zmq_setsockopt.txt 51.9 KB
Newer Older
1 2 3 4 5 6 7
zmq_setsockopt(3)
=================


NAME
----

Martin Lucina's avatar
Martin Lucina committed
8
zmq_setsockopt - set 0MQ socket options
9 10 11 12


SYNOPSIS
--------
Martin Lucina's avatar
Martin Lucina committed
13
*int zmq_setsockopt (void '*socket', int 'option_name', const void '*option_value', size_t 'option_len');*
14

Kobolog's avatar
Kobolog committed
15
Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE,
16
ZMQ_LINGER, ZMQ_ROUTER_HANDOVER, ZMQ_ROUTER_MANDATORY, ZMQ_PROBE_ROUTER,
17
ZMQ_XPUB_VERBOSE, ZMQ_XPUB_VERBOSER, ZMQ_REQ_CORRELATE,
18 19
ZMQ_REQ_RELAXED, ZMQ_SNDHWM and ZMQ_RCVHWM, only take effect for
subsequent socket bind/connects.
Pieter Hintjens's avatar
Pieter Hintjens committed
20 21 22

Specifically, security options take effect for subsequent bind/connect calls,
and can be changed at any time to affect subsequent binds and/or connects.
23 24 25

DESCRIPTION
-----------
Martin Lucina's avatar
Martin Lucina committed
26 27 28
The _zmq_setsockopt()_ function shall set the option specified by the
'option_name' argument to the value pointed to by the 'option_value' argument
for the 0MQ socket pointed to by the 'socket' argument. The 'option_len'
29 30 31
argument is the size of the option value in bytes. For options taking a value of
type "character string", the provided byte data should either contain no zero
bytes, or end in a single zero byte (terminating ASCII NUL character).
Martin Lucina's avatar
Martin Lucina committed
32

Martin Lucina's avatar
Martin Lucina committed
33
The following socket options can be set with the _zmq_setsockopt()_ function:
Martin Lucina's avatar
Martin Lucina committed
34 35 36 37


ZMQ_AFFINITY: Set I/O thread affinity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Martin Lucina's avatar
Martin Lucina committed
38 39
The 'ZMQ_AFFINITY' option shall set the I/O thread affinity for newly created
connections on the specified 'socket'.
Martin Lucina's avatar
Martin Lucina committed
40

41 42 43 44 45 46 47
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.
Martin Lucina's avatar
Martin Lucina committed
48 49 50 51

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

52
[horizontal]
53
Option value type:: uint64_t
Martin Lucina's avatar
Martin Lucina committed
54 55 56 57 58
Option value unit:: N/A (bitmap)
Default value:: 0
Applicable socket types:: N/A


59 60 61 62 63 64
ZMQ_BACKLOG: Set maximum length of the queue of outstanding connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_BACKLOG' option shall set 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.
Martin Lucina's avatar
Martin Lucina committed
65

66 67 68 69 70 71 72
[horizontal]
Option value type:: int
Option value unit:: connections
Default value:: 100
Applicable socket types:: all, only for connection-oriented transports.


73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
ZMQ_BINDTODEVICE: Set name of device to bind the socket to
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_BINDTODEVICE' option binds this socket to a particular device, eg.
an interface or VRF. If a socket is bound to an interface, only packets
received from that particular 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: requires setting CAP_NET_RAW on the compiled program.

[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.


90 91
ZMQ_CONNECT_RID: Assign the next outbound connection id 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
92 93
This option name is now deprecated. Use ZMQ_CONNECT_ROUTING_ID instead. 
ZMQ_CONNECT_RID remains as an alias for now. 
94

95 96 97 98 99 100 101 102 103 104 105 106

ZMQ_CONNECT_ROUTING_ID: Assign the next outbound routing id 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_CONNECT_ROUTING_ID' option sets the peer id of the peer connected 
via the next zmq_connect() call, such that that connection is immediately ready for 
data transfer with the given routing id.  This option applies only to the first
subsequent call to zmq_connect(), zmq_connect() calls thereafter use the default 
connection behaviour. 

Typical use is to set this socket option ahead of each zmq_connect() call. 
Each connection MUST be assigned a unique routing id. Assigning a 
routing id that is already in use is not allowed. 
107 108

Useful when connecting ROUTER to ROUTER, or STREAM to STREAM, as it 
109
allows for immediate sending to peers. Outbound routing id framing requirements 
110 111
for ROUTER and STREAM sockets apply.

112 113 114
The routing id must be from 1 to 255 bytes long and MAY NOT start with 
a zero byte (such routing ids are reserved for internal use by the 0MQ 
infrastructure).
115 116 117 118 119 120 121 122

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


123 124 125 126
ZMQ_CONFLATE: Keep only last message
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If set, a socket shall keep only one message in its inbound/outbound
queue, this message being the last message received/the last message
127
to be sent. Ignores 'ZMQ_RCVHWM' and 'ZMQ_SNDHWM' options. Does not
128 129
support multi-part messages, in particular, only one part of it is kept
in the socket internal queue.
Martin Lucina's avatar
Martin Lucina committed
130

131
[horizontal]
132 133 134 135
Option value type:: int
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: ZMQ_PULL, ZMQ_PUSH, ZMQ_SUB, ZMQ_PUB, ZMQ_DEALER
Martin Lucina's avatar
Martin Lucina committed
136 137


KIU Shueng Chuan's avatar
KIU Shueng Chuan committed
138 139 140 141 142 143 144 145 146 147 148 149 150 151
ZMQ_CONNECT_TIMEOUT: Set connect() timeout
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets 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.


