Provided by: libzmq3-dev_4.3.4-6_amd64 bug

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_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 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_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.

       Option value type         int

       Option value unit         connections

       Default value             100

       Applicable socket types   all, only for
                                 connection-oriented transports

   ZMQ_BINDTODEVICE: Retrieve name of device the socket is bound to
       The ZMQ_BINDTODEVICE option retrieves the name of the device this socket is bound to, eg.
       an interface or VRF. If a socket is bound to an interface, only packets received from that
       interface are processed by the socket. If device is a VRF device, then subsequent
       binds/connects to that socket use addresses in the VRF routing table.

       Option value type         character string

       Option value unit         N/A

       Default value             not set

       Applicable socket types   all, when using TCP or UDP
                                 transports.

   ZMQ_CONNECT_TIMEOUT: Retrieve connect() timeout
       Retrieves how long to wait before timing-out a connect() system call. The connect() system
       call normally takes a long time before it returns a time out error. Setting this option
       allows the library to time out the call at an earlier interval.

       Option value type         int

       Option value unit         milliseconds

       Default value             0 (disabled)

       Applicable socket types   all, when using TCP transports.

   ZMQ_CURVE_PUBLICKEY: Retrieve current CURVE public key
       Retrieves the current long term public key for the socket. You can provide either a 32
       byte buffer, to retrieve the binary key value, or a 41 byte buffer, to retrieve the key in
       a printable Z85 format. NOTE: to fetch a printable key, the buffer must be 41 bytes large
       to hold the 40-char key value and one null byte.

       Option value type         binary data or Z85 text string

       Option value size         32 or 41

       Default value             null

       Applicable socket types   all, when using TCP transport

   ZMQ_CURVE_SECRETKEY: Retrieve current CURVE secret key
       Retrieves the current long term secret key for the socket. You can provide either a 32
       byte buffer, to retrieve the binary key value, or a 41 byte buffer, to retrieve the key in
       a printable Z85 format. NOTE: to fetch a printable key, the buffer must be 41 bytes large
       to hold the 40-char key value and one null byte.

       Option value type         binary data or Z85 text string

       Option value size         32 or 41

       Default value             null

       Applicable socket types   all, when using TCP transport

   ZMQ_CURVE_SERVERKEY: Retrieve current CURVE server key
       Retrieves the current server key for the client socket. You can provide either a 32 byte
       buffer, to retrieve the binary key value, or a 41-byte buffer, to retrieve the key in a
       printable Z85 format. NOTE: to fetch a printable key, the buffer must be 41 bytes large to
       hold the 40-char key value and one null byte.

       Option value type         binary data or Z85 text string

       Option value size         32 or 41

       Default value             null

       Applicable socket types   all, when using TCP transport

   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.

       Option value type         int

       Option value unit         N/A (flags)

       Default value             N/A

       Applicable socket types   all

   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.

           Note
           The returned file descriptor is also used internally by the zmq_send and zmq_recv
           functions. As the descriptor is edge triggered, applications must update the state of
           ZMQ_EVENTS after each invocation of zmq_send or zmq_recv.To be more explicit: after
           calling zmq_send the socket may become readable (and vice versa) without triggering a
           read event on the file descriptor.

           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.

       Option value type         int on POSIX systems, SOCKET on
                                 Windows

       Option value unit         N/A

       Default value             N/A

       Applicable socket types   all

   ZMQ_GSSAPI_PLAINTEXT: Retrieve GSSAPI plaintext or encrypted status
       Returns the ZMQ_GSSAPI_PLAINTEXT option, if any, previously set on the socket. A value of
       1 means that communications will be plaintext. A value of 0 means communications will be
       encrypted.

       Option value type         int

       Option value unit         0, 1

       Default value             0 (false)

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_GSSAPI_PRINCIPAL: Retrieve the name of the GSSAPI principal
       The ZMQ_GSSAPI_PRINCIPAL option shall retrieve the principal name set for the GSSAPI
       security mechanism. The returned value shall be a NULL-terminated string and MAY be empty.
       The returned size SHALL include the terminating null byte.

