1ZMQ_GETSOCKOPT(3)                 0MQ Manual                 ZMQ_GETSOCKOPT(3)
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NAME

6       zmq_getsockopt - get 0MQ socket options
7

SYNOPSIS

9       int zmq_getsockopt (void *socket, int option_name, void *option_value,
10       size_t *option_len);
11

DESCRIPTION

13       The zmq_getsockopt() function shall retrieve the value for the option
14       specified by the option_name argument for the 0MQ socket pointed to by
15       the socket argument, and store it in the buffer pointed to by the
16       option_value argument. The option_len argument is the size in bytes of
17       the buffer pointed to by option_value; upon successful completion
18       zmq_getsockopt() shall modify the option_len argument to indicate the
19       actual size of the option value stored in the buffer.
20
21       The following options can be retrieved with the zmq_getsockopt()
22       function:
23
24   ZMQ_AFFINITY: Retrieve I/O thread affinity
25       The ZMQ_AFFINITY option shall retrieve the I/O thread affinity for
26       newly created connections on the specified socket.
27
28       Affinity determines which threads from the 0MQ I/O thread pool
29       associated with the socket’s context shall handle newly created
30       connections. A value of zero specifies no affinity, meaning that work
31       shall be distributed fairly among all 0MQ I/O threads in the thread
32       pool. For non-zero values, the lowest bit corresponds to thread 1,
33       second lowest bit to thread 2 and so on. For example, a value of 3
34       specifies that subsequent connections on socket shall be handled
35       exclusively by I/O threads 1 and 2.
36
37       See also zmq_init(3) for details on allocating the number of I/O
38       threads for a specific context.
39
40
41       Option value type         uint64_t
42
43       Option value unit         N/A (bitmap)
44
45       Default value             0
46
47       Applicable socket types   N/A
48
49
50   ZMQ_BACKLOG: Retrieve maximum length of the queue of outstanding
51       connections
52       The ZMQ_BACKLOG option shall retrieve the maximum length of the queue
53       of outstanding peer connections for the specified socket; this only
54       applies to connection-oriented transports. For details refer to your
55       operating system documentation for the listen function.
56
57
58       Option value type         int
59
60       Option value unit         connections
61
62       Default value             100
63
64
65
66
67
68       Applicable socket types   all, only for
69                                 connection-oriented
70                                 transports
71
72
73   ZMQ_BINDTODEVICE: Retrieve name of device the socket is bound to
74       The ZMQ_BINDTODEVICE option retrieves the name of the device this
75       socket is bound to, eg. an interface or VRF. If a socket is bound to an
76       interface, only packets received from that interface are processed by
77       the socket. If device is a VRF device, then subsequent binds/connects
78       to that socket use addresses in the VRF routing table.
79
80
81       Option value type         character string
82
83       Option value unit         N/A
84
85       Default value             not set
86
87       Applicable socket types   all, when using TCP or UDP
88                                 transports.
89
90
91   ZMQ_CONNECT_TIMEOUT: Retrieve connect() timeout
92       Retrieves how long to wait before timing-out a connect() system call.
93       The connect() system call normally takes a long time before it returns
94       a time out error. Setting this option allows the library to time out
95       the call at an earlier interval.
96
97
98       Option value type         int
99
100       Option value unit         milliseconds
101
102       Default value             0 (disabled)
103
104       Applicable socket types   all, when using TCP
105                                 transports.
106
107
108   ZMQ_CURVE_PUBLICKEY: Retrieve current CURVE public key
109       Retrieves the current long term public key for the socket. You can
110       provide either a 32 byte buffer, to retrieve the binary key value, or a
111       41 byte buffer, to retrieve the key in a printable Z85 format. NOTE: to
112       fetch a printable key, the buffer must be 41 bytes large to hold the
113       40-char key value and one null byte.
114
115
116       Option value type         binary data or Z85 text
117                                 string
118
119       Option value size         32 or 41
120
121       Default value             null
122
123       Applicable socket types   all, when using TCP
124                                 transport
125
126
127   ZMQ_CURVE_SECRETKEY: Retrieve current CURVE secret key
128       Retrieves the current long term secret key for the socket. You can
129       provide either a 32 byte buffer, to retrieve the binary key value, or a
130       41 byte buffer, to retrieve the key in a printable Z85 format. NOTE: to
131       fetch a printable key, the buffer must be 41 bytes large to hold the
132       40-char key value and one null byte.
133
134
135       Option value type         binary data or Z85 text
136                                 string
137
138       Option value size         32 or 41
139
140       Default value             null
141
142       Applicable socket types   all, when using TCP
143                                 transport
144
145
146   ZMQ_CURVE_SERVERKEY: Retrieve current CURVE server key
147       Retrieves the current server key for the client socket. You can provide
148       either a 32 byte buffer, to retrieve the binary key value, or a 41-byte
149       buffer, to retrieve the key in a printable Z85 format. NOTE: to fetch a
150       printable key, the buffer must be 41 bytes large to hold the 40-char
151       key value and one null byte.
152
153
154       Option value type         binary data or Z85 text
155                                 string
156
157       Option value size         32 or 41
158
159       Default value             null
160
161       Applicable socket types   all, when using TCP
162                                 transport
163
164
165   ZMQ_EVENTS: Retrieve socket event state
166       The ZMQ_EVENTS option shall retrieve the event state for the specified
