
not set |
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_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast packets¶
Sets 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: 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_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_USE_FD: Set the pre-allocated socket file descriptor¶
When set to a positive integer value before zmq_bind is called on the socket,
the socket shall use the corresponding file descriptor for connections over
TCP or IPC instead of allocating a new file descriptor. Useful for writing
systemd socket activated services. If set to -1 (default), a new file
descriptor will be allocated instead (default behaviour).
Note
if set after calling zmq_bind, this option shall have no effect.
NOTE: the file descriptor passed through MUST have been ran through the
"bind" and "listen" system calls beforehand. Also,
socket option that would normally be passed through zmq_setsockopt like TCP
buffers length, IP_TOS or SO_REUSEADDR MUST be set beforehand by the caller,
as they must be set before the socket is bound.
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_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_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_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 -1 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 |
-1 |
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.
Note
0MQ does not guarantee that the socket will be able to queue as
many as ZMQ_RCVHWM messages, and the actual limit may be lower or higher,
depending on socket transport. A notable example is for sockets using TCP
transport; see zmq_tcp(7).
Option value type |
int |
Option value unit |
messages |
Default value |
1000 |
Applicable socket types |
all |
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_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_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_REQ_CORRELATE: match replies with requests¶
The default behaviour 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 previous replies will be
discarded if any. 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_ROUTER_HANDOVER: handle duplicate client routing ids on ROUTER sockets¶
If two clients use the same routing id when connecting to a ROUTER, the results
shall depend on the ZMQ_ROUTER_HANDOVER option setting. If that is not set (or
set to the default of zero), the ROUTER socket shall reject clients trying to
connect with an already-used routing id. If that option is set to 1, the
ROUTER socket shall hand-over the connection to the new client and disconnect
the existing one.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
ZMQ_ROUTER |
ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER sockets¶
Sets the ROUTER socket behaviour when an unroutable message is encountered. A
value of 0 is the default and discards the message silently when it cannot be
routed or the peers SNDHWM is reached. A value of 1 returns an
EHOSTUNREACH error code if the message cannot be routed or
EAGAIN error code if the SNDHWM is reached and ZMQ_DONTWAIT was used.
Without ZMQ_DONTWAIT it will block until the SNDTIMEO is reached or a spot in
the send queue opens up.
When ZMQ_ROUTER_MANDATORY is set to 1, ZMQ_POLLOUT events
will be generated if one or more messages can be sent to at least one of the
peers. If ZMQ_ROUTER_MANDATORY is set to 0, the socket will generate a
ZMQ_POLLOUT event on every call to zmq_poll resp.
zmq_poller_wait_all.
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_SNDMORE
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 routing
id 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_ROUTING_ID: Set socket routing id¶
The ZMQ_ROUTING_ID option shall set the routing id of the specified
socket when connecting to a ROUTER socket.
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.
If two clients use the same routing id when connecting to a
ROUTER, the results shall depend on the ZMQ_ROUTER_HANDOVER option setting.
If that is not set (or set to the default of zero), the ROUTER socket shall
reject clients trying to connect with an already-used routing id. If that
option is set to 1, the ROUTER socket shall hand-over the connection to the
new client and disconnect the existing one.
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_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 -1 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 |
-1 |
Applicable socket types |
all |
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 90% lower
depending on the flow of messages on the socket. The socket may even be able
to accept more messages than the ZMQ_SNDHWM threshold; a notable example is
for sockets using TCP transport; see zmq_tcp(7).
Option value type |
int |
Option value unit |
messages |
Default value |
1000 |
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_SOCKS_PROXY: Set SOCKS5 proxy address¶
Sets the SOCKS5 proxy address that shall be used by the socket for the TCP
connection(s). Does not support SOCKS5 authentication. If the endpoints are
domain names instead of addresses they shall not be resolved and they shall be
forwarded unchanged to the SOCKS proxy service in the client connection
request message (address type 0x03 domain name).
Option value type |
character string |
Option value unit |
N/A |
Default value |
not set |
Applicable socket types |
all, when using TCP transport |
ZMQ_STREAM_NOTIFY: send connect and disconnect notifications¶
Enables connect and disconnect notifications on a STREAM socket, when set to 1.
When notifications are enabled, the socket delivers a zero-length message when
a peer connects or disconnects.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
1 |
Applicable socket types |
ZMQ_STREAM |
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_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: Set TCP Maximum Retransmit Timeout¶
On OSes where it is supported, sets 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_TOS: Set the Type-of-Service on socket¶
Sets the ToS fields (Differentiated services (DS) and Explicit Congestion
Notification (ECN) field of the IP header. The ToS field is typically used to
specify a packets priority. The availability of this option is dependent on
intermediate network equipment that inspect the ToS field and provide a path
for low-delay, high-throughput, highly-reliable service, etc.
Option value type |
int |
Option value unit |
>0 |
Default value |
0 |
Applicable socket types |
all, only for connection-oriented
transports |
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_XPUB_VERBOSE: pass duplicate subscribe messages on XPUB socket¶
Sets the XPUB socket behaviour on new duplicated subscriptions. If
enabled, the socket passes all subscribe messages to the caller. If disabled,
only the first subscription to each filter will be passed. The default is 0
(disabled).
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
ZMQ_XPUB |
ZMQ_XPUB_VERBOSER: pass duplicate subscribe and unsubscribe messages on XPUB socket¶
Sets the XPUB socket behaviour on new duplicated subscriptions and
unsubscriptions. If enabled, the socket passes all subscribe and unsubscribe
messages to the caller. If disabled, only the first subscription to each
filter and the last unsubscription from each filter will be passed. The
default is 0 (disabled).