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             null string

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_GSSAPI_SERVER: Retrieve current GSSAPI server role
       Returns the ZMQ_GSSAPI_SERVER option, if any, previously set on the socket.

       Option value type         int

       Option value unit         0, 1

       Default value             0 (false)

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_GSSAPI_SERVICE_PRINCIPAL: Retrieve the name of the GSSAPI service principal
       The ZMQ_GSSAPI_SERVICE_PRINCIPAL option shall retrieve the principal name of the GSSAPI
       server to which a GSSAPI client socket intends to connect. The returned value shall be a
       NULL-terminated string and MAY be empty. The returned size SHALL include the terminating
       null byte.

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             null string

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Retrieve nametype for service principal
       Returns the ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE option, if any, previously set on the
       socket. A value of ZMQ_GSSAPI_NT_HOSTBASED (0) means the name specified with
       ZMQ_GSSAPI_SERVICE_PRINCIPAL is interpreted as a host based name. A value of
       ZMQ_GSSAPI_NT_USER_NAME (1) means it is interpreted as a local user name. A value of
       ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2) means it is interpreted as an unparsed principal name
       string (valid only with the krb5 GSSAPI mechanism).

       Option value type         int

       Option value unit         0, 1, 2

       Default value             0 (ZMQ_GSSAPI_NT_HOSTBASED)

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Retrieve nametype for service principal
       Returns the ZMQ_GSSAPI_PRINCIPAL_NAMETYPE option, if any, previously set on the socket. A
       value of ZMQ_GSSAPI_NT_HOSTBASED (0) means the name specified with ZMQ_GSSAPI_PRINCIPAL is
       interpreted as a host based name. A value of ZMQ_GSSAPI_NT_USER_NAME (1) means it is
       interpreted as a local user name. A value of ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2) means it is
       interpreted as an unparsed principal name string (valid only with the krb5 GSSAPI
       mechanism).

       Option value type         int

       Option value unit         0, 1, 2

       Default value             0 (ZMQ_GSSAPI_NT_HOSTBASED)

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_HANDSHAKE_IVL: Retrieve maximum handshake interval
       The ZMQ_HANDSHAKE_IVL option shall retrieve the maximum handshake interval for the
       specified socket. Handshaking is the exchange of socket configuration information (socket
       type, routing id, security) that occurs when a connection is first opened, only for
       connection-oriented transports. If handshaking does not complete within the configured
       time, the connection shall be closed. The value 0 means no handshake time limit.

       Option value type         int

       Option value unit         milliseconds

       Default value             30000

       Applicable socket types   all but ZMQ_STREAM, only for
                                 connection-oriented transports

   ZMQ_IDENTITY: Retrieve socket identity
       This option name is now deprecated. Use ZMQ_ROUTING_ID instead. ZMQ_IDENTITY remains as an
       alias for now.

   ZMQ_IMMEDIATE: Retrieve attach-on-connect value
       Retrieve the state of the attach on connect value. 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, primarily when using
                                 TCP/IPC transports.

   ZMQ_INVERT_MATCHING: Retrieve inverted filtering status
       Returns the value of the ZMQ_INVERT_MATCHING option. A value of 1 means the socket uses
       inverted prefix matching.

       On PUB and XPUB sockets, this causes messages to be sent to all connected sockets except
       those subscribed to a prefix that matches the message. On SUB sockets, this causes only
       incoming messages that do not match any of the socket’s subscriptions to be received by
       the user.

       Whenever ZMQ_INVERT_MATCHING is set to 1 on a PUB socket, all SUB sockets connecting to it
       must also have the option set to 1. Failure to do so will have the SUB sockets reject
       everything the PUB socket sends them. XSUB sockets do not need to do this because they do
       not filter incoming messages.

       Option value type         int

       Option value unit         0,1

       Default value             0

       Applicable socket types   ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB

   ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status
       Retrieve the IPv4-only option for the socket. This option is deprecated. Please use the
       ZMQ_IPV6 option.

       Option value type         int

       Option value unit         boolean

       Default value             1 (true)

       Applicable socket types   all, when using TCP transports.

