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.
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.
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. 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 |
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 |
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);