167       socket. The returned value is a bit mask constructed by OR’ing a
168       combination of the following event flags:
169
170       ZMQ_POLLIN
171           Indicates that at least one message may be received from the
172           specified socket without blocking.
173
174       ZMQ_POLLOUT
175           Indicates that at least one message may be sent to the specified
176           socket without blocking.
177
178       The combination of a file descriptor returned by the ZMQ_FD option
179       being ready for reading but no actual events returned by a subsequent
180       retrieval of the ZMQ_EVENTS option is valid; applications should simply
181       ignore this case and restart their polling operation/event loop.
182
183
184       Option value type         int
185
186       Option value unit         N/A (flags)
187
188       Default value             N/A
189
190       Applicable socket types   all
191
192
193   ZMQ_FD: Retrieve file descriptor associated with the socket
194       The ZMQ_FD option shall retrieve the file descriptor associated with
195       the specified socket. The returned file descriptor can be used to
196       integrate the socket into an existing event loop; the 0MQ library shall
197       signal any pending events on the socket in an edge-triggered fashion by
198       making the file descriptor become ready for reading.
199
200           Note
201           The ability to read from the returned file descriptor does not
202           necessarily indicate that messages are available to be read from,
203           or can be written to, the underlying socket; applications must
204           retrieve the actual event state with a subsequent retrieval of the
205           ZMQ_EVENTS option.
206
207           Note
208           The returned file descriptor is also used internally by the
209           zmq_send and zmq_recv functions. As the descriptor is edge
210           triggered, applications must update the state of ZMQ_EVENTS after
211           each invocation of zmq_send or zmq_recv.To be more explicit: after
212           calling zmq_send the socket may become readable (and vice versa)
213           without triggering a read event on the file descriptor.
214
215           Caution
216           The returned file descriptor is intended for use with a poll or
217           similar system call only. Applications must never attempt to read
218           or write data to it directly, neither should they try to close it.
219
220
221       Option value type         int on POSIX systems,
222                                 SOCKET on Windows
223
224       Option value unit         N/A
225
226       Default value             N/A
227
228       Applicable socket types   all
229
230
231   ZMQ_GSSAPI_PLAINTEXT: Retrieve GSSAPI plaintext or encrypted status
232       Returns the ZMQ_GSSAPI_PLAINTEXT option, if any, previously set on the
233       socket. A value of 1 means that communications will be plaintext. A
234       value of 0 means communications will be encrypted.
235
236
237       Option value type         int
238
239       Option value unit         0, 1
240
241       Default value             0 (false)
242
243       Applicable socket types   all, when using TCP or IPC
244                                 transports
245
246
247   ZMQ_GSSAPI_PRINCIPAL: Retrieve the name of the GSSAPI principal
248       The ZMQ_GSSAPI_PRINCIPAL option shall retrieve the principal name set
249       for the GSSAPI security mechanism. The returned value shall be a
250       NULL-terminated string and MAY be empty. The returned size SHALL
251       include the terminating null byte.
252
253
254       Option value type         NULL-terminated character
255                                 string
256
257       Option value unit         N/A
258
259       Default value             null string
260
261       Applicable socket types   all, when using TCP or IPC
262                                 transports
263
264
265   ZMQ_GSSAPI_SERVER: Retrieve current GSSAPI server role
266       Returns the ZMQ_GSSAPI_SERVER option, if any, previously set on the
267       socket.
268
269
270       Option value type         int
271
272       Option value unit         0, 1
273
274       Default value             0 (false)
275
276       Applicable socket types   all, when using TCP or IPC
277                                 transports
278
279
280   ZMQ_GSSAPI_SERVICE_PRINCIPAL: Retrieve the name of the GSSAPI service
281       principal
282       The ZMQ_GSSAPI_SERVICE_PRINCIPAL option shall retrieve the principal
283       name of the GSSAPI server to which a GSSAPI client socket intends to
284       connect. The returned value shall be a NULL-terminated string and MAY
285       be empty. The returned size SHALL include the terminating null byte.
286
287
288       Option value type         NULL-terminated character
289                                 string
290
291       Option value unit         N/A
292
293       Default value             null string
294
295       Applicable socket types   all, when using TCP or IPC
296                                 transports
297
298
299   ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Retrieve nametype for service
300       principal
301       Returns the ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE option, if any,
302       previously set on the socket. A value of ZMQ_GSSAPI_NT_HOSTBASED (0)
303       means the name specified with ZMQ_GSSAPI_SERVICE_PRINCIPAL is
304       interpreted as a host based name. A value of ZMQ_GSSAPI_NT_USER_NAME
305       (1) means it is interpreted as a local user name. A value of
306       ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2) means it is interpreted as an unparsed
307       principal name string (valid only with the krb5 GSSAPI mechanism).
308
309
310       Option value type         int
311
312       Option value unit         0, 1, 2
313
314       Default value             0
315                                 (ZMQ_GSSAPI_NT_HOSTBASED)
316
317       Applicable socket types   all, when using TCP or IPC
318                                 transports
319
320
321   ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Retrieve nametype for service principal
322       Returns the ZMQ_GSSAPI_PRINCIPAL_NAMETYPE option, if any, previously