152 153 154 155
ZMQ_CURVE_PUBLICKEY: Set CURVE public key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the socket's long term public key. You must set this on CURVE client
sockets, see linkzmq:zmq_curve[7]. You can provide the key as 32 binary
156 157 158
bytes, or as a 40-character string encoded in the Z85 encoding format and
terminated in a null byte. The public key must always be used with the
matching secret key. To generate a public/secret key pair, use
159 160
linkzmq:zmq_curve_keypair[3]. To derive the public key from a secret key,
use linkzmq:zmq_curve_public[3].
161 162 163

NOTE: an option value size of 40 is supported for backwards compatibility,
though is deprecated.
Martin Lucina's avatar
Martin Lucina committed
164

165
[horizontal]
166
Option value type:: binary data or Z85 text string
167
Option value size:: 32 or 41
168 169 170 171 172 173 174 175 176
Default value:: NULL
Applicable socket types:: all, when using TCP transport


ZMQ_CURVE_SECRETKEY: Set CURVE secret key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the socket's long term secret key. You must set this on both CURVE
client and server sockets, see linkzmq:zmq_curve[7]. You can provide the
key as 32 binary bytes, or as a 40-character string encoded in the Z85
177
encoding format and terminated in a null byte. To generate a public/secret
178 179
key pair, use linkzmq:zmq_curve_keypair[3]. To derive the public key from
a secret key, use linkzmq:zmq_curve_public[3].
180 181 182

NOTE: an option value size of 40 is supported for backwards compatibility,
though is deprecated.
183 184 185

[horizontal]
Option value type:: binary data or Z85 text string
186
Option value size:: 32 or 41
187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212
Default value:: NULL
Applicable socket types:: all, when using TCP transport


ZMQ_CURVE_SERVER: Set CURVE server role
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Defines whether the socket will act as server for CURVE security, see
linkzmq:zmq_curve[7]. A value of '1' means the socket will act as
CURVE server. A value of '0' means the socket will not act as CURVE
server, and its security role then depends on other option settings.
Setting this to '0' shall reset the socket security to NULL. When you
set this you must also set the server's secret key using the
ZMQ_CURVE_SECRETKEY option. A server socket does not need to know
its own public key.

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


ZMQ_CURVE_SERVERKEY: Set CURVE server key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the socket's long term server key. You must set this on CURVE client
sockets, see linkzmq:zmq_curve[7]. You can provide the key as 32 binary
213 214 215 216 217 218 219
bytes, or as a 40-character string encoded in the Z85 encoding format and
terminated in a null byte. This key must have been generated together with
the server's secret key. To generate a public/secret key pair, use
linkzmq:zmq_curve_keypair[3].

NOTE: an option value size of 40 is supported for backwards compatibility,
though is deprecated.
220 221 222

[horizontal]
Option value type:: binary data or Z85 text string
223
Option value size:: 32 or 41
224 225
Default value:: NULL
Applicable socket types:: all, when using TCP transport
Martin Lucina's avatar
Martin Lucina committed
226 227


228 229
ZMQ_GSSAPI_PLAINTEXT: Disable GSSAPI encryption
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Patrik Wenger's avatar
Patrik Wenger committed
230
Defines whether communications on the socket will be encrypted, see
231 232 233 234 235 236 237 238 239 240 241 242
linkzmq:zmq_gssapi[7]. 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 transport


ZMQ_GSSAPI_PRINCIPAL: Set name of GSSAPI principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
J.T. Conklin's avatar
J.T. Conklin committed
243
Sets the name of the principal for whom GSSAPI credentials should be acquired.
244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266

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


ZMQ_GSSAPI_SERVER: Set GSSAPI server role
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Defines whether the socket will act as server for GSSAPI security, see
linkzmq:zmq_gssapi[7]. A value of '1' means the socket will act as GSSAPI
server. A value of '0' means the socket will act as GSSAPI client.

[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0 (false)
Applicable socket types:: all, when using TCP transport


ZMQ_GSSAPI_SERVICE_PRINCIPAL: Set name of GSSAPI service principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
J.T. Conklin's avatar
J.T. Conklin committed
267
Sets the name of the principal of the GSSAPI server to which a GSSAPI client
268 269 270 271 272 273 274 275
intends to connect.

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

276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304
ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Set name type of service principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the name type of the GSSAPI service principal.  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 transport

ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Set name type of principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the name type of the GSSAPI principal.  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 transport
305

306 307 308 309
ZMQ_HANDSHAKE_IVL: Set maximum handshake interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_HANDSHAKE_IVL' option shall set the maximum handshake interval for
the specified 'socket'. Handshaking is the exchange of socket configuration
310
information (socket type, routing id, security) that occurs when a connection
311 312 313 314 315 316 317 318 319 320
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

321

322 323 324 325 326 327 328 329 330 331 332 333
ZMQ_HEARTBEAT_IVL: Set interval between sending ZMTP heartbeats
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_HEARTBEAT_IVL' option shall set the interval between sending ZMTP heartbeats
for the specified 'socket'. If this option is set and is greater than 0, then a 'PING'
ZMTP command will be sent every 'ZMQ_HEARTBEAT_IVL' milliseconds.

