'\" t
.\"     Title: zmq_setsockopt
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
.\"      Date: 04/04/2012
.\"    Manual: 0MQ Manual
.\"    Source: 0MQ 2.2.0
.\"  Language: English
.\"
.TH "ZMQ_SETSOCKOPT" "3" "04/04/2012" "0MQ 2\&.2\&.0" "0MQ Manual"
.\" -----------------------------------------------------------------
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.nh
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.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
zmq_setsockopt \- set 0MQ socket options
.SH "SYNOPSIS"
.sp
\fBint zmq_setsockopt (void \fR\fB\fI*socket\fR\fR\fB, int \fR\fB\fIoption_name\fR\fR\fB, const void \fR\fB\fI*option_value\fR\fR\fB, size_t \fR\fB\fIoption_len\fR\fR\fB);\fR
.sp
Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE and ZMQ_LINGER, only take effect for subsequent socket bind/connects\&.
.SH "DESCRIPTION"
.sp
The \fIzmq_setsockopt()\fR function shall set the option specified by the \fIoption_name\fR argument to the value pointed to by the \fIoption_value\fR argument for the 0MQ socket pointed to by the \fIsocket\fR argument\&. The \fIoption_len\fR argument is the size of the option value in bytes\&.
.sp
The following socket options can be set with the \fIzmq_setsockopt()\fR function:
.SS "ZMQ_HWM: Set high water mark"
.sp
The \fIZMQ_HWM\fR option shall set the high water mark for the specified \fIsocket\fR\&. 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 \fIsocket\fR is communicating with\&.
.sp
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 \fBzmq_socket\fR(3) for details on the exact action taken for each socket type\&.
.sp
The default \fIZMQ_HWM\fR value of zero means "no limit"\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
uint64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
messages
T}
T{
.sp
Default value
T}:T{
.sp
0
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_SWAP: Set disk offload size"
.sp
The \fIZMQ_SWAP\fR option shall set the disk offload (swap) size for the specified \fIsocket\fR\&. A socket which has \fIZMQ_SWAP\fR set to a non\-zero value may exceed its high water mark; in this case outstanding messages shall be offloaded to storage on disk rather than held in memory\&.
.sp
The value of \fIZMQ_SWAP\fR defines the maximum size of the swap space in bytes\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
bytes
T}
T{
.sp
Default value
T}:T{
.sp
0
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_AFFINITY: Set I/O thread affinity"
.sp
The \fIZMQ_AFFINITY\fR option shall set the I/O thread affinity for newly created connections on the specified \fIsocket\fR\&.
.sp
Affinity determines which threads from the 0MQ I/O thread pool associated with the socket\(cqs \fIcontext\fR 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 \fIsocket\fR shall be handled exclusively by I/O threads 1 and 2\&.
.sp
See also \fBzmq_init\fR(3) for details on allocating the number of I/O threads for a specific \fIcontext\fR\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
uint64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
N/A (bitmap)
T}
T{
.sp
Default value
T}:T{
.sp
0
T}
T{
.sp
Applicable socket types
T}:T{
.sp
N/A
T}
.TE
.sp 1
.SS "ZMQ_IDENTITY: Set socket identity"
.sp
The \fIZMQ_IDENTITY\fR option shall set the identity of the specified \fIsocket\fR\&. Socket identity determines if existing 0MQ infrastructure (\fImessage queues\fR, \fIforwarding devices\fR) shall be identified with a specific application and persist across multiple runs of the application\&.
.sp
If the socket has no identity, each run of an application is completely separate from other runs\&. However, with identity set the socket shall re\-use any existing 0MQ infrastructure configured by the previous run(s)\&. Thus the application may receive messages that were sent in the meantime, \fImessage queue\fR limits shall be shared with previous run(s) and so on\&.
.sp
Identity should be at least one byte and at most 255 bytes long\&. Identities starting with binary zero are reserved for use by 0MQ infrastructure\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
binary data
T}
T{
.sp
Option value unit
T}:T{
.sp
N/A
T}
T{
.sp
Default value
T}:T{
.sp
NULL
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_SUBSCRIBE: Establish message filter"
.sp
The \fIZMQ_SUBSCRIBE\fR option shall establish a new message filter on a \fIZMQ_SUB\fR socket\&. Newly created \fIZMQ_SUB\fR sockets shall filter out all incoming messages, therefore you should call this option to establish an initial message filter\&.
