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 and ZMQ_XPUB_VERBOSE only take effect for
subsequent socket bind/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.
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.
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. Socket identity is used only by request/reply pattern. Namely,
it can be used in tandem with ROUTER socket to route messages to the peer with
specific identity.
Identity should be at least one byte and at most 255 bytes long. Identities
starting with binary zero are reserved for use by 0MQ infrastructure.
If two peers use the same identity when connecting to a third peer, the results
shall be undefined.
Option value type |
binary data |
Option value unit |
N/A |
Default value |
NULL |
Applicable socket types |
all |
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_IPV4ONLY: Use IPv4-only sockets¶
Sets the underlying native socket type. A value of 1 will use IPv4 sockets,
while the value of 0 will use IPv6 sockets. An IPv6 socket lets applications
connect to and accept connections from both IPv4 and IPv6 hosts.
Option value type |
int |
Option value unit |
boolean |
Default value |
1 (true) |
Applicable socket types |
all, when using TCP transports. |
ZMQ_DELAY_ATTACH_ON_CONNECT: Accept messages only when
connections are made¶
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, 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_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_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 arbitrary number of filters that will be applied for each new TCP
transport connection on a listening socket. If no filters applied, then TCP
transport allows connections from any ip. 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. |
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(7)
AUTHORS¶
This 0MQ manual page was written by Martin Sustrik <
sustrik@250bpm.com[1]> and Martin Lucina <
mato@kotelna.sk[2]>.
NOTES¶
- 1.
- sustrik@250bpm.com
mailto:sustrik@250bpm.com
- 2.
- mato@kotelna.sk
mailto:mato@kotelna.sk