   ZMQ_IPV6: Retrieve IPv6 socket status
       Retrieve the IPv6 option for the socket. A value of 1 means IPv6 is enabled on the socket,
       while 0 means the socket will use only IPv4. When IPv6 is enabled the socket will connect
       to, or accept connections from, both IPv4 and IPv6 hosts.

       Option value type         int

       Option value unit         boolean

       Default value             0 (false)

       Applicable socket types   all, when using TCP transports.

   ZMQ_LAST_ENDPOINT: Retrieve the last endpoint set
       The ZMQ_LAST_ENDPOINT option shall retrieve the last endpoint bound for TCP and IPC
       transports. The returned value will be a string in the form of a ZMQ DSN. Note that if the
       TCP host is INADDR_ANY, indicated by a *, then the returned address will be 0.0.0.0 (for
       IPv4). Note: not supported on GNU/Hurd with IPC due to non-working getsockname().

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             NULL

       Applicable socket types   all, when binding TCP or IPC
                                 transports

   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 zmq_close(3), and further affects the
       termination of the socket’s context with zmq_ctx_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_ctx_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_ctx_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_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.

       Option value type         int64_t

       Option value unit         bytes

       Default value             -1

       Applicable socket types   all

   ZMQ_MECHANISM: Retrieve current security mechanism
       The ZMQ_MECHANISM option shall retrieve the current security mechanism for the socket.

       Option value type         int

       Option value unit         ZMQ_NULL, ZMQ_PLAIN, ZMQ_CURVE,
                                 or ZMQ_GSSAPI

       Default value             ZMQ_NULL

       Applicable socket types   all, when using TCP or IPC
                                 transports

   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.

       Option value type         int

       Option value unit         network hops

       Default value             1

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast packets
       The ZMQ_MULTICAST_MAXTPDU option shall retrieve the maximum transport data unit size used
       for outbound multicast packets.

       This must be set at or below the minimum Maximum Transmission Unit (MTU) for all network
       paths over which multicast reception is required.

       Option value type         int

       Option value unit         bytes

       Default value             1500

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_PLAIN_PASSWORD: Retrieve current password
       The ZMQ_PLAIN_PASSWORD option shall retrieve the last password set for the PLAIN security
       mechanism. The returned value shall be a NULL-terminated string and MAY be empty. The
       returned size SHALL include the terminating null byte.

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             null string

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_PLAIN_SERVER: Retrieve current PLAIN server role
       Returns the ZMQ_PLAIN_SERVER option, if any, previously set on the socket.

       Option value type         int

       Option value unit         0, 1

       Default value             int

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_PLAIN_USERNAME: Retrieve current PLAIN username
       The ZMQ_PLAIN_USERNAME option shall retrieve the last username set for the PLAIN security
       mechanism. The returned value shall be a NULL-terminated string and MAY be empty. The
       returned size SHALL include the terminating null byte.

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             null string

       Applicable socket types   all, when using TCP or IPC
                                 transports

   ZMQ_USE_FD: Retrieve the pre-allocated socket file descriptor
       The ZMQ_USE_FD option shall retrieve the pre-allocated file descriptor that has been
       assigned to a ZMQ socket, if any. -1 shall be returned if a pre-allocated file descriptor
       was not set for the socket.

       Option value type         int

       Option value unit         file descriptor

       Default value             -1

       Applicable socket types   all bound sockets, when using
                                 IPC or TCP transport

       ZMQ_PRIORITY: Retrieve the Priority on socket

           Gets the protocol-defined priority for all packets to be sent on this
           socket, where supported by the OS.

           [horizontal]
           Option value type:: int
           Option value unit:: >0
           Default value:: 0
           Applicable socket types:: all, only for connection-oriented transports

           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.

       Option value type         int

       Option value unit         kilobits per second

       Default value             100

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_RCVBUF: Retrieve kernel receive buffer size
       The ZMQ_RCVBUF option shall retrieve the underlying kernel receive buffer size for the
       specified socket. For details refer to your operating system documentation for the
       SO_RCVBUF socket option.