323       set on the socket. A value of ZMQ_GSSAPI_NT_HOSTBASED (0) means the
324       name specified with ZMQ_GSSAPI_PRINCIPAL is interpreted as a host based
325       name. A value of ZMQ_GSSAPI_NT_USER_NAME (1) means it is interpreted as
326       a local user name. A value of ZMQ_GSSAPI_NT_KRB5_PRINCIPAL (2) means it
327       is interpreted as an unparsed principal name string (valid only with
328       the krb5 GSSAPI mechanism).
329
330
331
332       Option value type         int
333
334       Option value unit         0, 1, 2
335
336       Default value             0
337                                 (ZMQ_GSSAPI_NT_HOSTBASED)
338
339       Applicable socket types   all, when using TCP or IPC
340                                 transports
341
342
343   ZMQ_HANDSHAKE_IVL: Retrieve maximum handshake interval
344       The ZMQ_HANDSHAKE_IVL option shall retrieve the maximum handshake
345       interval for the specified socket. Handshaking is the exchange of
346       socket configuration information (socket type, routing id, security)
347       that occurs when a connection is first opened, only for
348       connection-oriented transports. If handshaking does not complete within
349       the configured time, the connection shall be closed. The value 0 means
350       no handshake time limit.
351
352
353       Option value type         int
354
355       Option value unit         milliseconds
356
357       Default value             30000
358
359       Applicable socket types   all but ZMQ_STREAM, only
360                                 for connection-oriented
361                                 transports
362
363
364   ZMQ_IDENTITY: Retrieve socket identity
365       This option name is now deprecated. Use ZMQ_ROUTING_ID instead.
366       ZMQ_IDENTITY remains as an alias for now.
367
368   ZMQ_IMMEDIATE: Retrieve attach-on-connect value
369       Retrieve the state of the attach on connect value. If set to 1, will
370       delay the attachment of a pipe on connect until the underlying
371       connection has completed. This will cause the socket to block if there
372       are no other connections, but will prevent queues from filling on pipes
373       awaiting connection.
374
375
376       Option value type         int
377
378       Option value unit         boolean
379
380       Default value             0 (false)
381
382       Applicable socket types   all, primarily when using
383                                 TCP/IPC transports.
384
385
386   ZMQ_INVERT_MATCHING: Retrieve inverted filtering status
387       Returns the value of the ZMQ_INVERT_MATCHING option. A value of 1 means
388       the socket uses inverted prefix matching.
389
390       On PUB and XPUB sockets, this causes messages to be sent to all
391       connected sockets except those subscribed to a prefix that matches the
392       message. On SUB sockets, this causes only incoming messages that do not
393       match any of the socket’s subscriptions to be received by the user.
394
395       Whenever ZMQ_INVERT_MATCHING is set to 1 on a PUB socket, all SUB
396       sockets connecting to it must also have the option set to 1. Failure to
397       do so will have the SUB sockets reject everything the PUB socket sends
398       them. XSUB sockets do not need to do this because they do not filter
399       incoming messages.
400
401
402       Option value type         int
403
404       Option value unit         0,1
405
406       Default value             0
407
408       Applicable socket types   ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB
409
410
411   ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status
412       Retrieve the IPv4-only option for the socket. This option is
413       deprecated. Please use the ZMQ_IPV6 option.
414
415
416       Option value type         int
417
418       Option value unit         boolean
419
420       Default value             1 (true)
421
422       Applicable socket types   all, when using TCP
423                                 transports.
424
425
426   ZMQ_IPV6: Retrieve IPv6 socket status
427       Retrieve the IPv6 option for the socket. A value of 1 means IPv6 is
428       enabled on the socket, while 0 means the socket will use only IPv4.
429       When IPv6 is enabled the socket will connect to, or accept connections
430       from, both IPv4 and IPv6 hosts.
431
432
433       Option value type         int
434
435       Option value unit         boolean
436
437       Default value             0 (false)
438
439       Applicable socket types   all, when using TCP
440                                 transports.
441
442
443   ZMQ_LAST_ENDPOINT: Retrieve the last endpoint set
444       The ZMQ_LAST_ENDPOINT option shall retrieve the last endpoint bound for
445       TCP and IPC transports. The returned value will be a string in the form
446       of a ZMQ DSN. Note that if the TCP host is INADDR_ANY, indicated by a
447       *, then the returned address will be 0.0.0.0 (for IPv4). Note: not
448       supported on GNU/Hurd with IPC due to non-working getsockname().
449
450
451       Option value type         NULL-terminated character
452                                 string
453
454       Option value unit         N/A
455
456       Default value             NULL
457
458       Applicable socket types   all, when binding TCP or
459                                 IPC transports
460
461
462   ZMQ_LINGER: Retrieve linger period for socket shutdown
463       The ZMQ_LINGER option shall retrieve the linger period for the
464       specified socket. The linger period determines how long pending
465       messages which have yet to be sent to a peer shall linger in memory
466       after a socket is closed with zmq_close(3), and further affects the
467       termination of the socket’s context with zmq_ctx_term(3). The following
468       outlines the different behaviours:
469
470       •   The default value of -1 specifies an infinite linger period.
471           Pending messages shall not be discarded after a call to
472           zmq_close(); attempting to terminate the socket’s context with
473           zmq_ctx_term() shall block until all pending messages have been
474           sent to a peer.
475
476       •   The value of 0 specifies no linger period. Pending messages shall
477           be discarded immediately when the socket is closed with
