zmq_getsockopt.txt 35.6 KB
Newer Older
Martin Lucina's avatar
Martin Lucina committed
1 2 3 4 5 6 7 8 9 10 11 12
zmq_getsockopt(3)
=================


NAME
----

zmq_getsockopt - get 0MQ socket options


SYNOPSIS
--------
Martin Lucina's avatar
Martin Lucina committed
13
*int zmq_getsockopt (void '*socket', int 'option_name', void '*option_value', size_t '*option_len');*
Martin Lucina's avatar
Martin Lucina committed
14 15 16 17 18 19 20 21


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
Martin Lucina's avatar
Martin Lucina committed
22
to by 'option_value'; upon successful completion _zmq_getsockopt()_ shall
23
modify the 'option_len' argument to indicate the actual size of the option
Martin Lucina's avatar
Martin Lucina committed
24
value stored in the buffer.
Martin Lucina's avatar
Martin Lucina committed
25 26 27 28

The following options can be retrieved with the _zmq_getsockopt()_ function:


29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57
ZMQ_AFFINITY: Retrieve I/O thread affinity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_AFFINITY' option shall retrieve the I/O thread affinity for newly
created connections on the specified 'socket'.

Affinity determines which threads from the 0MQ I/O thread pool associated with
the socket's _context_ shall handle newly created connections.  A value of zero
specifies no affinity, meaning that work shall be distributed fairly among all
0MQ I/O threads in the thread pool. For non-zero values, the lowest bit
corresponds to thread 1, second lowest bit to thread 2 and so on.  For example,
a value of 3 specifies that subsequent connections on 'socket' shall be handled
exclusively by I/O threads 1 and 2.

See also linkzmq:zmq_init[3] for details on allocating the number of I/O
threads for a specific _context_.

[horizontal]
Option value type:: uint64_t
Option value unit:: N/A (bitmap)
Default value:: 0
Applicable socket types:: N/A


ZMQ_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.
58 59 60

[horizontal]
Option value type:: int
61 62 63
Option value unit:: connections
Default value:: 100
Applicable socket types:: all, only for connection-oriented transports
64 65


66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
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.

[horizontal]
Option value type:: character string
Option value unit:: N/A
Default value:: not set
Applicable socket types:: all, when using TCP or UDP transports.


KIU Shueng Chuan's avatar
KIU Shueng Chuan committed
81 82 83 84 85 86 87 88 89 90 91 92 93 94
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.

[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0 (disabled)
Applicable socket types:: all, when using TCP transports.


95 96
ZMQ_CURVE_PUBLICKEY: Retrieve current CURVE public key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
97

98 99 100 101 102
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.
103 104

[horizontal]
105 106 107 108
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
109 110


111 112
ZMQ_CURVE_SECRETKEY: Retrieve current CURVE secret key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
113

114 115 116
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.
117 118
NOTE: to fetch a printable key, the buffer must be 41 bytes large
to hold the 40-char key value and one null byte.
Martin Lucina's avatar
Martin Lucina committed
119

120
[horizontal]
121 122 123 124
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
125 126


127 128
ZMQ_CURVE_SERVERKEY: Retrieve current CURVE server key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
129

130 131
Retrieves the current server key for the client socket. You can
provide either a 32 byte buffer, to retrieve the binary key value, or
132 133 134
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.
135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160

[horizontal]
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.
161

162
[horizontal]
163
Option value type:: int
164 165
Option value unit:: N/A (flags)
Default value:: N/A
Martin Lucina's avatar
Martin Lucina committed
166 167 168
Applicable socket types:: all


169 170 171 172 173 174 175
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.
Martin Lucina's avatar
Martin Lucina committed
176

177 178 179 180
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.
Martin Lucina's avatar
Martin Lucina committed
181

182 183 184 185 186 187 188 189 190 191
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.
Martin Lucina's avatar
Martin Lucina committed
192

193
[horizontal]
194 195 196 197
Option value type:: int on POSIX systems, SOCKET on Windows
Option value unit:: N/A
Default value:: N/A
Applicable socket types:: all
Martin Lucina's avatar
Martin Lucina committed
198

199

200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249
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.

[horizontal]
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.

[horizontal]
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.

[horizontal]
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.

[horizontal]
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

250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280
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).

[horizontal]
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).