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
ZMQ_XPUB |
ZMQ_XPUB_MANUAL: change the subscription handling to manual¶
Sets the XPUB socket subscription handling mode manual/automatic. A value
of 0 is the default and subscription requests will be handled
automatically. A value of 1 will change the subscription requests
handling to manual, with manual mode subscription requests are not added to
the subscription list. To add subscription the user need to call setsockopt
with ZMQ_SUBSCRIBE on XPUB socket.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
ZMQ_XPUB |
ZMQ_XPUB_NODROP: do not silently drop messages if SENDHWM is reached¶
Sets the XPUB socket behaviour to return error EAGAIN if SENDHWM is
reached and the message could not be send.
A value of 0 is the default and drops the message silently when
the peers SNDHWM is reached. A value of 1 returns an EAGAIN error
code if the SNDHWM is reached and ZMQ_DONTWAIT was used.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
ZMQ_XPUB, ZMQ_PUB |
ZMQ_XPUB_WELCOME_MSG: set welcome message that will be received by subscriber when connecting¶
Sets a welcome message the will be recieved by subscriber when connecting.
Subscriber must subscribe to the Welcome message before connecting. Welcome
message will also be sent on reconnecting. For welcome message to work well
user must poll on incoming subscription messages on the XPUB socket and handle
them.
Use NULL and length of zero to disable welcome message.
Option value type |
binary data |
Option value unit |
N/A |
Default value |
NULL |
Applicable socket types |
ZMQ_XPUB |
ZMQ_ZAP_DOMAIN: Set RFC 27 authentication domain¶
Sets the domain for ZAP (ZMQ RFC 27) authentication. A ZAP domain must be
specified to enable authentication. When the ZAP domain is empty, which is the
default, ZAP authentication is disabled. This is not compatible with previous
versions of libzmq, so it can be controlled by ZMQ_ZAP_ENFORCE_DOMAIN which
for now is disabled by default. See http://rfc.zeromq.org/spec:27 for
more details.
Option value type |
character string |
Option value unit |
N/A |
Default value |
empty |
Applicable socket types |
all, when using TCP transport |
ZMQ_ZAP_ENFORCE_DOMAIN: Set ZAP domain handling to strictly adhere the RFC¶
The ZAP (ZMQ RFC 27) authentication protocol specifies that a domain must always
be set. Older versions of libzmq did not follow the spec and allowed an empty
domain to be set. This option can be used to enabled or disable the stricter,
backward incompatible behaviour. For now it is disabled by default, but in a
future version it will be enabled by default.
Option value type |
int |
Option value unit |
0, 1 |
Default value |
0 |
Applicable socket types |
all, when using ZAP |
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.
Note
This option is deprecated, please use authentication via the ZAP
API and IP address whitelisting / blacklisting.
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_IPC_FILTER_GID: Assign group ID filters to allow new IPC connections¶
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied,
then the IPC transport allows connections from any process. If at least one
UID, GID, or PID filter is applied then new connection credentials should be
matched. To clear all GID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_GID, NULL, 0).
Note
GID filters are only available on platforms supporting SO_PEERCRED
or LOCAL_PEERCRED socket options (currently only Linux and later versions of
OS X).
Note
This option is deprecated, please use authentication via the ZAP
API and IPC whitelisting / blacklisting.
Option value type |
gid_t |
Option value unit |
N/A |
Default value |
no filters (allow from all) |
Applicable socket types |
all listening sockets, when using IPC
transports. |
ZMQ_IPC_FILTER_PID: Assign process ID filters to allow new IPC connections¶
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied,
then the IPC transport allows connections from any process. If at least one
UID, GID, or PID filter is applied then new connection credentials should be
matched. To clear all PID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_PID, NULL, 0).
Note
PID filters are only available on platforms supporting the
SO_PEERCRED socket option (currently only Linux).
Note
This option is deprecated, please use authentication via the ZAP
API and IPC whitelisting / blacklisting.
Option value type |
pid_t |
Option value unit |
N/A |
Default value |
no filters (allow from all) |
Applicable socket types |
all listening sockets, when using IPC
transports. |
ZMQ_IPC_FILTER_UID: Assign user ID filters to allow new IPC connections¶
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied,
then the IPC transport allows connections from any process. If at least one
UID, GID, or PID filter is applied then new connection credentials should be
matched. To clear all UID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_UID, NULL, 0).
Note
UID filters are only available on platforms supporting SO_PEERCRED
or LOCAL_PEERCRED socket options (currently only Linux and later versions of
OS X).
Note
This option is deprecated, please use authentication via the ZAP
API and IPC whitelisting / blacklisting.
Option value type |
uid_t |
Option value unit |
N/A |
Default value |
no filters (allow from all) |
Applicable socket types |
all listening sockets, when using IPC
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_VMCI_BUFFER_SIZE: Set buffer size of the VMCI socket¶
The ZMQ_VMCI_BUFFER_SIZE option shall set 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: Set min buffer size of the VMCI socket¶
The ZMQ_VMCI_BUFFER_MIN_SIZE option shall set 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: Set max buffer size of the VMCI socket¶
The ZMQ_VMCI_BUFFER_MAX_SIZE option shall set 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: Set connection timeout of the VMCI socket¶
The ZMQ_VMCI_CONNECT_TIMEOUT option shall set 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: Control multicast local loopback¶
For multicast UDP sender sockets this option sets whether the data sent should
be looped back on local listening sockets.
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: Send connect and disconnect notifications¶
Enable connect and disconnect notifications on a ROUTER socket. When enabled,
the socket delivers a zero-length message (with routing-id as first frame)
when a peer connects or disconnects. It’s possible to notify both
events for a peer by OR-ing the flag values. This option only applies to
stream oriented (tcp, ipc) transports.
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 |
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);