[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0
Applicable socket types:: all, when using connection-oriented transports

334

335 336 337 338 339 340 341 342 343 344 345 346
ZMQ_HEARTBEAT_TIMEOUT: Set timeout for ZMTP heartbeats
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_HEARTBEAT_TIMEOUT' option shall set how long to wait before timing-out a
connection after sending a 'PING' ZMTP command and not receiving any traffic. This
option is only valid if 'ZMQ_HEARTBEAT_IVL' is also set, and is greater than 0. The
connection will time out if there is no traffic received after sending the 'PING'
command, but the received traffic does not have to be a 'PONG' command - any received
traffic will cancel the timeout.

[horizontal]
Option value type:: int
Option value unit:: milliseconds
347
Default value:: 0 normally, ZMQ_HEARTBEAT_IVL if it is set
348 349
Applicable socket types:: all, when using connection-oriented transports

350

351 352 353 354 355
ZMQ_HEARTBEAT_TTL: Set the TTL value for ZMTP heartbeats
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_HEARTBEAT_TTL' option shall set the timeout on the remote peer for ZMTP
heartbeats. If this option is greater than 0, the remote side shall time out the
connection if it does not receive any more traffic within the TTL period. This option
356 357 358
does not have any effect if 'ZMQ_HEARTBEAT_IVL' is not set or is 0. Internally, this
value is rounded down to the nearest decisecond, any value less than 100 will have
no effect.
359 360

[horizontal]
361 362
Option value type:: int
Option value unit:: milliseconds
363
Default value:: 0
364
Maximum value:: 6553599 (which is 2^16-1 deciseconds)
365
Applicable socket types:: all, when using connection-oriented transports
366

367

368 369
ZMQ_IDENTITY: Set socket identity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
370 371
This option name is now deprecated. Use ZMQ_ROUTING_ID instead. 
ZMQ_IDENTITY remains as an alias for now. 
372 373


374 375 376 377 378 379 380 381
ZMQ_IMMEDIATE: Queue messages only to completed connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
By default queues will fill on outgoing connections even if the connection has
not completed. This can lead to "lost" messages on sockets with round-robin
routing (REQ, PUSH, DEALER). If this option is set to `1`, messages shall be
queued only to completed connections. 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
382

383
[horizontal]
384
Option value type:: int
385 386 387
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, only for connection-oriented transports.
Martin Lucina's avatar
Martin Lucina committed
388 389


390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411
ZMQ_INVERT_MATCHING: Invert message filtering
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reverses the filtering behavior of PUB-SUB sockets, when set to 1.

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


412 413 414 415 416 417
ZMQ_IPV6: Enable IPv6 on socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Set 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
418

419
[horizontal]
420
Option value type:: int
421 422 423
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, when using TCP transports.
424

425

426 427
ZMQ_LINGER: Set linger period for socket shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
428 429
The 'ZMQ_LINGER' option shall set the linger period for the specified 'socket'.
The linger period determines how long pending messages which have yet to be
430 431
sent to a peer shall linger in memory after a socket is disconnected with
linkzmq:zmq_disconnect[3] or closed with linkzmq:zmq_close[3], and further
432 433
affects the termination of the socket's context with linkzmq:zmq_ctx_term[3].
The following outlines the different behaviours:
434

435
* A value of '-1' specifies an infinite linger period. Pending
436
  messages shall not be discarded after a call to _zmq_disconnect()_ or
437
  _zmq_close()_; attempting to terminate the socket's context with _zmq_ctx_term()_
438
  shall block until all pending messages have been sent to a peer.
439 440

* The value of '0' specifies no linger period. Pending messages shall be
441
  discarded immediately after a call to _zmq_disconnect()_ or _zmq_close()_.
442 443

* Positive values specify an upper bound for the linger period in milliseconds.
444
  Pending messages shall not be discarded after a call to _zmq_disconnect()_ or
445
  _zmq_close()_; attempting to terminate the socket's context with _zmq_ctx_term()_
446 447
  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.
448 449 450 451

[horizontal]
Option value type:: int
Option value unit:: milliseconds
452
Default value:: -1 (infinite)
453 454 455
Applicable socket types:: all


456 457 458 459 460 461 462 463 464 465
ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Limits the size of the inbound message. If a peer sends a message larger than
ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means 'no limit'.

[horizontal]
Option value type:: int64_t
Option value unit:: bytes
Default value:: -1
Applicable socket types:: all
466

467

468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487
ZMQ_METADATA: Add application metadata properties to a socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The _ZMQ_METADATA_ option shall add application metadata to the specified _socket_,
the metadata is exchanged with peers during connection setup. A metadata property is
specfied as a string, delimited by a colon, starting with the metadata _property_
followed by the metadata value, for example "X-key:value".
_Property_ names are restrited to maximum 255 characters and must be prefixed by "X-".
Multiple application metadata properties can be added to a socket by executing zmq_setsockopt()
multiple times. As the argument is a null-terminated string, binary data must be encoded
before it is added e.g. using Z85 (linkzmq:zmq_z85_encode[3]).

NOTE: in DRAFT state, not yet available in stable releases.