[horizontal]
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
281

282 283 284 285
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
286
information (socket type, routing id, security) that occurs when a connection
287 288 289 290 291 292 293 294 295 296 297
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.

[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 30000
Applicable socket types:: all but ZMQ_STREAM, only for connection-oriented transports


298 299
ZMQ_IDENTITY: Retrieve socket identity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
300 301
This option name is now deprecated. Use ZMQ_ROUTING_ID instead. 
ZMQ_IDENTITY remains as an alias for now. 
302

303

304 305 306 307 308 309
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.
Martin Lucina's avatar
Martin Lucina committed
310

311
[horizontal]
312
Option value type:: int
313 314 315
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, primarily when using TCP/IPC transports.
Martin Lucina's avatar
Martin Lucina committed
316 317


318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340
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.

[horizontal]
Option value type:: int
Option value unit:: 0,1
Default value:: 0
Applicable socket types:: ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB


341 342 343 344
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.
Martin Lucina's avatar
Martin Lucina committed
345

346
[horizontal]
347
Option value type:: int
348 349 350
Option value unit:: boolean
Default value:: 1 (true)
Applicable socket types:: all, when using TCP transports.
351 352


353 354 355 356 357 358
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.
Martin Lucina's avatar
Martin Lucina committed
359

360
[horizontal]
361
Option value type:: int
362 363 364
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, when using TCP transports.
Martin Lucina's avatar
Martin Lucina committed
365 366


367 368 369 370 371 372
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).
Martin Lucina's avatar
Martin Lucina committed
373

374
[horizontal]
375 376 377 378
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
Martin Lucina's avatar
Martin Lucina committed
379 380


381 382
ZMQ_LINGER: Retrieve linger period for socket shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
383 384 385 386
The 'ZMQ_LINGER' option shall retrieve the linger period for the specified
'socket'.  The linger period determines how long pending messages which have
yet to be sent to a peer shall linger in memory after a socket is closed with
linkzmq:zmq_close[3], and further affects the termination of the socket's
387
context with linkzmq:zmq_ctx_term[3]. The following outlines the different
388 389 390 391
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
392
  terminate the socket's context with _zmq_ctx_term()_ shall block until all
393 394 395 396 397 398 399
  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()_;
400
  attempting to terminate the socket's context with _zmq_ctx_term()_ shall block
401 402
  until either all pending messages have been sent to a peer, or the linger
  period expires, after which any pending messages shall be discarded.
403 404 405 406

[horizontal]
Option value type:: int
Option value unit:: milliseconds
407
Default value:: -1 (infinite)
408 409
Applicable socket types:: all

410

411 412
ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
413
The option shall retrieve limit for the inbound messages. If a peer sends
414 415 416 417 418 419 420 421 422 423
a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
'no limit'.

[horizontal]
Option value type:: int64_t
Option value unit:: bytes
Default value:: -1
Applicable socket types:: all


424 425 426 427 428 429 430
ZMQ_MECHANISM: Retrieve current security mechanism
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MECHANISM' option shall retrieve the current security mechanism
for the socket.

[horizontal]
Option value type:: int
431
Option value unit:: ZMQ_NULL, ZMQ_PLAIN, ZMQ_CURVE, or ZMQ_GSSAPI
432 433 434 435
Default value:: ZMQ_NULL
Applicable socket types:: all, when using TCP or IPC transports


436 437
ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
438
The option shall retrieve time-to-live used for outbound multicast packets.
439 440 441 442 443 444 445 446 447
The default of 1 means that the multicast packets don't leave the local network.

[horizontal]
Option value type:: int
Option value unit:: network hops
Default value:: 1
Applicable socket types:: all, when using multicast transports


448 449 450 451 452 453 454 455 456 457 458 459 460 461 462
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.

[horizontal]
Option value type:: int
Option value unit:: bytes
Default value:: 1500
Applicable socket types:: all, when using multicast transports


463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479
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.

[horizontal]
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.
480 481 482

[horizontal]
Option value type:: int
483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501
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.

[horizontal]
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


502
ZMQ_USE_FD: Retrieve the pre-allocated socket file descriptor
503
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
504
The 'ZMQ_USE_FD' option shall retrieve the pre-allocated file
505 506 507 508 509 510 511 512 513 514
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.

