1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
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
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
zmq_getsockopt(3)
=================
NAME
----
zmq_getsockopt - get 0MQ socket options
SYNOPSIS
--------
*int zmq_getsockopt (void '*socket', int 'option_name', void '*option_value', size_t '*option_len');*
DESCRIPTION
-----------
The _zmq_getsockopt()_ function shall retrieve the value for the option
specified by the 'option_name' argument for the 0MQ socket pointed to by the
'socket' argument, and store it in the buffer pointed to by the 'option_value'
argument. The 'option_len' argument is the size in bytes of the buffer pointed
to by 'option_value'; upon successful completion _zmq_getsockopt()_ shall
modify the 'option_len' argument to indicate the actual size of the option
value stored in the buffer.
The following options can be retrieved with the _zmq_getsockopt()_ function:
ZMQ_AFFINITY: Retrieve I/O thread affinity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_AFFINITY' option shall retrieve the I/O thread affinity for newly
created connections on the specified 'socket'.
Affinity determines which threads from the 0MQ I/O thread pool associated with
the socket's _context_ shall handle newly created connections. A value of zero
specifies no affinity, meaning that work shall be distributed fairly among all
0MQ I/O threads in the thread pool. For non-zero values, the lowest bit
corresponds to thread 1, second lowest bit to thread 2 and so on. For example,
a value of 3 specifies that subsequent connections on 'socket' shall be handled
exclusively by I/O threads 1 and 2.
See also linkzmq:zmq_init[3] for details on allocating the number of I/O
threads for a specific _context_.
[horizontal]
Option value type:: uint64_t
Option value unit:: N/A (bitmap)
Default value:: 0
Applicable socket types:: N/A
ZMQ_BACKLOG: Retrieve maximum length of the queue of outstanding connections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_BACKLOG' option shall retrieve the maximum length of the queue of
outstanding peer connections for the specified 'socket'; this only applies to
connection-oriented transports. For details refer to your operating system
documentation for the 'listen' function.
[horizontal]
Option value type:: int
Option value unit:: connections
Default value:: 100
Applicable socket types:: all, only for connection-oriented transports
ZMQ_BINDTODEVICE: Retrieve name of device the socket is bound to
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_BINDTODEVICE' option retrieves the name of the device this socket is
bound to, eg. an interface or VRF. If a socket is bound to an interface, only
packets received from that interface are processed by the socket. If device
is a VRF device, then subsequent binds/connects to that socket use addresses
in the VRF routing table.
[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.
ZMQ_CONNECT_TIMEOUT: Retrieve connect() timeout
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieves how long to wait before timing-out a connect() system call.
The connect() system call normally takes a long time before it returns a
time out error. Setting this option allows the library to time out the call
at an earlier interval.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0 (disabled)
Applicable socket types:: all, when using TCP transports.
ZMQ_CURVE_PUBLICKEY: Retrieve current CURVE public key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieves the current long term public key for the socket. You can
provide either a 32 byte buffer, to retrieve the binary key value, or
a 41 byte buffer, to retrieve the key in a printable Z85 format.
NOTE: to fetch a printable key, the buffer must be 41 bytes large
to hold the 40-char key value and one null byte.
[horizontal]
Option value type:: binary data or Z85 text string
Option value size:: 32 or 41
Default value:: null
Applicable socket types:: all, when using TCP transport
ZMQ_CURVE_SECRETKEY: Retrieve current CURVE secret key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieves the current long term secret key for the socket. You can
provide either a 32 byte buffer, to retrieve the binary key value, or
a 41 byte buffer, to retrieve the key in a printable Z85 format.
NOTE: to fetch a printable key, the buffer must be 41 bytes large
to hold the 40-char key value and one null byte.
[horizontal]
Option value type:: binary data or Z85 text string
Option value size:: 32 or 41
Default value:: null
Applicable socket types:: all, when using TCP transport
ZMQ_CURVE_SERVERKEY: Retrieve current CURVE server key
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieves the current server key for the client socket. You can
provide either a 32 byte buffer, to retrieve the binary key value, or
a 41-byte buffer, to retrieve the key in a printable Z85 format.