478           zmq_close().
479
480       •   Positive values specify an upper bound for the linger period in
481           milliseconds. Pending messages shall not be discarded after a call
482           to zmq_close(); attempting to terminate the socket’s context with
483           zmq_ctx_term() shall block until either all pending messages have
484           been sent to a peer, or the linger period expires, after which any
485           pending messages shall be discarded.
486
487           Option value type         int
488           Option value unit         milliseconds
489           Default value             -1 (infinite)
490           Applicable socket types   all
491
492
493   ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
494       The option shall retrieve limit for the inbound messages. If a peer
495       sends a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of
496       -1 means no limit.
497
498
499       Option value type         int64_t
500
501       Option value unit         bytes
502
503       Default value             -1
504
505       Applicable socket types   all
506
507
508   ZMQ_MECHANISM: Retrieve current security mechanism
509       The ZMQ_MECHANISM option shall retrieve the current security mechanism
510       for the socket.
511
512
513       Option value type         int
514
515       Option value unit         ZMQ_NULL, ZMQ_PLAIN,
516                                 ZMQ_CURVE, or ZMQ_GSSAPI
517
518       Default value             ZMQ_NULL
519
520       Applicable socket types   all, when using TCP or IPC
521                                 transports
522
523
524   ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
525       The option shall retrieve time-to-live used for outbound multicast
526       packets. The default of 1 means that the multicast packets don’t leave
527       the local network.
528
529
530       Option value type         int
531
532
533
534       Option value unit         network hops
535
536       Default value             1
537
538       Applicable socket types   all, when using multicast
539                                 transports
540
541
542   ZMQ_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast
543       packets
544       The ZMQ_MULTICAST_MAXTPDU option shall retrieve the maximum transport
545       data unit size used for outbound multicast packets.
546
547       This must be set at or below the minimum Maximum Transmission Unit
548       (MTU) for all network paths over which multicast reception is required.
549
550
551       Option value type         int
552
553       Option value unit         bytes
554
555       Default value             1500
556
557       Applicable socket types   all, when using multicast
558                                 transports
559
560
561   ZMQ_PLAIN_PASSWORD: Retrieve current password
562       The ZMQ_PLAIN_PASSWORD option shall retrieve the last password set for
563       the PLAIN security mechanism. The returned value shall be a
564       NULL-terminated string and MAY be empty. The returned size SHALL
565       include the terminating null byte.
566
567
568       Option value type         NULL-terminated character
569                                 string
570
571       Option value unit         N/A
572
573       Default value             null string
574
575       Applicable socket types   all, when using TCP or IPC
576                                 transports
577
578
579   ZMQ_PLAIN_SERVER: Retrieve current PLAIN server role
580       Returns the ZMQ_PLAIN_SERVER option, if any, previously set on the
581       socket.
582
583
584       Option value type         int
585
586       Option value unit         0, 1
587
588       Default value             int
589
590       Applicable socket types   all, when using TCP or IPC
591                                 transports
592
593
594   ZMQ_PLAIN_USERNAME: Retrieve current PLAIN username
595       The ZMQ_PLAIN_USERNAME option shall retrieve the last username set for
596       the PLAIN security mechanism. The returned value shall be a
597       NULL-terminated string and MAY be empty. The returned size SHALL
598       include the terminating null byte.
599
600
601
602       Option value type         NULL-terminated character
603                                 string
604
605       Option value unit         N/A
606
607       Default value             null string
608
609       Applicable socket types   all, when using TCP or IPC
610                                 transports
611
612
613   ZMQ_USE_FD: Retrieve the pre-allocated socket file descriptor
614       The ZMQ_USE_FD option shall retrieve the pre-allocated file descriptor
615       that has been assigned to a ZMQ socket, if any. -1 shall be returned if
616       a pre-allocated file descriptor was not set for the socket.
617
618
619       Option value type         int
620
621       Option value unit         file descriptor
622
623       Default value             -1
624
625       Applicable socket types   all bound sockets, when
626                                 using IPC or TCP transport
627
628
629       ZMQ_PRIORITY: Retrieve the Priority on socket
630
631           Gets the protocol-defined priority for all packets to be sent on this
632           socket, where supported by the OS.
633
634           [horizontal]
635           Option value type:: int
636           Option value unit:: >0
637           Default value:: 0
638           Applicable socket types:: all, only for connection-oriented transports
639
640
641           ZMQ_RATE: Retrieve multicast data rate
642
643       The ZMQ_RATE option shall retrieve the maximum send or receive data
644       rate for multicast transports using the specified socket.
645
646
647       Option value type         int
648
649       Option value unit         kilobits per second
650
651       Default value             100
652
653       Applicable socket types   all, when using multicast
654                                 transports
655
656
657   ZMQ_RCVBUF: Retrieve kernel receive buffer size
658       The ZMQ_RCVBUF option shall retrieve the underlying kernel receive
659       buffer size for the specified socket. For details refer to your
660       operating system documentation for the SO_RCVBUF socket option.
661
662
663       Option value type         int
664
665       Option value unit         bytes