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


488 489 490 491 492
ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the time-to-live field in every multicast packet sent from this socket.
The default is 1 which means that the multicast packets don't leave the local
network.
493 494 495

[horizontal]
Option value type:: int
496 497 498
Option value unit:: network hops
Default value:: 1
Applicable socket types:: all, when using multicast transports
499 500


501 502 503 504 505 506 507 508 509 510 511 512 513 514 515
ZMQ_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast packets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets 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


516 517 518 519 520 521
ZMQ_PLAIN_PASSWORD: Set PLAIN security password
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the password for outgoing connections over TCP or IPC. If you set this
to a non-null value, the security mechanism used for connections shall be
PLAIN, see linkzmq:zmq_plain[7]. If you set this to a null value, the security
mechanism used for connections shall be NULL, see linkzmq:zmq_null[3].
522

523 524 525 526 527 528 529 530 531 532 533 534 535 536
[horizontal]
Option value type:: character string
Option value unit:: N/A
Default value:: not set
Applicable socket types:: all, when using TCP transport


ZMQ_PLAIN_SERVER: Set PLAIN server role
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Defines whether the socket will act as server for PLAIN security, see
linkzmq:zmq_plain[7]. A value of '1' means the socket will act as
PLAIN server. A value of '0' means the socket will not act as PLAIN
server, and its security role then depends on other option settings.
Setting this to '0' shall reset the socket security to NULL.
537 538 539

[horizontal]
Option value type:: int
540 541 542
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: all, when using TCP transport
543 544


545 546 547 548 549 550 551 552 553 554 555 556 557 558
ZMQ_PLAIN_USERNAME: Set PLAIN security username
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the username for outgoing connections over TCP or IPC. If you set this
to a non-null value, the security mechanism used for connections shall be
PLAIN, see linkzmq:zmq_plain[7]. If you set this to a null value, the security
mechanism used for connections shall be NULL, see linkzmq:zmq_null[3].

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


559
ZMQ_USE_FD: Set the pre-allocated socket file descriptor
560
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580
When set to a positive integer value before zmq_bind is called on the socket,
the socket shall use the corresponding file descriptor for connections over
TCP or IPC instead of allocating a new file descriptor.
Useful for writing systemd socket activated services. If set to -1 (default),
a new file descriptor will be allocated instead (default behaviour).

NOTE: if set after calling zmq_bind, this option shall have no effect.
NOTE: the file descriptor passed through MUST have been ran through the "bind"
      and "listen" system calls beforehand. Also, socket option that would
      normally be passed through zmq_setsockopt like TCP buffers length,
      IP_TOS or SO_REUSEADDR MUST be set beforehand by the caller, as they
      must be set before the socket is bound.

[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


581 582 583 584 585 586 587 588 589 590
ZMQ_PROBE_ROUTER: bootstrap connections to ROUTER sockets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When set to 1, the socket will automatically send an empty message when a
new connection is made or accepted. You may set this on REQ, DEALER, or
ROUTER sockets connected to a ROUTER socket. The application must filter
such empty messages. The ZMQ_PROBE_ROUTER option in effect provides the
ROUTER application with an event signaling the arrival of a new peer.

NOTE: do not set this option on a socket that talks to any other socket
types: the results are undefined.
591 592 593

[horizontal]
Option value type:: int
594 595 596
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: ZMQ_ROUTER, ZMQ_DEALER, ZMQ_REQ
597

598

599 600 601 602 603 604 605 606 607 608
ZMQ_RATE: Set multicast data rate
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RATE' option shall set the maximum send or receive data rate for
multicast transports such as linkzmq:zmq_pgm[7] 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
609

610 611 612 613

ZMQ_RCVBUF: Set kernel receive buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVBUF' option shall set the underlying kernel receive buffer size for
614
the 'socket' to the specified size in bytes.  A value of -1 means leave the
615 616
OS default unchanged. For details refer to your operating system documentation
for the 'SO_RCVBUF' socket option.
617 618

[horizontal]
619
Option value type:: int
620
Option value unit:: bytes
621
Default value:: -1
622 623
Applicable socket types:: all

624

625 626 627 628 629 630 631
ZMQ_RCVHWM: Set high water mark for inbound messages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVHWM' option shall set 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.
632

633 634 635 636 637
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.
638 639 640

[horizontal]
Option value type:: int
641 642 643
Option value unit:: messages
Default value:: 1000
Applicable socket types:: all
644

645

646 647 648 649 650 651 652 653 654 655 656 657 658 659 660
ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the timeout for receive operation on the socket. If the value is `0`,
_zmq_recv(3)_ will return immediately, with a EAGAIN error if there is no
message to receive. If the value is `-1`, it will block until a message is
available. For all other values, it will wait for a message for that amount
of time before returning with an EAGAIN error.