NOTE: to fetch a printable key, the buffer must be 41 bytes large
to hold the 40-char key value and one null byte.
[horizontal]
Option value type:: binary data or Z85 text string
Option value size:: 32 or 41
Default value:: null
Applicable socket types:: all, when using TCP transport
ZMQ_EVENTS: Retrieve socket event state
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_EVENTS' option shall retrieve the event state for the specified
'socket'. The returned value is a bit mask constructed by OR'ing a combination
of the following event flags:
*ZMQ_POLLIN*::
Indicates that at least one message may be received from the specified socket
without blocking.
*ZMQ_POLLOUT*::
Indicates that at least one message may be sent to the specified socket without
blocking.
The combination of a file descriptor returned by the 'ZMQ_FD' option being
ready for reading but no actual events returned by a subsequent retrieval of
the 'ZMQ_EVENTS' option is valid; applications should simply ignore this case
and restart their polling operation/event loop.
[horizontal]
Option value type:: int
Option value unit:: N/A (flags)
Default value:: N/A
Applicable socket types:: all
ZMQ_FD: Retrieve file descriptor associated with the socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_FD' option shall retrieve the file descriptor associated with the
specified 'socket'. The returned file descriptor can be used to integrate the
socket into an existing event loop; the 0MQ library shall signal any pending
events on the socket in an _edge-triggered_ fashion by making the file
descriptor become ready for reading.
NOTE: The ability to read from the returned file descriptor does not
necessarily indicate that messages are available to be read from, or can be
written to, the underlying socket; applications must retrieve the actual event
state with a subsequent retrieval of the 'ZMQ_EVENTS' option.
NOTE: The returned file descriptor is also used internally by the 'zmq_send'
and 'zmq_recv' functions. As the descriptor is edge triggered, applications
must update the state of 'ZMQ_EVENTS' after each invocation of 'zmq_send'
or 'zmq_recv'.To be more explicit: after calling 'zmq_send' the socket may
become readable (and vice versa) without triggering a read event on the
file descriptor.
CAUTION: The returned file descriptor is intended for use with a 'poll' or
similar system call only. Applications must never attempt to read or write data
to it directly, neither should they try to close it.
[horizontal]
Option value type:: int on POSIX systems, SOCKET on Windows
Option value unit:: N/A
Default value:: N/A
Applicable socket types:: all
ZMQ_GSSAPI_PLAINTEXT: Retrieve GSSAPI plaintext or encrypted status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the 'ZMQ_GSSAPI_PLAINTEXT' option, if any, previously set on the
socket. A value of '1' means that communications will be plaintext. A value
of '0' means communications will be encrypted.
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0 (false)
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_GSSAPI_PRINCIPAL: Retrieve the name of the GSSAPI principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_GSSAPI_PRINCIPAL' option shall retrieve the principal name set for the
GSSAPI security mechanism. The returned value shall be a NULL-terminated string
and MAY be empty. The returned size SHALL include the terminating null byte.
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_GSSAPI_SERVER: Retrieve current GSSAPI server role
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the 'ZMQ_GSSAPI_SERVER' option, if any, previously set on the socket.
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0 (false)
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_GSSAPI_SERVICE_PRINCIPAL: Retrieve the name of the GSSAPI service principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_GSSAPI_SERVICE_PRINCIPAL' option shall retrieve the principal name of
the GSSAPI server to which a GSSAPI client socket intends to connect. The
returned value shall be a NULL-terminated string and MAY be empty. The returned
size SHALL include the terminating null byte.
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Retrieve nametype for service principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the 'ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE' option, if any, previously
set on the socket. A value of 'ZMQ_GSSAPI_NT_HOSTBASED' (0) means the name
specified with 'ZMQ_GSSAPI_SERVICE_PRINCIPAL' is interpreted as a host based
name. A value of 'ZMQ_GSSAPI_NT_USER_NAME' (1) means it is interpreted as
a local user name. A value of 'ZMQ_GSSAPI_NT_KRB5_PRINCIPAL' (2) means it
is interpreted as an unparsed principal name string (valid only with the
krb5 GSSAPI mechanism).