666
667       Default value             8192
668
669
670       Applicable socket types   all
671
672
673   ZMQ_RCVHWM: Retrieve high water mark for inbound messages
674       The ZMQ_RCVHWM option shall return the high water mark for inbound
675       messages on the specified socket. The high water mark is a hard limit
676       on the maximum number of outstanding messages 0MQ shall queue in memory
677       for any single peer that the specified socket is communicating with. A
678       value of zero means no limit.
679
680       If this limit has been reached the socket shall enter an exceptional
681       state and depending on the socket type, 0MQ shall take appropriate
682       action such as blocking or dropping sent messages. Refer to the
683       individual socket descriptions in zmq_socket(3) for details on the
684       exact action taken for each socket type.
685
686
687       Option value type         int
688
689       Option value unit         messages
690
691       Default value             1000
692
693       Applicable socket types   all
694
695
696   ZMQ_RCVMORE: More message data parts to follow
697       The ZMQ_RCVMORE option shall return True (1) if the message part last
698       received from the socket was a data part with more parts to follow. If
699       there are no data parts to follow, this option shall return False (0).
700
701       Refer to zmq_send(3) and zmq_recv(3) for a detailed description of
702       multi-part messages.
703
704
705       Option value type         int
706
707       Option value unit         boolean
708
709       Default value             N/A
710
711       Applicable socket types   all
712
713
714   ZMQ_RCVTIMEO: Maximum time before a socket operation returns with EAGAIN
715       Retrieve the timeout for recv operation on the socket. If the value is
716       0, zmq_recv(3) will return immediately, with a EAGAIN error if there is
717       no message to receive. If the value is -1, it will block until a
718       message is available. For all other values, it will wait for a message
719       for that amount of time before returning with an EAGAIN error.
720
721
722       Option value type         int
723
724       Option value unit         milliseconds
725
726       Default value             -1 (infinite)
727
728       Applicable socket types   all
729
730
731   ZMQ_RECONNECT_IVL: Retrieve reconnection interval
732       The ZMQ_RECONNECT_IVL option shall retrieve the initial reconnection
733       interval for the specified socket. The reconnection interval is the
734       period 0MQ shall wait between attempts to reconnect disconnected peers
735       when using connection-oriented transports. The value -1 means no
736       reconnection.
737
738           Note
739           The reconnection interval may be randomized by 0MQ to prevent
740           reconnection storms in topologies with a large number of peers per
741           socket.
742
743
744       Option value type         int
745
746       Option value unit         milliseconds
747
748       Default value             100
749
750       Applicable socket types   all, only for
751                                 connection-oriented
752                                 transports
753
754
755   ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval
756       The ZMQ_RECONNECT_IVL_MAX option shall retrieve the maximum
757       reconnection interval for the specified socket. This is the maximum
758       period 0MQ shall wait between attempts to reconnect. On each reconnect
759       attempt, the previous interval shall be doubled untill
760       ZMQ_RECONNECT_IVL_MAX is reached. This allows for exponential backoff
761       strategy. Default value means no exponential backoff is performed and
762       reconnect interval calculations are only based on ZMQ_RECONNECT_IVL.
763
764           Note
765           Values less than ZMQ_RECONNECT_IVL will be ignored.
766
767
768       Option value type         int
769
770       Option value unit         milliseconds
771
772       Default value             0 (only use
773                                 ZMQ_RECONNECT_IVL)
774
775       Applicable socket types   all, only for
776                                 connection-oriented
777                                 transport
778
779
780   ZMQ_RECONNECT_STOP: Retrieve condition where reconnection will stop
781       The ZMQ_RECONNECT_STOP option shall retrieve the conditions under which
782       automatic reconnection will stop.
783
784       The ZMQ_RECONNECT_STOP_CONN_REFUSED option will stop reconnection when
785       0MQ receives the ECONNREFUSED return code from the connect. This
786       indicates that there is no code bound to the specified endpoint.
787
788
789       Option value type         int
790
791       Option value unit         ZMQ_RECONNECT_STOP_CONN_REFUSED
792
793       Default value             0
794
795       Applicable socket types   all, only for
796                                 connection-oriented transports
797
798
799   ZMQ_RECOVERY_IVL: Get multicast recovery interval
800       The ZMQ_RECOVERY_IVL option shall retrieve the recovery interval for
801       multicast transports using the specified socket. The recovery interval
802       determines the maximum time in milliseconds that a receiver can be
803       absent from a multicast group before unrecoverable data loss will
804       occur.
805
806
807       Option value type         int
808
809       Option value unit         milliseconds
810
811       Default value             10000
812
813       Applicable socket types   all, when using multicast
814                                 transports
815
816
817   ZMQ_ROUTING_ID: Retrieve socket routing id
818       The ZMQ_ROUTING_ID option shall retrieve the routing id of the
819       specified socket. Routing ids are used only by the request/reply
820       pattern. Specifically, it can be used in tandem with ROUTER socket to
821       route messages to the peer with a specific routing id.
822
823       A routing id must be at least one byte and at most 255 bytes long.
824       Identities starting with a zero byte are reserved for use by the 0MQ
825       infrastructure.
826
827
828       Option value type         binary data
829
830       Option value unit         N/A
831
832       Default value             NULL