       Option value type         int

       Option value unit         bytes

       Default value             8192

       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. A value of zero means no limit.

       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_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 zmq_send(3) and zmq_recv(3) for a detailed description of multi-part messages.

       Option value type         int

       Option value unit         boolean

       Default value             N/A

       Applicable socket types   all

   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.

       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. 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: 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.

       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_RECONNECT_STOP: Retrieve condition where reconnection will stop
       The ZMQ_RECONNECT_STOP option shall retrieve the conditions under which automatic
       reconnection will stop.

       The ZMQ_RECONNECT_STOP_CONN_REFUSED option will stop reconnection when 0MQ receives the
       ECONNREFUSED return code from the connect. This indicates that there is no code bound to
       the specified endpoint.

       Option value type         int

       Option value unit         ZMQ_RECONNECT_STOP_CONN_REFUSED

       Default value             0

       Applicable socket types   all, only for
                                 connection-oriented 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.

       Option value type         int

       Option value unit         milliseconds

       Default value             10000

       Applicable socket types   all, when using multicast
                                 transports

   ZMQ_ROUTING_ID: Retrieve socket routing id
       The ZMQ_ROUTING_ID option shall retrieve the routing id of the specified socket. Routing
       ids are used only by the request/reply pattern. Specifically, it can be used in tandem
       with ROUTER socket to route messages to the peer with a specific routing id.

       A routing id must be at least one byte and at most 255 bytes long. Identities starting
       with a zero byte are reserved for use by the 0MQ infrastructure.

       Option value type         binary data

       Option value unit         N/A

       Default value             NULL

       Applicable socket types   ZMQ_REP, ZMQ_REQ, ZMQ_ROUTER,
                                 ZMQ_DEALER.

   ZMQ_SNDBUF: Retrieve kernel transmit buffer size
       The ZMQ_SNDBUF option shall retrieve the underlying kernel transmit buffer size for the
       specified socket. For details refer to your operating system documentation for the
       SO_SNDBUF socket option.

       Option value type         int

       Option value unit         bytes

       Default value             8192

       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. A value of zero means no limit.

       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_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.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1 (infinite)

       Applicable socket types   all

   ZMQ_SOCKS_PROXY: Retrieve SOCKS5 proxy address
       The ZMQ_SOCKS_PROXY option shall retrieve the SOCKS5 proxy address in string format. The
       returned value shall be a NULL-terminated string and MAY be empty. The returned size SHALL
       include the terminating null byte.

       Option value type         NULL-terminated character string

       Option value unit         N/A

       Default value             null string

       Applicable socket types   all, when using TCP transports

   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_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_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
       Override TCP_KEEPIDLE(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_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_MAXRT: Retrieve Max TCP Retransmit Timeout
       On OSes where it is supported, retrieves how long before an unacknowledged TCP retransmit
       times out. The system normally attempts many TCP retransmits following an exponential
       backoff strategy. This means that after a network outage, it may take a long time before
       the session can be re-established. Setting this option allows the timeout to happen at a
       shorter interval.

       Option value type         int

       Option value unit         milliseconds

       Default value             0 (leave to OS default)

       Applicable socket types   all, when using TCP transports.

   ZMQ_THREAD_SAFE: Retrieve socket thread safety
       The ZMQ_THREAD_SAFE option shall retrieve a boolean value indicating whether or not the
       socket is threadsafe. See zmq_socket(3) for which sockets are thread-safe.

       Option value type         int

       Option value unit         boolean

       Applicable socket types   all

   ZMQ_TOS: Retrieve the Type-of-Service socket override status
       Retrieve the IP_TOS option for the socket.

       Option value type         int

       Option value unit         >0

       Default value             0

       Applicable socket types   all, only for
                                 connection-oriented transports

   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.

       Option value type         int

       Option value unit         N/A

       Default value             N/A

       Applicable socket types   all

   ZMQ_ZAP_DOMAIN: Retrieve RFC 27 authentication domain
       The ZMQ_ZAP_DOMAIN option shall retrieve the last ZAP domain set for the socket. The
       returned value shall be a NULL-terminated string and MAY be empty. An empty string means
       that ZAP authentication is disabled. The returned size SHALL include the terminating null
       byte.