[horizontal]
Option value type:: int
Option value unit:: 0, 1, 2
Default value:: 0 (ZMQ_GSSAPI_NT_HOSTBASED)
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Retrieve nametype for service principal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the 'ZMQ_GSSAPI_PRINCIPAL_NAMETYPE' option, if any, previously
set on the socket. A value of 'ZMQ_GSSAPI_NT_HOSTBASED' (0) means the name
specified with 'ZMQ_GSSAPI_PRINCIPAL' is interpreted as a host based
name. A value of 'ZMQ_GSSAPI_NT_USER_NAME' (1) means it is interpreted as
a local user name. A value of 'ZMQ_GSSAPI_NT_KRB5_PRINCIPAL' (2) means it
is interpreted as an unparsed principal name string (valid only with the
krb5 GSSAPI mechanism).
[horizontal]
Option value type:: int
Option value unit:: 0, 1, 2
Default value:: 0 (ZMQ_GSSAPI_NT_HOSTBASED)
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_HANDSHAKE_IVL: Retrieve maximum handshake interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_HANDSHAKE_IVL' option shall retrieve the maximum handshake interval
for the specified 'socket'. Handshaking is the exchange of socket configuration
information (socket type, routing id, security) that occurs when a connection
is first opened, only for connection-oriented transports. If handshaking does
not complete within the configured time, the connection shall be closed.
The value 0 means no handshake time limit.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 30000
Applicable socket types:: all but ZMQ_STREAM, only for connection-oriented transports
ZMQ_IDENTITY: Retrieve socket identity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This option name is now deprecated. Use ZMQ_ROUTING_ID instead.
ZMQ_IDENTITY remains as an alias for now.
ZMQ_IMMEDIATE: Retrieve attach-on-connect value
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the state of the attach on connect value. If set to `1`, will delay the
attachment of a pipe on connect until the underlying connection has completed.
This will cause the socket to block if there are no other connections, but will
prevent queues from filling on pipes awaiting connection.
[horizontal]
Option value type:: int
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, primarily when using TCP/IPC transports.
ZMQ_INVERT_MATCHING: Retrieve inverted filtering status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the value of the 'ZMQ_INVERT_MATCHING' option. A value of `1`
means the socket uses inverted prefix matching.
On 'PUB' and 'XPUB' sockets, this causes messages to be sent to all
connected sockets 'except' those subscribed to a prefix that matches
the message. On 'SUB' sockets, this causes only incoming messages that
do 'not' match any of the socket's subscriptions to be received by the user.
Whenever 'ZMQ_INVERT_MATCHING' is set to 1 on a 'PUB' socket, all 'SUB'
sockets connecting to it must also have the option set to 1. Failure to
do so will have the 'SUB' sockets reject everything the 'PUB' socket sends
them. 'XSUB' sockets do not need to do this because they do not filter
incoming messages.
[horizontal]
Option value type:: int
Option value unit:: 0,1
Default value:: 0
Applicable socket types:: ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB
ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the IPv4-only option for the socket. This option is deprecated.
Please use the ZMQ_IPV6 option.
[horizontal]
Option value type:: int
Option value unit:: boolean
Default value:: 1 (true)
Applicable socket types:: all, when using TCP transports.
ZMQ_IPV6: Retrieve IPv6 socket status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the IPv6 option for the socket. A value of `1` means IPv6 is
enabled on the socket, while `0` means the socket will use only IPv4.
When IPv6 is enabled the socket will connect to, or accept connections
from, both IPv4 and IPv6 hosts.
[horizontal]
Option value type:: int
Option value unit:: boolean
Default value:: 0 (false)
Applicable socket types:: all, when using TCP transports.
ZMQ_LAST_ENDPOINT: Retrieve the last endpoint set
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_LAST_ENDPOINT' option shall retrieve the last endpoint bound for
TCP and IPC transports. The returned value will be a string in the form of
a ZMQ DSN. Note that if the TCP host is INADDR_ANY, indicated by a *, then
the returned address will be 0.0.0.0 (for IPv4).