[horizontal]
Option value type:: int
Option value unit:: file descriptor
Default value:: -1
Applicable socket types:: all bound sockets, when using IPC or TCP transport


515 516 517 518 519 520 521 522 523 524 525 526 527 528 529
ZMQ_RATE: Retrieve multicast data rate
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RATE' option shall retrieve the maximum send or receive data rate for
multicast transports using the specified 'socket'.

[horizontal]
Option value type:: int
Option value unit:: kilobits per second
Default value:: 100
Applicable socket types:: all, when using multicast transports


ZMQ_RCVBUF: Retrieve kernel receive buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVBUF' option shall retrieve the underlying kernel receive buffer
530 531
size for the specified 'socket'. For details refer to your operating system
documentation for the 'SO_RCVBUF' socket option.
532 533 534 535

[horizontal]
Option value type:: int
Option value unit:: bytes
536
Default value:: 8192
537 538 539
Applicable socket types:: all


540 541 542 543 544 545 546 547 548 549 550 551 552
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 linkzmq:zmq_socket[3] for details on the exact action taken for each socket
type.
553 554 555

[horizontal]
Option value type:: int
556 557
Option value unit:: messages
Default value:: 1000
558 559 560
Applicable socket types:: all


561 562 563 564 565 566 567 568
ZMQ_RCVMORE: More message data parts to follow
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVMORE' option shall return True (1) if the message part last
received from the 'socket' was a data part with more parts to follow. If there
are no data parts to follow, this option shall return False (0).

Refer to linkzmq:zmq_send[3] and linkzmq:zmq_recv[3] for a detailed description
of multi-part messages.
Pieter Hintjens's avatar
Pieter Hintjens committed
569 570 571 572

[horizontal]
Option value type:: int
Option value unit:: boolean
573 574
Default value:: N/A
Applicable socket types:: all
Pieter Hintjens's avatar
Pieter Hintjens committed
575 576


577 578 579 580 581 582 583
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.
Steven McCoy's avatar
Steven McCoy committed
584 585 586

[horizontal]
Option value type:: int
587 588 589
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
Steven McCoy's avatar
Steven McCoy committed
590 591


592 593 594 595 596 597 598 599 600
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.
601 602 603

[horizontal]
Option value type:: int
604 605
Option value unit:: milliseconds
Default value:: 100
606 607 608
Applicable socket types:: all, only for connection-oriented transports


609 610 611 612 613 614 615 616 617 618 619
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.
620 621 622

[horizontal]
Option value type:: int
623 624 625
Option value unit:: milliseconds
Default value:: 0 (only use ZMQ_RECONNECT_IVL)
Applicable socket types:: all, only for connection-oriented transport
626 627


628 629 630 631 632 633
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.
634

635 636 637 638 639
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 10000
Applicable socket types:: all, when using multicast transports
640

641

642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658
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.

[horizontal]
Option value type:: binary data
Option value unit:: N/A
Default value:: NULL
Applicable socket types:: ZMQ_REP, ZMQ_REQ, ZMQ_ROUTER, ZMQ_DEALER.


659 660 661
ZMQ_SNDBUF: Retrieve kernel transmit buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SNDBUF' option shall retrieve the underlying kernel transmit buffer
662 663
size for the specified 'socket'. For details refer to your operating system
documentation for the 'SO_SNDBUF' socket option.
664 665

[horizontal]
666 667
Option value type:: int
Option value unit:: bytes
668
Default value:: 8192
669 670 671
Applicable socket types:: all


672 673 674 675 676 677 678
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.
679

680 681 682 683 684
If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, 0MQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket descriptions
in linkzmq:zmq_socket[3] for details on the exact action taken for each socket
type.
685 686

[horizontal]
687
Option value type:: int
688 689
Option value unit:: messages
Default value:: 1000
690 691
Applicable socket types:: all

692

693 694 695 696 697 698 699
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.
700 701

[horizontal]
702 703 704 705
Option value type:: int
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
706

707

708 709 710 711 712 713 714 715 716 717 718 719 720
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.

[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP transports


721 722 723 724
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.
725 726 727 728

[horizontal]
Option value type:: int
Option value unit:: -1,0,1
729
Default value:: -1 (leave to OS default)
730 731
Applicable socket types:: all, when using TCP transports.