       Option value type         character string

       Option value unit         N/A

       Default value             not set

       Applicable socket types   all, when using TCP transport

   ZMQ_ZAP_ENFORCE_DOMAIN: Retrieve ZAP domain handling mode
       The ZMQ_ZAP_ENFORCE_DOMAIN option shall retrieve the flag that determines whether a ZAP
       domain is strictly required or not.

       Option value type         int

       Option value unit         0, 1

       Default value             0

       Applicable socket types   all, when using ZAP

   ZMQ_VMCI_BUFFER_SIZE: Retrieve buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_SIZE option shall retrieve the size of the underlying buffer for the
       socket. Used during negotiation before the connection is established.

       Option value type         uint64_t

       Option value unit         bytes

       Default value             65546

       Applicable socket types   all, when using VMCI transport

   ZMQ_VMCI_BUFFER_MIN_SIZE: Retrieve min buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_MIN_SIZE option shall retrieve the min size of the underlying buffer
       for the socket. Used during negotiation before the connection is established.

       Option value type         uint64_t

       Option value unit         bytes

       Default value             128

       Applicable socket types   all, when using VMCI transport

   ZMQ_VMCI_BUFFER_MAX_SIZE: Retrieve max buffer size of the VMCI socket
       The ZMQ_VMCI_BUFFER_MAX_SIZE option shall retrieve the max size of the underlying buffer
       for the socket. Used during negotiation before the connection is established.

       Option value type         uint64_t

       Option value unit         bytes

       Default value             262144

       Applicable socket types   all, when using VMCI transport

   ZMQ_VMCI_CONNECT_TIMEOUT: Retrieve connection timeout of the VMCI socket
       The ZMQ_VMCI_CONNECT_TIMEOUT option shall retrieve connection timeout for the socket.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1

       Applicable socket types   all, when using VMCI transport

   ZMQ_MULTICAST_LOOP: Retrieve multicast local loopback configuration
       Retrieve the current multicast loopback configuration. A value of 1 means that the
       multicast packets sent on this socket will be looped back to local listening interface.

       Option value type         int

       Option value unit         0, 1

       Default value             1

       Applicable socket types   ZMQ_RADIO, when using UDP
                                 multicast transport

   ZMQ_ROUTER_NOTIFY: Retrieve router socket notification settings
       Retrieve the current notification settings of a router socket. The returned value is a
       bitmask composed of ZMQ_NOTIFY_CONNECT and ZMQ_NOTIFY_DISCONNECT flags, meaning connect
       and disconnect notifications are enabled, respectively. A value of 0 means the
       notifications are off.

           Note
           in DRAFT state, not yet available in stable releases.

       Option value type         int

       Option value unit         0, ZMQ_NOTIFY_CONNECT,
                                 ZMQ_NOTIFY_DISCONNECT,
                                 ZMQ_NOTIFY_CONNECT |
                                 ZMQ_NOTIFY_DISCONNECT

       Default value             0

       Applicable socket types   ZMQ_ROUTER

   ZMQ_IN_BATCH_SIZE: Maximal receive batch size
       Gets the maximal amount of messages that can be received in a single recv system call.

       Cannot be zero.

           Note
           in DRAFT state, not yet available in stable releases.

       Option value type         int

       Option value unit         messages

       Default value             8192

       Applicable socket types   All, when using TCP, IPC, PGM or
                                 NORM transport.

   ZMQ_OUT_BATCH_SIZE: Maximal send batch size
       Gets the maximal amount of messages that can be sent in a single send system call.

       Cannot be zero.

           Note
           in DRAFT state, not yet available in stable releases.

       Option value type         int

       Option value unit         messages

       Default value             8192

       Applicable socket types   All, when using TCP, IPC, PGM or
                                 NORM transport.

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

       zmq_setsockopt(3) zmq_socket(3) zmq(7)

AUTHORS

       This page was written by the 0MQ community. To make a change please read the 0MQ
       Contribution Policy at http://www.zeromq.org/docs:contributing.