Note: not supported on GNU/Hurd with IPC due to non-working getsockname().
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: NULL
Applicable socket types:: all, when binding TCP or IPC transports
ZMQ_LINGER: Retrieve linger period for socket shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_LINGER' option shall retrieve the linger period for the specified
'socket'. The linger period determines how long pending messages which have
yet to be sent to a peer shall linger in memory after a socket is closed with
linkzmq:zmq_close[3], and further affects the termination of the socket's
context with linkzmq:zmq_ctx_term[3]. The following outlines the different
behaviours:
* The default value of '-1' specifies an infinite linger period. Pending
messages shall not be discarded after a call to _zmq_close()_; attempting to
terminate the socket's context with _zmq_ctx_term()_ shall block until all
pending messages have been sent to a peer.
* The value of '0' specifies no linger period. Pending messages shall be
discarded immediately when the socket is closed with _zmq_close()_.
* Positive values specify an upper bound for the linger period in milliseconds.
Pending messages shall not be discarded after a call to _zmq_close()_;
attempting to terminate the socket's context with _zmq_ctx_term()_ shall block
until either all pending messages have been sent to a peer, or the linger
period expires, after which any pending messages shall be discarded.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The option shall retrieve limit for the inbound messages. If a peer sends
a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
'no limit'.
[horizontal]
Option value type:: int64_t
Option value unit:: bytes
Default value:: -1
Applicable socket types:: all
ZMQ_MECHANISM: Retrieve current security mechanism
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MECHANISM' option shall retrieve the current security mechanism
for the socket.
[horizontal]
Option value type:: int
Option value unit:: ZMQ_NULL, ZMQ_PLAIN, ZMQ_CURVE, or ZMQ_GSSAPI
Default value:: ZMQ_NULL
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The option shall retrieve time-to-live used for outbound multicast packets.
The default of 1 means that the multicast packets don't leave the local network.
[horizontal]
Option value type:: int
Option value unit:: network hops
Default value:: 1
Applicable socket types:: all, when using multicast transports
ZMQ_MULTICAST_MAXTPDU: Maximum transport data unit size for multicast packets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MULTICAST_MAXTPDU' option shall retrieve the maximum transport
data unit size used for outbound multicast packets.
This must be set at or below the minimum Maximum Transmission Unit (MTU) for
all network paths over which multicast reception is required.
[horizontal]
Option value type:: int
Option value unit:: bytes
Default value:: 1500
Applicable socket types:: all, when using multicast transports
ZMQ_PLAIN_PASSWORD: Retrieve current password
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_PLAIN_PASSWORD' option shall retrieve the last password set for
the PLAIN security mechanism. The returned value shall be a NULL-terminated
string and MAY be empty. The returned size SHALL include the terminating
null byte.
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_PLAIN_SERVER: Retrieve current PLAIN server role
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Returns the 'ZMQ_PLAIN_SERVER' option, if any, previously set on the socket.
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: int
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_PLAIN_USERNAME: Retrieve current PLAIN username
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_PLAIN_USERNAME' option shall retrieve the last username set for
the PLAIN security mechanism. The returned value shall be a NULL-terminated
string and MAY be empty. The returned size SHALL include the terminating
null byte.
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP or IPC transports
ZMQ_USE_FD: Retrieve the pre-allocated socket file descriptor
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_USE_FD' option shall retrieve the pre-allocated file
descriptor that has been assigned to a ZMQ socket, if any. -1 shall be
returned if a pre-allocated file descriptor was not set for the socket.
[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
ZMQ_RATE: Retrieve multicast data rate
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RATE' option shall retrieve the maximum send or receive data rate for
multicast transports using the specified 'socket'.
[horizontal]
Option value type:: int
Option value unit:: kilobits per second
Default value:: 100
Applicable socket types:: all, when using multicast transports
ZMQ_RCVBUF: Retrieve kernel receive buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVBUF' option shall retrieve the underlying kernel receive buffer
size for the specified 'socket'. For details refer to your operating system
documentation for the 'SO_RCVBUF' socket option.