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


661 662 663 664 665 666
ZMQ_RECONNECT_IVL: Set reconnection interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECONNECT_IVL' option shall set 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.
667

668 669
NOTE: The reconnection interval may be randomized by 0MQ to prevent
reconnection storms in topologies with a large number of peers per socket.
670 671 672 673

[horizontal]
Option value type:: int
Option value unit:: milliseconds
674 675
Default value:: 100
Applicable socket types:: all, only for connection-oriented transports
676 677


678 679 680 681 682 683 684 685
ZMQ_RECONNECT_IVL_MAX: Set maximum reconnection interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECONNECT_IVL_MAX' option shall set 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.
Steven McCoy's avatar
Steven McCoy committed
686

687
NOTE:  Values less than ZMQ_RECONNECT_IVL will be ignored.
Pieter Hintjens's avatar
Pieter Hintjens committed
688 689 690

[horizontal]
Option value type:: int
691 692 693
Option value unit:: milliseconds
Default value:: 0 (only use ZMQ_RECONNECT_IVL)
Applicable socket types:: all, only for connection-oriented transports
Pieter Hintjens's avatar
Pieter Hintjens committed
694 695


696 697 698 699 700 701
ZMQ_RECOVERY_IVL: Set multicast recovery interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECOVERY_IVL' option shall set 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.
Pieter Hintjens's avatar
Pieter Hintjens committed
702

703 704 705
CAUTION: Exercise care when setting large recovery intervals as the data
needed for recovery will be held in memory. For example, a 1 minute recovery
interval at a data rate of 1Gbps requires a 7GB in-memory buffer.
Steven McCoy's avatar
Steven McCoy committed
706 707 708

[horizontal]
Option value type:: int
709 710 711
Option value unit:: milliseconds
Default value:: 10000
Applicable socket types:: all, when using multicast transports
Steven McCoy's avatar
Steven McCoy committed
712 713


714 715
ZMQ_REQ_CORRELATE: match replies with requests
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
716
The default behaviour of REQ sockets is to rely on the ordering of messages to
717 718 719 720 721
match requests and responses and that is usually sufficient. When this option
is set to 1, the REQ socket will prefix outgoing messages with an extra frame
containing a request id. That means the full message is (request id, 0,
user frames...). The REQ socket will discard all incoming messages that don't
begin with these two frames.
722 723 724

[horizontal]
Option value type:: int
725
Option value unit:: 0, 1
726
Default value:: 0
727
Applicable socket types:: ZMQ_REQ
728 729


730 731 732 733
ZMQ_REQ_RELAXED: relax strict alternation between request and reply
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
By default, a REQ socket does not allow initiating a new request with
_zmq_send(3)_ until the reply to the previous one has been received.
734 735 736
When set to 1, sending another message is allowed and previous replies will
be discarded if any. The request-reply state machine is reset and a new
request is sent to the next available peer.
737

738 739 740
If set to 1, also enable ZMQ_REQ_CORRELATE to ensure correct matching of
requests and replies. Otherwise a late reply to an aborted request can be
reported as the reply to the superseding request.
741 742 743

[horizontal]
Option value type:: int
744 745 746
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: ZMQ_REQ
747

748

749 750 751
ZMQ_ROUTER_HANDOVER: handle duplicate client routing ids on ROUTER sockets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If two clients use the same routing id when connecting to a ROUTER, the
Pieter Hintjens's avatar
Pieter Hintjens committed
752 753
results shall depend on the ZMQ_ROUTER_HANDOVER option setting. If that
is not set (or set to the default of zero), the ROUTER socket shall reject
754
clients trying to connect with an already-used routing id. If that option
Pieter Hintjens's avatar
Pieter Hintjens committed
755 756
is set to 1, the ROUTER socket shall hand-over the connection to the new
client and disconnect the existing one.
757

Pieter Hintjens's avatar
Pieter Hintjens committed
758
[horizontal]
759 760 761 762 763
Option value type:: int
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: ZMQ_ROUTER

764

765 766
ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER sockets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
767
Sets the ROUTER socket behaviour when an unroutable message is encountered. A
768
value of `0` is the default and discards the message silently when it cannot be
769 770 771 772 773
routed or the peers SNDHWM is reached.  A value of `1` returns an
'EHOSTUNREACH' error code if the message cannot be routed or 'EAGAIN' error
code if the SNDHWM is reached and ZMQ_DONTWAIT was used. Without ZMQ_DONTWAIT
it will block until the SNDTIMEO is reached or a spot in the send queue opens
up.
774

775 776 777
When ZMQ_ROUTER_MANDATORY is set to `1`, 'ZMQ_POLLOUT' events will be generated
if one or more messages can be sent to at least one of the peers. If
ZMQ_ROUTER_MANDATORY is set to `0`, the socket will generate a 'ZMQ_POLLOUT'
778
event on every call to 'zmq_poll' resp. 'zmq_poller_wait_all'.
779

Kobolog's avatar
Kobolog committed
780 781
[horizontal]
Option value type:: int
782 783
Option value unit:: 0, 1
Default value:: 0
Kobolog's avatar
Kobolog committed
784 785 786
Applicable socket types:: ZMQ_ROUTER


787 788
ZMQ_ROUTER_RAW: switch ROUTER socket to raw mode
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Pieter Hintjens's avatar
Pieter Hintjens committed
789
Sets the raw mode on the ROUTER, when set to 1. When the ROUTER socket is in
790 791
raw mode, and when using the tcp:// transport, it will read and write TCP data
without 0MQ framing. This lets 0MQ applications talk to non-0MQ applications.
792
When using raw mode, you cannot set explicit identities, and the ZMQ_SNDMORE
793
flag is ignored when sending data messages. In raw mode you can close a specific
794
connection by sending it a zero-length message (following the routing id frame).
795

796 797
NOTE: This option is deprecated, please use ZMQ_STREAM sockets instead.

798 799 800 801 802 803 804
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: ZMQ_ROUTER


805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826
ZMQ_ROUTING_ID: Set socket routing id
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_ROUTING_ID' option shall set the routing id of the specified 'socket'
when connecting to a ROUTER socket. 

