Ubuntu Manpage: zmq_getsockopt - get 0MQ socket options

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Provided by: libzmq3-dev_4.2.5-1ubuntu0.2_amd64

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.

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

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).

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

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).

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

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).

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_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_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.

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. Currently ZMQ_CLIENT and ZMQ_SERVER sockets are threadsafe.

Option value type 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

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);

AUTHORS

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NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

EXAMPLE

SEE ALSO

AUTHORS