[horizontal]
Option value type:: int
Option value unit:: bytes
Default value:: 8192
Applicable socket types:: all
ZMQ_RCVHWM: Retrieve high water mark for inbound messages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVHWM' option shall return the high water mark for inbound messages on
the specified 'socket'. The high water mark is a hard limit on the maximum
number of outstanding messages 0MQ shall queue in memory for any single peer
that the specified 'socket' is communicating with. A value of zero means no
limit.
If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, 0MQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket descriptions
in linkzmq:zmq_socket[3] for details on the exact action taken for each socket
type.
[horizontal]
Option value type:: int
Option value unit:: messages
Default value:: 1000
Applicable socket types:: all
ZMQ_RCVMORE: More message data parts to follow
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RCVMORE' option shall return True (1) if the message part last
received from the 'socket' was a data part with more parts to follow. If there
are no data parts to follow, this option shall return False (0).
Refer to linkzmq:zmq_send[3] and linkzmq:zmq_recv[3] for a detailed description
of multi-part messages.
[horizontal]
Option value type:: int
Option value unit:: boolean
Default value:: N/A
Applicable socket types:: all
ZMQ_RCVTIMEO: Maximum time before a socket operation returns with EAGAIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the timeout for recv operation on the socket. If the value is `0`,
_zmq_recv(3)_ will return immediately, with a EAGAIN error if there is no
message to receive. If the value is `-1`, it will block until a message is
available. For all other values, it will wait for a message for that amount
of time before returning with an EAGAIN error.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
ZMQ_RECONNECT_IVL: Retrieve reconnection interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECONNECT_IVL' option shall retrieve the initial reconnection interval
for the specified 'socket'. The reconnection interval is the period 0MQ shall
wait between attempts to reconnect disconnected peers when using
connection-oriented transports. The value -1 means no reconnection.
NOTE: The reconnection interval may be randomized by 0MQ to prevent
reconnection storms in topologies with a large number of peers per socket.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 100
Applicable socket types:: all, only for connection-oriented transports
ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECONNECT_IVL_MAX' option shall retrieve the maximum reconnection
interval for the specified 'socket'. This is the maximum period 0MQ shall wait
between attempts to reconnect. On each reconnect attempt, the previous interval
shall be doubled untill ZMQ_RECONNECT_IVL_MAX is reached. This allows for
exponential backoff strategy. Default value means no exponential backoff is
performed and reconnect interval calculations are only based on
ZMQ_RECONNECT_IVL.
NOTE: Values less than ZMQ_RECONNECT_IVL will be ignored.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0 (only use ZMQ_RECONNECT_IVL)
Applicable socket types:: all, only for connection-oriented transport
ZMQ_RECOVERY_IVL: Get multicast recovery interval
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_RECOVERY_IVL' option shall retrieve the recovery interval for
multicast transports using the specified 'socket'. The recovery interval
determines the maximum time in milliseconds that a receiver can be absent from a
multicast group before unrecoverable data loss will occur.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 10000
Applicable socket types:: all, when using multicast transports
ZMQ_ROUTING_ID: Retrieve socket routing id
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_ROUTING_ID' option shall retrieve the routing id of the specified 'socket'.
Routing ids are used only by the request/reply pattern. Specifically, it can be used
in tandem with ROUTER socket to route messages to the peer with a specific
routing id.
A routing id must be at least one byte and at most 255 bytes long. Identities
starting with a zero byte are reserved for use by the 0MQ infrastructure.
[horizontal]
Option value type:: binary data
Option value unit:: N/A
Default value:: NULL
Applicable socket types:: ZMQ_REP, ZMQ_REQ, ZMQ_ROUTER, ZMQ_DEALER.
ZMQ_SNDBUF: Retrieve kernel transmit buffer size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SNDBUF' option shall retrieve the underlying kernel transmit buffer
size for the specified 'socket'. For details refer to your operating system
documentation for the 'SO_SNDBUF' socket option.