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.

If two clients use the same routing id when connecting to a ROUTER, the
results shall depend on the ZMQ_ROUTER_HANDOVER option setting. If that
is not set (or set to the default of zero), the ROUTER socket shall reject
clients trying to connect with an already-used routing id. If that option
is set to 1, the ROUTER socket shall hand-over the connection to the new
client and disconnect the existing one.

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


827 828 829
ZMQ_SNDBUF: Set kernel transmit buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SNDBUF' option shall set the underlying kernel transmit buffer size
830
for the 'socket' to the specified size in bytes.  A value of -1 means leave
831 832
the OS default unchanged. For details please refer to your operating system
documentation for the 'SO_SNDBUF' socket option.
833 834 835

[horizontal]
Option value type:: int
836
Option value unit:: bytes
837
Default value:: -1
838
Applicable socket types:: all
839 840


841 842 843 844 845 846 847
ZMQ_SNDHWM: Set high water mark for outbound messages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SNDHWM' option shall set 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.
848

849 850 851 852 853
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.
854

855
NOTE: 0MQ does not guarantee that the socket will accept as many as ZMQ_SNDHWM
856
messages, and the actual limit may be as much as 90% lower depending on the
857
flow of messages on the socket.
858 859 860

[horizontal]
Option value type:: int
861 862 863
Option value unit:: messages
Default value:: 1000
Applicable socket types:: all
864

865

866 867 868 869 870 871 872
ZMQ_SNDTIMEO: Maximum time before a send operation returns with EAGAIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets 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.
873 874 875

[horizontal]
Option value type:: int
876 877 878
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
879 880


881 882 883 884 885 886 887 888 889 890 891 892 893 894 895
ZMQ_SOCKS_PROXY: Set SOCKS5 proxy address
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the SOCKS5 proxy address that shall be used by the socket for the TCP
connection(s). Does not support SOCKS5 authentication. If the endpoints are
domain names instead of addresses they shall not be resolved and they shall
be forwarded unchanged to the SOCKS proxy service in the client connection
request message (address type 0x03 domain name).

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


896 897 898 899 900
ZMQ_STREAM_NOTIFY: send connect and disconnect notifications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Enables connect and disconnect notifications on a STREAM socket, when set
to 1. When notifications are enabled, the socket delivers a zero-length
message when a peer connects or disconnects.
901 902 903 904

[horizontal]
Option value type:: int
Option value unit:: 0, 1
905
Default value:: 1
906 907 908
Applicable socket types:: ZMQ_STREAM


909 910 911 912 913
ZMQ_SUBSCRIBE: Establish message filter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SUBSCRIBE' option shall establish a new message filter on a 'ZMQ_SUB'
socket. Newly created 'ZMQ_SUB' sockets shall filter out all incoming messages,
therefore you should call this option to establish an initial message filter.
914

915 916 917 918 919
An empty 'option_value' of length zero shall subscribe to all incoming
messages. A non-empty 'option_value' shall subscribe to all messages beginning
with the specified prefix. Multiple filters may be attached to a single
'ZMQ_SUB' socket, in which case a message shall be accepted if it matches at
least one filter.
920 921

[horizontal]
922 923 924 925
Option value type:: binary data
Option value unit:: N/A
Default value:: N/A
Applicable socket types:: ZMQ_SUB
926 927


928 929 930 931
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.
932 933

[horizontal]
934 935 936 937
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.
938 939


940 941 942 943
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.
944 945

[horizontal]
946 947 948 949
Option value type:: int
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
950 951


952
ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
953
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
954
Override 'TCP_KEEPIDLE' (or 'TCP_KEEPALIVE' on some OS) socket option (where
955 956
supported by OS). The default value of `-1` means to skip any overrides and
leave it to OS default.
957 958

[horizontal]
959 960 961 962
Option value type:: int
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
963 964


965
ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option
966
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
967 968
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.
969 970 971

[horizontal]
Option value type:: int
972 973 974
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
975

976

977
ZMQ_TCP_MAXRT: Set TCP Maximum Retransmit Timeout
978
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
979
On OSes where it is supported, sets how long before an unacknowledged TCP
980 981 982 983
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.
984 985 986 987 988 989 990 991

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


992 993 994 995 996
ZMQ_TOS: Set the Type-of-Service on socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the ToS fields (Differentiated services (DS) and Explicit Congestion
Notification (ECN) field of the IP header. The ToS field is typically used
to specify a packets priority. The availability of this option is dependent
J.T. Conklin's avatar
J.T. Conklin committed
997
on intermediate network equipment that inspect the ToS field and provide a
998
path for low-delay, high-throughput, highly-reliable service, etc.
999 1000 1001

[horizontal]
Option value type:: int
1002
Option value unit:: >0
1003
Default value:: 0
1004
Applicable socket types:: all, only for connection-oriented transports
1005 1006


1007 1008 1009 1010 1011 1012 1013
ZMQ_UNSUBSCRIBE: Remove message filter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_UNSUBSCRIBE' option shall remove an existing message filter on a
'ZMQ_SUB' socket. The filter specified must match an existing filter previously
established with the 'ZMQ_SUBSCRIBE' option. If the socket has several
instances of the same filter attached the 'ZMQ_UNSUBSCRIBE' option shall remove
only one instance, leaving the rest in place and functional.
1014 1015

