Provided by: libzmq-dev_2.1.11-1ubuntu1_amd64 bug

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 and ZMQ_LINGER,
       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_HWM: Set high water mark
       The ZMQ_HWM option shall set the high water mark for 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.

       The default ZMQ_HWM value of zero means "no limit".

       Option value type         uint64_t

       Option value unit         messages

       Default value             0

       Applicable socket types   all

   ZMQ_SWAP: Set disk offload size
       The ZMQ_SWAP option shall set the disk offload (swap) size for the specified socket. A
       socket which has ZMQ_SWAP set to a non-zero value may exceed its high water mark; in this
       case outstanding messages shall be offloaded to storage on disk rather than held in
       memory.

       The value of ZMQ_SWAP defines the maximum size of the swap space in bytes.

       Option value type         int64_t

       Option value unit         bytes

       Default value             0

       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_IDENTITY: Set socket identity
       The ZMQ_IDENTITY option shall set the identity of the specified socket. Socket identity
       determines if existing 0MQ infrastructure (message queues, forwarding devices) shall be
       identified with a specific application and persist across multiple runs of the
       application.

       If the socket has no identity, each run of an application is completely separate from
       other runs. However, with identity set the socket shall re-use any existing 0MQ
       infrastructure configured by the previous run(s). Thus the application may receive
       messages that were sent in the meantime, message queue limits shall be shared with
       previous run(s) and so on.

       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.

       Option value type         binary data

       Option value unit         N/A

       Default value             NULL

       Applicable socket types   all

   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_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         int64_t

       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 seconds 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         int64_t

       Option value unit         seconds

       Default value             10

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_RECOVERY_IVL_MSEC: Set multicast recovery interval in milliseconds
       The ZMQ_RECOVERY_IVL_MSEC option shall set the recovery interval, specified in
       milliseconds (ms) 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.

       A non-zero value of the ZMQ_RECOVERY_IVL_MSEC option will take precedence over the
       ZMQ_RECOVERY_IVL option, but since the default for the ZMQ_RECOVERY_IVL_MSEC is -1, the
       default is to use the ZMQ_RECOVERY_IVL option value.

           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         int64_t

       Option value unit         milliseconds

       Default value             -1

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_MCAST_LOOP: Control multicast loop-back
       The ZMQ_MCAST_LOOP option shall control whether data sent via multicast transports using
       the specified socket can also be received by the sending host via loop-back. A value of
       zero disables the loop-back functionality, while the default value of 1 enables the
       loop-back functionality. Leaving multicast loop-back enabled when it is not required can
       have a negative impact on performance. Where possible, disable ZMQ_MCAST_LOOP in
       production environments.

       Option value type         int64_t

       Option value unit         boolean

       Default value             1

       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         uint64_t

       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         uint64_t

       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.

           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.

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