[horizontal]
Option value type:: int
Option value unit:: bytes
Default value:: 8192
Applicable socket types:: all
ZMQ_SNDHWM: Retrieves high water mark for outbound messages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SNDHWM' option shall return the high water mark for outbound messages
on the specified 'socket'. The high water mark is a hard limit on the maximum
number of outstanding messages 0MQ shall queue in memory for any single peer
that the specified 'socket' is communicating with. A value of zero means no
limit.
If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, 0MQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket descriptions
in linkzmq:zmq_socket[3] for details on the exact action taken for each socket
type.
[horizontal]
Option value type:: int
Option value unit:: messages
Default value:: 1000
Applicable socket types:: all
ZMQ_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the timeout for send operation on the socket. If the value is `0`,
_zmq_send(3)_ will return immediately, with a EAGAIN error if the message
cannot be sent. If the value is `-1`, it will block until the message is sent.
For all other values, it will try to send the message for that amount of time
before returning with an EAGAIN error.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: -1 (infinite)
Applicable socket types:: all
ZMQ_SOCKS_PROXY: Retrieve SOCKS5 proxy address
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SOCKS_PROXY' option shall retrieve the SOCKS5 proxy address in string
format. The returned value shall be a NULL-terminated string and MAY be empty.
The returned size SHALL include the terminating null byte.
[horizontal]
Option value type:: NULL-terminated character string
Option value unit:: N/A
Default value:: null string
Applicable socket types:: all, when using TCP transports
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.
[horizontal]
Option value type:: int
Option value unit:: -1,0,1
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket option
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Override 'TCP_KEEPCNT' socket option(where supported by OS).
The default value of `-1` means to skip any overrides and leave it to OS default.
[horizontal]
Option value type:: int
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPIDLE (or TCP_KEEPALIVE on some OS)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Override 'TCP_KEEPIDLE'(or 'TCP_KEEPALIVE' on some OS) socket option (where
supported by OS). The default value of `-1` means to skip any overrides and
leave it to OS default.
[horizontal]
Option value type:: int
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Override 'TCP_KEEPINTVL' socket option(where supported by OS).
The default value of `-1` means to skip any overrides and leave it to OS default.
[horizontal]
Option value type:: int
Option value unit:: -1,>0
Default value:: -1 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
ZMQ_TCP_MAXRT: Retrieve Max TCP Retransmit Timeout
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On OSes where it is supported, retrieves how long before an unacknowledged TCP
retransmit times out. The system normally attempts many TCP retransmits
following an exponential backoff strategy. This means that after a network
outage, it may take a long time before the session can be re-established.
Setting this option allows the timeout to happen at a shorter interval.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: 0 (leave to OS default)
Applicable socket types:: all, when using TCP transports.
ZMQ_THREAD_SAFE: Retrieve socket thread safety
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_THREAD_SAFE' option shall retrieve a boolean value indicating whether
or not the socket is threadsafe. Currently 'ZMQ_CLIENT' and 'ZMQ_SERVER' sockets
are threadsafe.
[horizontal]
Option value type:: boolean
Applicable socket types:: all
ZMQ_TOS: Retrieve the Type-of-Service socket override status
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the IP_TOS option for the socket.
[horizontal]
Option value type:: int
Option value unit:: >0
Default value:: 0
Applicable socket types:: all, only for connection-oriented transports
ZMQ_TYPE: Retrieve socket type
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_TYPE' option shall retrieve the socket type for the specified
'socket'. The socket type is specified at socket creation time and
cannot be modified afterwards.
[horizontal]
Option value type:: int
Option value unit:: N/A
Default value:: N/A
Applicable socket types:: all
ZMQ_ZAP_DOMAIN: Retrieve RFC 27 authentication domain
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_ZAP_DOMAIN' option shall retrieve the last ZAP domain set for
the socket. The returned value shall be a NULL-terminated string and MAY
be empty. An empty string means that ZAP authentication is disabled.
The returned size SHALL include the terminating null byte.