833
834       Applicable socket types   ZMQ_REP, ZMQ_REQ,
835                                 ZMQ_ROUTER, ZMQ_DEALER.
836
837
838   ZMQ_SNDBUF: Retrieve kernel transmit buffer size
839       The ZMQ_SNDBUF option shall retrieve the underlying kernel transmit
840       buffer size for the specified socket. For details refer to your
841       operating system documentation for the SO_SNDBUF socket option.
842
843
844       Option value type         int
845
846       Option value unit         bytes
847
848       Default value             8192
849
850       Applicable socket types   all
851
852
853   ZMQ_SNDHWM: Retrieves high water mark for outbound messages
854       The ZMQ_SNDHWM option shall return the high water mark for outbound
855       messages on the specified socket. The high water mark is a hard limit
856       on the maximum number of outstanding messages 0MQ shall queue in memory
857       for any single peer that the specified socket is communicating with. A
858       value of zero means no limit.
859
860       If this limit has been reached the socket shall enter an exceptional
861       state and depending on the socket type, 0MQ shall take appropriate
862       action such as blocking or dropping sent messages. Refer to the
863       individual socket descriptions in zmq_socket(3) for details on the
864       exact action taken for each socket type.
865
866
867       Option value type         int
868
869       Option value unit         messages
870
871       Default value             1000
872
873
874       Applicable socket types   all
875
876
877   ZMQ_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN
878       Retrieve the timeout for send operation on the socket. If the value is
879       0, zmq_send(3) will return immediately, with a EAGAIN error if the
880       message cannot be sent. If the value is -1, it will block until the
881       message is sent. For all other values, it will try to send the message
882       for that amount of time before returning with an EAGAIN error.
883
884
885       Option value type         int
886
887       Option value unit         milliseconds
888
889       Default value             -1 (infinite)
890
891       Applicable socket types   all
892
893
894   ZMQ_SOCKS_PROXY: Retrieve SOCKS5 proxy address
895       The ZMQ_SOCKS_PROXY option shall retrieve the SOCKS5 proxy address in
896       string format. The returned value shall be a NULL-terminated string and
897       MAY be empty. The returned size SHALL include the terminating null
898       byte.
899
900
901       Option value type         NULL-terminated character
902                                 string
903
904       Option value unit         N/A
905
906       Default value             null string
907
908       Applicable socket types   all, when using TCP
909                                 transports
910
911
912   ZMQ_TCP_KEEPALIVE: Override SO_KEEPALIVE socket option
913       Override SO_KEEPALIVE socket option(where supported by OS). The default
914       value of -1 means to skip any overrides and leave it to OS default.
915
916
917       Option value type         int
918
919       Option value unit         -1,0,1
920
921       Default value             -1 (leave to OS default)
922
923       Applicable socket types   all, when using TCP
924                                 transports.
925
926
927   ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket option
928       Override TCP_KEEPCNT socket option(where supported by OS). The default
929       value of -1 means to skip any overrides and leave it to OS default.
930
931
932       Option value type         int
933
934       Option value unit         -1,>0
935
936       Default value             -1 (leave to OS default)
937
938       Applicable socket types   all, when using TCP
939                                 transports.
940
941
942   ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
943       Override TCP_KEEPIDLE(or TCP_KEEPALIVE on some OS) socket option (where
944       supported by OS). The default value of -1 means to skip any overrides
945       and leave it to OS default.
946
947
948       Option value type         int
949
950       Option value unit         -1,>0
951
952       Default value             -1 (leave to OS default)
953
954       Applicable socket types   all, when using TCP
955                                 transports.
956
957
958   ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option
959       Override TCP_KEEPINTVL socket option(where supported by OS). The
960       default value of -1 means to skip any overrides and leave it to OS
961       default.
962
963
964       Option value type         int
965
966       Option value unit         -1,>0
967
968       Default value             -1 (leave to OS default)
969
970       Applicable socket types   all, when using TCP
971                                 transports.
972
973
974   ZMQ_TCP_MAXRT: Retrieve Max TCP Retransmit Timeout
975       On OSes where it is supported, retrieves how long before an
976       unacknowledged TCP retransmit times out. The system normally attempts
977       many TCP retransmits following an exponential backoff strategy. This
978       means that after a network outage, it may take a long time before the
979       session can be re-established. Setting this option allows the timeout
980       to happen at a shorter interval.
981
982
983       Option value type         int
984
985       Option value unit         milliseconds
986
987       Default value             0 (leave to OS default)
988
989       Applicable socket types   all, when using TCP
990                                 transports.
991
992
993   ZMQ_THREAD_SAFE: Retrieve socket thread safety
994       The ZMQ_THREAD_SAFE option shall retrieve a boolean value indicating
995       whether or not the socket is threadsafe. See zmq_socket(3) for which
996       sockets are thread-safe.
997
998
999       Option value type         int
1000
1001       Option value unit         boolean
1002
1003       Applicable socket types   all
1004
1005
1006   ZMQ_TOS: Retrieve the Type-of-Service socket override status
1007       Retrieve the IP_TOS option for the socket.
1008
1009
1010       Option value type         int
1011
1012       Option value unit         >0
1013
1014       Default value             0
1015