[horizontal]
1016
Option value type:: binary data
1017
Option value unit:: N/A
1018 1019
Default value:: N/A
Applicable socket types:: ZMQ_SUB
1020 1021


1022 1023 1024
ZMQ_XPUB_VERBOSE: pass duplicate subscribe messages on XPUB socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the 'XPUB' socket behaviour on new duplicated subscriptions. If enabled,
1025
the socket passes all subscribe messages to the caller. If disabled,
1026 1027
only the first subscription to each filter will be passed. The default is 0
(disabled).
1028 1029 1030

[horizontal]
Option value type:: int
1031 1032 1033 1034 1035
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: ZMQ_XPUB


1036 1037 1038 1039 1040 1041
ZMQ_XPUB_VERBOSER: pass duplicate subscribe and unsubscribe messages on XPUB socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sets the 'XPUB' socket behaviour on new duplicated subscriptions and
unsubscriptions. If enabled, the socket passes all subscribe and unsubscribe
messages to the caller. If disabled, only the first subscription to each filter and
the last unsubscription from each filter will be passed. The default is 0
1042
(disabled).
1043 1044 1045

[horizontal]
Option value type:: int
1046 1047
Option value unit:: 0, 1
Default value:: 0
1048
Applicable socket types:: ZMQ_XPUB
1049

1050

1051 1052
ZMQ_XPUB_MANUAL: change the subscription handling to manual
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
Sets the 'XPUB' socket subscription handling mode manual/automatic.
A value of '0' is the default and subscription requests will be handled automatically.
A value of '1' will change the subscription requests handling to manual, 
with manual mode subscription requests are not added to the subscription list.
To add subscription the user need to call setsockopt with ZMQ_SUBSCRIBE on XPUB socket.

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

1065

1066 1067
ZMQ_XPUB_NODROP: do not silently drop messages if SENDHWM is reached
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1068
Sets the 'XPUB' socket behaviour to return error EAGAIN if SENDHWM is
1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080
reached and the message could not be send. 

A value of `0` is the default and drops the message silently when the peers
SNDHWM is reached.  A value of `1` returns an 'EAGAIN' error code if the
SNDHWM is reached and ZMQ_DONTWAIT was used.

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

1081

1082 1083
ZMQ_XPUB_WELCOME_MSG: set welcome message that will be received by subscriber when connecting
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095
Sets a welcome message the will be recieved by subscriber when connecting.
Subscriber must subscribe to the Welcome message before connecting.
Welcome message will also be sent on reconnecting.
For welcome message to work well user must poll on incoming subscription messages on the XPUB socket and handle them.

Use NULL and lenght of zero to disable welcome message.

[horizontal]
Option value type:: binary data
Option value unit:: N/A
Default value:: NULL
Applicable socket types:: ZMQ_XPUB
1096

1097

1098 1099
ZMQ_ZAP_DOMAIN: Set RFC 27 authentication domain
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1100 1101
Sets the domain for ZAP (ZMQ RFC 27) authentication. A ZAP domain must be 
specified to enable authentication. When the ZAP domain is empty, which is 
1102 1103 1104
the default, ZAP authentication is disabled. This is not compatible with
previous versions of libzmq, so it can be controlled by ZMQ_ZAP_ENFORCE_DOMAIN
which for now is disabled by default.
1105
See http://rfc.zeromq.org/spec:27 for more details.
1106 1107 1108 1109

[horizontal]
Option value type:: character string
Option value unit:: N/A
1110
Default value:: empty
1111 1112 1113
Applicable socket types:: all, when using TCP transport


1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
ZMQ_ZAP_ENFORCE_DOMAIN: Set ZAP domain handling to strictly adhere the RFC
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ZAP (ZMQ RFC 27) authentication protocol specifies that a domain must
always be set. Older versions of libzmq did not follow the spec and allowed
an empty domain to be set.
This option can be used to enabled or disable the stricter, backward
incompatible behaviour. For now it is disabled by default, but in a future
version it will be enabled by default.

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


1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227
ZMQ_TCP_ACCEPT_FILTER: Assign filters to allow new TCP connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assign an arbitrary number of filters that will be applied for each new TCP
transport connection on a listening socket. If no filters are applied, then
the TCP transport allows connections from any IP address. If at least one
filter is applied then new connection source ip should be matched. To clear
all filters call zmq_setsockopt(socket, ZMQ_TCP_ACCEPT_FILTER, NULL, 0).
Filter is a null-terminated string with ipv6 or ipv4 CIDR.

NOTE: This option is deprecated, please use authentication via the ZAP API
and IP address whitelisting / blacklisting.

[horizontal]
Option value type:: binary data
Option value unit:: N/A
Default value:: no filters (allow from all)
Applicable socket types:: all listening sockets, when using TCP transports.


ZMQ_IPC_FILTER_GID: Assign group ID filters to allow new IPC connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied, then
the IPC transport allows connections from any process. If at least one UID,
GID, or PID filter is applied then new connection credentials should be
matched. To clear all GID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_GID, NULL, 0).

NOTE: GID filters are only available on platforms supporting SO_PEERCRED or
LOCAL_PEERCRED socket options (currently only Linux and later versions of
OS X).

NOTE: This option is deprecated, please use authentication via the ZAP API
and IPC whitelisting / blacklisting.