[horizontal]
Option value type:: character string
Option value unit:: N/A
Default value:: not set
Applicable socket types:: all, when using TCP transport
ZMQ_ZAP_ENFORCE_DOMAIN: Retrieve ZAP domain handling mode
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_ZAP_ENFORCE_DOMAIN' option shall retrieve the flag that determines
whether a ZAP domain is strictly required or not.
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 0
Applicable socket types:: all, when using ZAP
ZMQ_VMCI_BUFFER_SIZE: Retrieve buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_SIZE` option shall retrieve the size of the underlying
buffer for the socket. Used during negotiation before the connection is established.
[horizontal]
Option value type:: uint64_t
Option value unit:: bytes
Default value:: 65546
Applicable socket types:: all, when using VMCI transport
ZMQ_VMCI_BUFFER_MIN_SIZE: Retrieve min buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_MIN_SIZE` option shall retrieve the min size of the underlying
buffer for the socket. Used during negotiation before the connection is established.
[horizontal]
Option value type:: uint64_t
Option value unit:: bytes
Default value:: 128
Applicable socket types:: all, when using VMCI transport
ZMQ_VMCI_BUFFER_MAX_SIZE: Retrieve max buffer size of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_BUFFER_MAX_SIZE` option shall retrieve the max size of the underlying
buffer for the socket. Used during negotiation before the connection is established.
[horizontal]
Option value type:: uint64_t
Option value unit:: bytes
Default value:: 262144
Applicable socket types:: all, when using VMCI transport
ZMQ_VMCI_CONNECT_TIMEOUT: Retrieve connection timeout of the VMCI socket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `ZMQ_VMCI_CONNECT_TIMEOUT` option shall retrieve connection timeout
for the socket.
[horizontal]
Option value type:: int
Option value unit:: milliseconds
Default value:: -1
Applicable socket types:: all, when using VMCI transport
ZMQ_MULTICAST_LOOP: Retrieve multicast local loopback configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the current multicast loopback configuration. A value of `1`
means that the multicast packets sent on this socket will be looped
back to local listening interface.
[horizontal]
Option value type:: int
Option value unit:: 0, 1
Default value:: 1
Applicable socket types:: ZMQ_RADIO, when using UDP multicast transport
ZMQ_ROUTER_NOTIFY: Retrieve router socket notification settings
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Retrieve the current notification settings of a router socket. The returned
value is a bitmask composed of ZMQ_NOTIFY_CONNECT and ZMQ_NOTIFY_DISCONNECT
flags, meaning connect and disconnect notifications are enabled, respectively.
A value of '0' means the notifications are off.
NOTE: in DRAFT state, not yet available in stable releases.
[horizontal]
Option value type:: int
Option value unit:: 0, ZMQ_NOTIFY_CONNECT, ZMQ_NOTIFY_DISCONNECT, ZMQ_NOTIFY_CONNECT|ZMQ_NOTIFY_DISCONNECT
Default value:: 0
Applicable socket types:: ZMQ_ROUTER
RETURN VALUE
------------
The _zmq_getsockopt()_ function shall return zero if successful. Otherwise it
shall return `-1` and set 'errno' to one of the values defined below.
ERRORS
------
*EINVAL*::
The requested option _option_name_ is unknown, or the requested _option_len_ or
_option_value_ is invalid, or the size of the buffer pointed to by
_option_value_, as specified by _option_len_, is insufficient for storing the
option value.
*ETERM*::
The 0MQ 'context' associated with the specified 'socket' was terminated.
*ENOTSOCK*::
The provided 'socket' was invalid.
*EINTR*::
The operation was interrupted by delivery of a signal.
EXAMPLE
-------
.Retrieving the high water mark for outgoing messages
----
/* Retrieve high water mark into sndhwm */
int sndhwm;
size_t sndhwm_size = sizeof (sndhwm);
rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
assert (rc == 0);
----
SEE ALSO
--------
linkzmq:zmq_setsockopt[3]
linkzmq:zmq_socket[3]
linkzmq:zmq[7]
AUTHORS
-------
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>.