1016       Applicable socket types   all, only for
1017                                 connection-oriented
1018                                 transports
1019
1020
1021   ZMQ_TYPE: Retrieve socket type
1022       The ZMQ_TYPE option shall retrieve the socket type for the specified
1023       socket. The socket type is specified at socket creation time and cannot
1024       be modified afterwards.
1025
1026
1027       Option value type         int
1028
1029       Option value unit         N/A
1030
1031       Default value             N/A
1032
1033       Applicable socket types   all
1034
1035
1036   ZMQ_ZAP_DOMAIN: Retrieve RFC 27 authentication domain
1037       The ZMQ_ZAP_DOMAIN option shall retrieve the last ZAP domain set for
1038       the socket. The returned value shall be a NULL-terminated string and
1039       MAY be empty. An empty string means that ZAP authentication is
1040       disabled. The returned size SHALL include the terminating null byte.
1041
1042
1043       Option value type         character string
1044
1045       Option value unit         N/A
1046
1047       Default value             not set
1048
1049       Applicable socket types   all, when using TCP
1050                                 transport
1051
1052
1053   ZMQ_ZAP_ENFORCE_DOMAIN: Retrieve ZAP domain handling mode
1054       The ZMQ_ZAP_ENFORCE_DOMAIN option shall retrieve the flag that
1055       determines whether a ZAP domain is strictly required or not.
1056
1057
1058       Option value type         int
1059
1060       Option value unit         0, 1
1061
1062       Default value             0
1063
1064       Applicable socket types   all, when using ZAP
1065
1066
1067   ZMQ_VMCI_BUFFER_SIZE: Retrieve buffer size of the VMCI socket
1068       The ZMQ_VMCI_BUFFER_SIZE option shall retrieve the size of the
1069       underlying buffer for the socket. Used during negotiation before the
1070       connection is established.
1071
1072
1073       Option value type         uint64_t
1074
1075       Option value unit         bytes
1076
1077
1078       Default value             65546
1079
1080       Applicable socket types   all, when using VMCI
1081                                 transport
1082
1083
1084   ZMQ_VMCI_BUFFER_MIN_SIZE: Retrieve min buffer size of the VMCI socket
1085       The ZMQ_VMCI_BUFFER_MIN_SIZE option shall retrieve the min size of the
1086       underlying buffer for the socket. Used during negotiation before the
1087       connection is established.
1088
1089
1090       Option value type         uint64_t
1091
1092       Option value unit         bytes
1093
1094       Default value             128
1095
1096       Applicable socket types   all, when using VMCI
1097                                 transport
1098
1099
1100   ZMQ_VMCI_BUFFER_MAX_SIZE: Retrieve max buffer size of the VMCI socket
1101       The ZMQ_VMCI_BUFFER_MAX_SIZE option shall retrieve the max size of the
1102       underlying buffer for the socket. Used during negotiation before the
1103       connection is established.
1104
1105
1106       Option value type         uint64_t
1107
1108       Option value unit         bytes
1109
1110       Default value             262144
1111
1112       Applicable socket types   all, when using VMCI
1113                                 transport
1114
1115
1116   ZMQ_VMCI_CONNECT_TIMEOUT: Retrieve connection timeout of the VMCI socket
1117       The ZMQ_VMCI_CONNECT_TIMEOUT option shall retrieve connection timeout
1118       for the socket.
1119
1120
1121       Option value type         int
1122
1123       Option value unit         milliseconds
1124
1125       Default value             -1
1126
1127       Applicable socket types   all, when using VMCI
1128                                 transport
1129
1130
1131   ZMQ_MULTICAST_LOOP: Retrieve multicast local loopback configuration
1132       Retrieve the current multicast loopback configuration. A value of 1
1133       means that the multicast packets sent on this socket will be looped
1134       back to local listening interface.
1135
1136
1137       Option value type         int
1138
1139       Option value unit         0, 1
1140
1141       Default value             1
1142
1143
1144
1145
1146       Applicable socket types   ZMQ_RADIO, when using UDP
1147                                 multicast transport
1148
1149
1150   ZMQ_ROUTER_NOTIFY: Retrieve router socket notification settings
1151       Retrieve the current notification settings of a router socket. The
1152       returned value is a bitmask composed of ZMQ_NOTIFY_CONNECT and
1153       ZMQ_NOTIFY_DISCONNECT flags, meaning connect and disconnect
1154       notifications are enabled, respectively. A value of 0 means the
1155       notifications are off.
1156
1157           Note
1158           in DRAFT state, not yet available in stable releases.
1159
1160
1161       Option value type         int
1162
1163       Option value unit         0, ZMQ_NOTIFY_CONNECT,
1164                                 ZMQ_NOTIFY_DISCONNECT,
1165                                 ZMQ_NOTIFY_CONNECT |
1166                                 ZMQ_NOTIFY_DISCONNECT
1167
1168       Default value             0
1169
1170       Applicable socket types   ZMQ_ROUTER
1171
1172
1173   ZMQ_IN_BATCH_SIZE: Maximal receive batch size
1174       Gets the maximal amount of messages that can be received in a single
1175       recv system call.
1176
1177       Cannot be zero.
1178
1179           Note
1180           in DRAFT state, not yet available in stable releases.
1181
1182
1183       Option value type         int
1184
1185       Option value unit         messages
1186
1187       Default value             8192
1188
1189       Applicable socket types   All, when using TCP, IPC,
1190                                 PGM or NORM transport.
1191
1192
1193   ZMQ_OUT_BATCH_SIZE: Maximal send batch size
1194       Gets the maximal amount of messages that can be sent in a single send
1195       system call.
1196
1197       Cannot be zero.
1198
1199           Note
1200           in DRAFT state, not yet available in stable releases.
1201
1202
1203       Option value type         int
1204
1205       Option value unit         messages
1206
1207       Default value             8192
1208
1209       Applicable socket types   All, when using TCP, IPC,
1210                                 PGM or NORM transport.
1211
1212

