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-zmq_getsockopt(3)
-=================
-
-
-NAME
-----
-
-zmq_getsockopt - get 0MQ socket options
-
-
-SYNOPSIS
---------
-*int zmq_getsockopt (void '*socket', int 'option_name', void '*option_value', size_t '*option_len');*
-
-
-DESCRIPTION
------------
-The _zmq_getsockopt()_ function shall retrieve the value for the option
-specified by the 'option_name' argument for the 0MQ socket pointed to by the
-'socket' argument, and store it in the buffer pointed to by the 'option_value'
-argument. The 'option_len' argument is the size in bytes of the buffer pointed
-to by 'option_value'; upon successful completion _zmq_getsockopt()_ shall
-modify the 'option_len' argument to indicate the actual size of the option
-value stored in the buffer.
-
-The following options can be retrieved with the _zmq_getsockopt()_ function:
-
-
-ZMQ_TYPE: Retrieve socket type
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_TYPE' option shall retrieve the socket type for the specified
-'socket'. The socket type is specified at socket creation time and
-cannot be modified afterwards.
-
-[horizontal]
-Option value type:: int
-Option value unit:: N/A
-Default value:: N/A
-Applicable socket types:: all
-
-
-ZMQ_RCVMORE: More message data parts to follow
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RCVMORE' option shall return True (1) if the message part last
-received from the 'socket' was a data part with more parts to follow. If there
-are no data parts to follow, this option shall return False (0).
-
-Refer to linkzmq:zmq_send[3] and linkzmq:zmq_recv[3] for a detailed description
-of multi-part messages.
-
-[horizontal]
-Option value type:: int
-Option value unit:: boolean
-Default value:: N/A
-Applicable socket types:: all
-
-
-ZMQ_SNDHWM: Retrieves high water mark for outbound messages
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_SNDHWM' option shall return 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 linkzmq:zmq_socket[3] for details on the exact action taken for each socket
-type.
-
-[horizontal]
-Option value type:: int
-Option value unit:: messages
-Default value:: 1000
-Applicable socket types:: all
-
-
-ZMQ_RCVHWM: Retrieve high water mark for inbound messages
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RCVHWM' option shall return 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 linkzmq:zmq_socket[3] for details on the exact action taken for each socket
-type.
-
-[horizontal]
-Option value type:: int
-Option value unit:: messages
-Default value:: 1000
-Applicable socket types:: all
-
-
-ZMQ_AFFINITY: Retrieve I/O thread affinity
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_AFFINITY' option shall retrieve 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 linkzmq:zmq_init[3] for details on allocating the number of I/O
-threads for a specific _context_.
-
-[horizontal]
-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 retrieve 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.
-
-[horizontal]
-Option value type:: binary data
-Option value unit:: N/A
-Default value:: NULL
-Applicable socket types:: all
-
-
-ZMQ_RATE: Retrieve multicast data rate
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RATE' option shall retrieve the maximum send or receive data rate for
-multicast transports using the specified 'socket'.
-
-[horizontal]
-Option value type:: int
-Option value unit:: kilobits per second
-Default value:: 100
-Applicable socket types:: all, when using multicast transports
-
-
-ZMQ_RECOVERY_IVL: Get multicast recovery interval
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RECOVERY_IVL' option shall retrieve 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: 10000
-Applicable socket types:: all, when using multicast transports
-
-
-ZMQ_SNDBUF: Retrieve kernel transmit buffer size
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_SNDBUF' option shall retrieve the underlying kernel transmit buffer
-size for the specified 'socket'. A value of zero means that the OS default is
-in effect. For details refer to your operating system documentation for the
-'SO_SNDBUF' socket option.
-
-[horizontal]
-Option value type:: int
-Option value unit:: bytes
-Default value:: 0
-Applicable socket types:: all
-
-
-ZMQ_RCVBUF: Retrieve kernel receive buffer size
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RCVBUF' option shall retrieve the underlying kernel receive buffer
-size for the specified 'socket'. A value of zero means that the OS default is
-in effect. For details refer to your operating system documentation for the
-'SO_RCVBUF' socket option.
