ZMQ_SETSOCKOPT(3)                 0MQ Manual                 ZMQ_SETSOCKOPT(3)



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 it's 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:

       o   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.

       o   The value of 0 specifies no linger period. Pending messages shall
           be discarded immediately when the socket is closed with
           zmq_close().

       o   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



0MQ 2.1.6                         05/07/2011                 ZMQ_SETSOCKOPT(3)