732

733 734 735 736
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.
737 738 739 740

[horizontal]
Option value type:: int
Option value unit:: -1,>0
741
Default value:: -1 (leave to OS default)
742 743
Applicable socket types:: all, when using TCP transports.

744

745
ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
746
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
747
Override 'TCP_KEEPIDLE'(or 'TCP_KEEPALIVE' on some OS) socket option (where
748 749
supported by OS). The default value of `-1` means to skip any overrides and
leave it to OS default.
750 751 752 753

[horizontal]
Option value type:: int
Option value unit:: -1,>0
754
Default value:: -1 (leave to OS default)
755 756
Applicable socket types:: all, when using TCP transports.

757

758 759 760 761
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.
762 763 764 765

[horizontal]
Option value type:: int
Option value unit:: -1,>0
766
Default value:: -1 (leave to OS default)
767 768
Applicable socket types:: all, when using TCP transports.

Pieter Hintjens's avatar
Pieter Hintjens committed
769

770 771
ZMQ_TCP_MAXRT: Retrieve Max TCP Retransmit Timeout
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
772
On OSes where it is supported, retrieves how long before an unacknowledged TCP
773 774 775 776
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.
777 778 779 780 781 782 783 784

[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0 (leave to OS default)
Applicable socket types:: all, when using TCP transports.


785 786 787
ZMQ_THREAD_SAFE: Retrieve socket thread safety
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_THREAD_SAFE' option shall retrieve a boolean value indicating whether
788 789
or not the socket is threadsafe. Currently 'ZMQ_CLIENT' and 'ZMQ_SERVER' sockets
are threadsafe.
790 791 792 793 794 795

[horizontal]
Option value type:: boolean
Applicable socket types:: all


796 797 798
ZMQ_TOS: Retrieve the Type-of-Service socket override status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the IP_TOS option for the socket.
799 800 801

[horizontal]
Option value type:: int
802 803 804
Option value unit:: >0
Default value:: 0
Applicable socket types:: all, only for connection-oriented transports
805 806


807 808 809 810 811
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.
812 813 814 815

[horizontal]
Option value type:: int
Option value unit:: N/A
816 817
Default value:: N/A
Applicable socket types:: all
Pieter Hintjens's avatar
Pieter Hintjens committed
818 819


820 821 822 823 824
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
825 826
be empty. An empty string means that ZAP authentication is disabled. 
The returned size SHALL include the terminating null byte.
827 828 829 830 831 832 833 834

[horizontal]
Option value type:: character string
Option value unit:: N/A
Default value:: not set
Applicable socket types:: all, when using TCP transport


835 836 837 838 839 840 841 842 843 844 845 846
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.

[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: all, when using ZAP


Ilya Kulakov's avatar
Ilya Kulakov committed
847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894
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.

[horizontal]
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.

[horizontal]
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.

[horizontal]
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.

[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: -1
Applicable socket types:: all, when using VMCI transport


895 896 897 898 899 900 901 902 903 904 905 906
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.

[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 1
Applicable socket types:: ZMQ_RADIO, when using UDP multicast transport

907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923

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.

[horizontal]
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


Martin Lucina's avatar
Martin Lucina committed
924 925 926 927 928 929 930 931 932 933 934 935 936 937 938
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.
939 940
*ENOTSOCK*::
The provided 'socket' was invalid.
941 942
*EINTR*::
The operation was interrupted by delivery of a signal.
Martin Lucina's avatar
Martin Lucina committed
943 944 945 946


EXAMPLE
-------
Pieter Hintjens's avatar
Pieter Hintjens committed
947
.Retrieving the high water mark for outgoing messages
Martin Lucina's avatar
Martin Lucina committed
948
----
Pieter Hintjens's avatar
Pieter Hintjens committed
949
/* Retrieve high water mark into sndhwm */
950 951 952
int sndhwm;
size_t sndhwm_size = sizeof (sndhwm);
rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
Martin Lucina's avatar
Martin Lucina committed
953 954 955 956 957 958 959 960 961 962 963
assert (rc == 0);
----


SEE ALSO
--------
linkzmq:zmq_setsockopt[3]
linkzmq:zmq_socket[3]
linkzmq:zmq[7]


964 965
AUTHORS
-------
966 967
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>.