[horizontal]
Option value type:: gid_t
Option value unit:: N/A
Default value:: no filters (allow from all)
Applicable socket types:: all listening sockets, when using IPC transports.


ZMQ_IPC_FILTER_PID: Assign process ID filters to allow new IPC connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied, then
the IPC transport allows connections from any process. If at least one UID,
GID, or PID filter is applied then new connection credentials should be
matched. To clear all PID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_PID, NULL, 0).

NOTE: PID filters are only available on platforms supporting the SO_PEERCRED
socket option (currently only Linux).

NOTE: This option is deprecated, please use authentication via the ZAP API
and IPC whitelisting / blacklisting.

[horizontal]
Option value type:: pid_t
Option value unit:: N/A
Default value:: no filters (allow from all)
Applicable socket types:: all listening sockets, when using IPC transports.


ZMQ_IPC_FILTER_UID: Assign user ID filters to allow new IPC connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assign an arbitrary number of filters that will be applied for each new IPC
transport connection on a listening socket. If no IPC filters are applied, then
the IPC transport allows connections from any process. If at least one UID,
GID, or PID filter is applied then new connection credentials should be
matched. To clear all UID filters call zmq_setsockopt(socket,
ZMQ_IPC_FILTER_UID, NULL, 0).

NOTE: UID filters are only available on platforms supporting SO_PEERCRED or
LOCAL_PEERCRED socket options (currently only Linux and later versions of
OS X).

NOTE: This option is deprecated, please use authentication via the ZAP API
and IPC whitelisting / blacklisting.

[horizontal]
Option value type:: uid_t
Option value unit:: N/A
Default value:: no filters (allow from all)
Applicable socket types:: all listening sockets, when using IPC transports.


ZMQ_IPV4ONLY: Use IPv4-only on socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Set the IPv4-only option for the socket. This option is deprecated.
Please use the ZMQ_IPV6 option.

[horizontal]
Option value type:: int
Option value unit:: boolean
Default value:: 1 (true)
Applicable socket types:: all, when using TCP transports.

1228

Ilya Kulakov's avatar
Ilya Kulakov committed
1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276
ZMQ_VMCI_BUFFER_SIZE: Set buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_SIZE` option shall set 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: Set min buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_MIN_SIZE` option shall set 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: Set max buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_MAX_SIZE` option shall set 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: Set connection timeout of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_CONNECT_TIMEOUT` option shall set 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


1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287
ZMQ_MULTICAST_LOOP: Control multicast local loopback
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For multicast UDP sender sockets this option sets whether the data
sent should be looped back on local listening sockets.

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

1288 1289
RETURN VALUE
------------
Martin Lucina's avatar
Martin Lucina committed
1290
The _zmq_setsockopt()_ function shall return zero if successful. Otherwise it
Martin Lucina's avatar
Martin Lucina committed
1291
shall return `-1` and set 'errno' to one of the values defined below.
1292 1293 1294 1295

ERRORS
------
*EINVAL*::
Martin Lucina's avatar
Martin Lucina committed
1296 1297
The requested option _option_name_ is unknown, or the requested _option_len_ or
_option_value_ is invalid.
1298
*ETERM*::
Martin Lucina's avatar
Martin Lucina committed
1299
The 0MQ 'context' associated with the specified 'socket' was terminated.
1300 1301
*ENOTSOCK*::
The provided 'socket' was invalid.
1302 1303
*EINTR*::
The operation was interrupted by delivery of a signal.
1304

1305 1306 1307

EXAMPLE
-------
Martin Lucina's avatar
Martin Lucina committed
1308
.Subscribing to messages on a 'ZMQ_SUB' socket
1309
----
Martin Lucina's avatar
Martin Lucina committed
1310 1311
/* Subscribe to all messages */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "", 0);
1312
assert (rc == 0);
Martin Lucina's avatar
Martin Lucina committed
1313 1314 1315 1316 1317 1318
/* Subscribe to messages prefixed with "ANIMALS.CATS" */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "ANIMALS.CATS", 12);
----

.Setting I/O thread affinity
----
Martin Lucina's avatar
Martin Lucina committed
1319
int64_t affinity;
Martin Lucina's avatar
Martin Lucina committed
1320
/* Incoming connections on TCP port 5555 shall be handled by I/O thread 1 */
Martin Lucina's avatar
Martin Lucina committed
1321
affinity = 1;
1322
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof (affinity));
Martin Lucina's avatar
Martin Lucina committed
1323 1324 1325 1326
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5555");
assert (rc);
/* Incoming connections on TCP port 5556 shall be handled by I/O thread 2 */
Martin Lucina's avatar
Martin Lucina committed
1327
affinity = 2;
1328
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof (affinity));
Martin Lucina's avatar
Martin Lucina committed
1329
assert (rc);
1330
rc = zmq_bind (socket, "tcp://lo:5556");
Martin Lucina's avatar
Martin Lucina committed
1331
assert (rc);
1332 1333 1334 1335 1336
----


SEE ALSO
--------
Martin Lucina's avatar
Martin Lucina committed
1337
linkzmq:zmq_getsockopt[3]
1338
linkzmq:zmq_socket[3]
1339 1340
linkzmq:zmq_plain[7]
linkzmq:zmq_curve[7]
1341 1342
linkzmq:zmq[7]

1343

1344 1345
AUTHORS
-------
1346 1347
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>.