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NAMEzmq_setsockopt - set 0MQ socket options SYNOPSISint 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. DESCRIPTIONThe 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 messagesThe 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.
ZMQ_RCVHWM: Set high water mark for inbound messagesThe 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.
ZMQ_AFFINITY: Set I/O thread affinityThe 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.
ZMQ_SUBSCRIBE: Establish message filterThe 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.
ZMQ_UNSUBSCRIBE: Remove message filterThe 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.
ZMQ_IDENTITY: Set socket identityThe 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.
ZMQ_RATE: Set multicast data rateThe ZMQ_RATE option shall set the maximum send or receive data rate for multicast transports such as zmq_pgm(7) using the specified socket.
ZMQ_RECOVERY_IVL: Set multicast recovery intervalThe 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.
ZMQ_SNDBUF: Set kernel transmit buffer sizeThe 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.
ZMQ_RCVBUF: Set kernel receive buffer sizeThe 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.
ZMQ_LINGER: Set linger period for socket shutdownThe 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.
ZMQ_RECONNECT_IVL: Set reconnection intervalThe 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.
ZMQ_RECONNECT_IVL_MAX: Set maximum reconnection intervalThe 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.
ZMQ_BACKLOG: Set maximum length of the queue of outstanding connectionsThe 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.
ZMQ_MAXMSGSIZE: Maximum acceptable inbound message sizeLimits 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.
ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packetsSets 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.
ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAINSets 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.
ZMQ_SNDTIMEO: Maximum time before a send operation returns with EAGAINSets 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.
ZMQ_IPV4ONLY: Use IPv4-only socketsSets 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.
ZMQ_DELAY_ATTACH_ON_CONNECT: Accept messages only when connections are madeIf 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.
ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER socketsSets 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.
ZMQ_XPUB_VERBOSE: provide all subscription messages on XPUB socketsSets 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.
ZMQ_TCP_KEEPALIVE: Override SO_KEEPALIVE socket optionOverride SO_KEEPALIVE socket option(where supported by OS). The default value of -1 means to skip any overrides and leave it to OS default.
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.
ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket optionOverride TCP_KEEPCNT socket option(where supported by OS). The default value of -1 means to skip any overrides and leave it to OS default.
ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket optionOverride TCP_KEEPINTVL socket option(where supported by OS). The default value of -1 means to skip any overrides and leave it to OS default.
ZMQ_TCP_ACCEPT_FILTER: Assign filters to allow new TCP connectionsAssign 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.
RETURN VALUEThe zmq_setsockopt() function shall return zero if successful. Otherwise it shall return -1 and set errno to one of the values defined below. ERRORSEINVAL 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.
EXAMPLESubscribing 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 ALSOzmq_getsockopt(3) zmq_socket(3) zmq(7) AUTHORSThis 0MQ manual page was written by Martin Sustrik <sustrik@250bpm.com[1]> and Martin Lucina <mato@kotelna.sk[2]>. NOTES
mailto:sustrik@250bpm.com
mailto:mato@kotelna.sk
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