.sp
An empty \fIoption_value\fR of length zero shall subscribe to all incoming messages\&. A non\-empty \fIoption_value\fR shall subscribe to all messages beginning with the specified prefix\&. Multiple filters may be attached to a single \fIZMQ_SUB\fR socket, in which case a message shall be accepted if it matches at least one filter\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
binary data
T}
T{
.sp
Option value unit
T}:T{
.sp
N/A
T}
T{
.sp
Default value
T}:T{
.sp
N/A
T}
T{
.sp
Applicable socket types
T}:T{
.sp
ZMQ_SUB
T}
.TE
.sp 1
.SS "ZMQ_UNSUBSCRIBE: Remove message filter"
.sp
The \fIZMQ_UNSUBSCRIBE\fR option shall remove an existing message filter on a \fIZMQ_SUB\fR socket\&. The filter specified must match an existing filter previously established with the \fIZMQ_SUBSCRIBE\fR option\&. If the socket has several instances of the same filter attached the \fIZMQ_UNSUBSCRIBE\fR option shall remove only one instance, leaving the rest in place and functional\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
binary data
T}
T{
.sp
Option value unit
T}:T{
.sp
N/A
T}
T{
.sp
Default value
T}:T{
.sp
N/A
T}
T{
.sp
Applicable socket types
T}:T{
.sp
ZMQ_SUB
T}
.TE
.sp 1
.SS "ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN"
.sp
Sets the timeout for receive operation on the socket\&. If the value is 0, \fIzmq_recv(3)\fR 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\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int
T}
T{
.sp
Option value unit
T}:T{
.sp
milliseconds
T}
T{
.sp
Default value
T}:T{
.sp
\-1 (infinite)
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_SNDTIMEO: Maximum time before a send operation returns with EAGAIN"
.sp
Sets the timeout for send operation on the socket\&. If the value is 0, \fIzmq_send(3)\fR 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\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int
T}
T{
.sp
Option value unit
T}:T{
.sp
milliseconds
T}
T{
.sp
Default value
T}:T{
.sp
\-1 (infinite)
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_RATE: Set multicast data rate"
.sp
The \fIZMQ_RATE\fR option shall set the maximum send or receive data rate for multicast transports such as \fBzmq_pgm\fR(7) using the specified \fIsocket\fR\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
kilobits per second
T}
T{
.sp
Default value
T}:T{
.sp
100
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, when using multicast transports
T}
.TE
.sp 1
.SS "ZMQ_RECOVERY_IVL: Set multicast recovery interval"
.sp
The \fIZMQ_RECOVERY_IVL\fR option shall set the recovery interval for multicast transports using the specified \fIsocket\fR\&. The recovery interval determines the maximum time in seconds that a receiver can be absent from a multicast group before unrecoverable data loss will occur\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBCaution\fR
.ps -1
.br
.sp
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\&.
.sp .5v
.RE
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
seconds
T}
T{
.sp
Default value
T}:T{
.sp
10
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, when using multicast transports
T}
.TE
.sp 1
.SS "ZMQ_RECOVERY_IVL_MSEC: Set multicast recovery interval in milliseconds"
.sp
The \fIZMQ_RECOVERY_IVL_MSEC\fR option shall set the recovery interval, specified in milliseconds (ms) for multicast transports using the specified \fIsocket\fR\&. 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\&.
.sp
A non\-zero value of the \fIZMQ_RECOVERY_IVL_MSEC\fR option will take precedence over the \fIZMQ_RECOVERY_IVL\fR option, but since the default for the \fIZMQ_RECOVERY_IVL_MSEC\fR is \-1, the default is to use the \fIZMQ_RECOVERY_IVL\fR option value\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBCaution\fR
.ps -1
.br
.sp
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\&.