RETURN VALUE

1214       The zmq_getsockopt() function shall return zero if successful.
1215       Otherwise it shall return -1 and set errno to one of the values defined
1216       below.
1217

ERRORS

1219       EINVAL
1220           The requested option option_name is unknown, or the requested
1221           option_len or option_value is invalid, or the size of the buffer
1222           pointed to by option_value, as specified by option_len, is
1223           insufficient for storing the option value.
1224
1225       ETERM
1226           The 0MQ context associated with the specified socket was
1227           terminated.
1228
1229       ENOTSOCK
1230           The provided socket was invalid.
1231
1232       EINTR
1233           The operation was interrupted by delivery of a signal.
1234

EXAMPLE

1236       Retrieving the high water mark for outgoing messages.
1237
1238           /* Retrieve high water mark into sndhwm */
1239           int sndhwm;
1240           size_t sndhwm_size = sizeof (sndhwm);
1241           rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
1242           assert (rc == 0);
1243
1244

SEE ALSO

1246       zmq_setsockopt(3) zmq_socket(3) zmq(7)
1247

AUTHORS

1249       This page was written by the 0MQ community. To make a change please
1250       read the 0MQ Contribution Policy at
1251       http://www.zeromq.org/docs:contributing.
1252
1253
1254
12550MQ 4.3.4                         01/21/2023                 ZMQ_GETSOCKOPT(3)
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