-
-[horizontal]
-Option value type:: int
-Option value unit:: bytes
-Default value:: 0
-Applicable socket types:: all
-
-
-ZMQ_LINGER: Retrieve linger period for socket shutdown
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_LINGER' option shall retrieve 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
-linkzmq:zmq_close[3], and further affects the termination of the socket's
-context with linkzmq: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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: -1 (infinite)
-Applicable socket types:: all
-
-
-ZMQ_RECONNECT_IVL: Retrieve reconnection interval
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RECONNECT_IVL' option shall retrieve 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: 100
-Applicable socket types:: all, only for connection-oriented transports
-
-
-ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_RECONNECT_IVL_MAX' option shall retrieve 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: 0 (only use ZMQ_RECONNECT_IVL)
-Applicable socket types:: all, only for connection-oriented transport
-
-
-ZMQ_BACKLOG: Retrieve maximum length of the queue of outstanding connections
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_BACKLOG' option shall retrieve 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.
-
-[horizontal]
-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
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The option shall retrieve limit for the inbound messages. If a peer sends
-a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
-'no limit'.
-
-[horizontal]
-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
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The option shall retrieve time-to-live used for outbound multicast packets.
-The default of 1 means that the multicast packets don't leave the local network.
-
-[horizontal]
-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 socket operation returns with EAGAIN
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Retrieve the timeout for recv 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: -1 (infinite)
-Applicable socket types:: all
-
-
-ZMQ_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Retrieve 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: milliseconds
-Default value:: -1 (infinite)
-Applicable socket types:: all
-
-
-ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Retrieve 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.
-
-[horizontal]
-Option value type:: int
-Option value unit:: boolean
-Default value:: 1 (true)
-Applicable socket types:: all, when using TCP transports.
-
-
-ZMQ_FD: Retrieve file descriptor associated with the socket
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_FD' option shall retrieve the file descriptor associated with the
-specified 'socket'. The returned file descriptor can be used to integrate the
-socket into an existing event loop; the 0MQ library shall signal any pending
-events on the socket in an _edge-triggered_ fashion by making the file
-descriptor become ready for reading.
-
-NOTE: The ability to read from the returned file descriptor does not
-necessarily indicate that messages are available to be read from, or can be
-written to, the underlying socket; applications must retrieve the actual event
-state with a subsequent retrieval of the 'ZMQ_EVENTS' option.
-
-CAUTION: The returned file descriptor is intended for use with a 'poll' or
-similar system call only. Applications must never attempt to read or write data
-to it directly, neither should they try to close it.
-
-[horizontal]
-Option value type:: int on POSIX systems, SOCKET on Windows
-Option value unit:: N/A
-Default value:: N/A
-Applicable socket types:: all
-
-
-ZMQ_EVENTS: Retrieve socket event state
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The 'ZMQ_EVENTS' option shall retrieve the event state for the specified
-'socket'. The returned value is a bit mask constructed by OR'ing a combination
-of the following event flags:
-
-*ZMQ_POLLIN*::
-Indicates that at least one message may be received from the specified socket
-without blocking.
-
-*ZMQ_POLLOUT*::
-Indicates that at least one message may be sent to the specified socket without
-blocking.
-
-The combination of a file descriptor returned by the 'ZMQ_FD' option being
-ready for reading but no actual events returned by a subsequent retrieval of
-the 'ZMQ_EVENTS' option is valid; applications should simply ignore this case
-and restart their polling operation/event loop.
-
-[horizontal]
-Option value type:: int
-Option value unit:: N/A (flags)
-Default value:: N/A
-Applicable socket types:: all
-
-
-RETURN VALUE
-------------
-The _zmq_getsockopt()_ 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, or the size of the buffer pointed to by
-_option_value_, as specified by _option_len_, is insufficient for storing the
-option value.
-*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
--------
-.Retrieving the high water mark for outgoing messages
-----
-/* Retrieve high water mark into sndhwm */
-int sndhwm;
-size_t sndhwm_size = sizeof (sndhwm);
-rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
-assert (rc == 0);
-----
-
-
-SEE ALSO
---------
-linkzmq:zmq_setsockopt[3]
-linkzmq:zmq_socket[3]
-linkzmq:zmq[7]
-
-
-AUTHORS
--------
-The 0MQ documentation was written by Martin Sustrik <sustrik@250bpm.com> and
-Martin Lucina <martin@lucina.net>.