.sp .5v
.RE
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
milliseconds
T}
T{
.sp
Default value
T}:T{
.sp
\-1
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, when using multicast transports
T}
.TE
.sp 1
.SS "ZMQ_MCAST_LOOP: Control multicast loop\-back"
.sp
The \fIZMQ_MCAST_LOOP\fR option shall control whether data sent via multicast transports using the specified \fIsocket\fR can also be received by the sending host via loop\-back\&. A value of zero disables the loop\-back functionality, while the default value of 1 enables the loop\-back functionality\&. Leaving multicast loop\-back enabled when it is not required can have a negative impact on performance\&. Where possible, disable \fIZMQ_MCAST_LOOP\fR in production environments\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
boolean
T}
T{
.sp
Default value
T}:T{
.sp
1
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, when using multicast transports
T}
.TE
.sp 1
.SS "ZMQ_SNDBUF: Set kernel transmit buffer size"
.sp
The \fIZMQ_SNDBUF\fR option shall set the underlying kernel transmit buffer size for the \fIsocket\fR to the specified size in bytes\&. A value of zero means leave the OS default unchanged\&. For details please refer to your operating system documentation for the \fISO_SNDBUF\fR socket option\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
uint64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
bytes
T}
T{
.sp
Default value
T}:T{
.sp
0
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_RCVBUF: Set kernel receive buffer size"
.sp
The \fIZMQ_RCVBUF\fR option shall set the underlying kernel receive buffer size for the \fIsocket\fR to the specified size in bytes\&. A value of zero means leave the OS default unchanged\&. For details refer to your operating system documentation for the \fISO_RCVBUF\fR socket option\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
uint64_t
T}
T{
.sp
Option value unit
T}:T{
.sp
bytes
T}
T{
.sp
Default value
T}:T{
.sp
0
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all
T}
.TE
.sp 1
.SS "ZMQ_LINGER: Set linger period for socket shutdown"
.sp
The \fIZMQ_LINGER\fR option shall set the linger period for the specified \fIsocket\fR\&. 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 \fBzmq_close\fR(3), and further affects the termination of the socket\(cqs context with \fBzmq_term\fR(3)\&. The following outlines the different behaviours:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The default value of
\fI\-1\fR
specifies an infinite linger period\&. Pending messages shall not be discarded after a call to
\fIzmq_close()\fR; attempting to terminate the socket\(cqs context with
\fIzmq_term()\fR
shall block until all pending messages have been sent to a peer\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The value of
\fI0\fR
specifies no linger period\&. Pending messages shall be discarded immediately when the socket is closed with
\fIzmq_close()\fR\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Positive values specify an upper bound for the linger period in milliseconds\&. Pending messages shall not be discarded after a call to
\fIzmq_close()\fR; attempting to terminate the socket\(cqs context with
\fIzmq_term()\fR
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\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
Option value type
T}:T{
int
T}
T{
Option value unit
T}:T{
milliseconds
T}
T{
Default value
T}:T{
\-1 (infinite)
T}
T{
Applicable socket types
T}:T{
all
T}
.TE
.sp 1
.RE
.SS "ZMQ_RECONNECT_IVL: Set reconnection interval"
.sp
The \fIZMQ_RECONNECT_IVL\fR option shall set the initial reconnection interval for the specified \fIsocket\fR\&. The reconnection interval is the period 0MQ shall wait between attempts to reconnect disconnected peers when using connection\-oriented transports\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
.sp
The reconnection interval may be randomized by 0MQ to prevent reconnection storms in topologies with a large number of peers per socket\&.
.sp .5v
.RE
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int
T}
T{
.sp
Option value unit
T}:T{
.sp
milliseconds
T}
T{
.sp
Default value
T}:T{
.sp
100
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, only for connection\-oriented transports
T}
.TE
.sp 1
.SS "ZMQ_RECONNECT_IVL_MAX: Set maximum reconnection interval"
.sp
The \fIZMQ_RECONNECT_IVL_MAX\fR option shall set the maximum reconnection interval for the specified \fIsocket\fR\&. 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\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
.sp
Values less than ZMQ_RECONNECT_IVL will be ignored\&.
.sp .5v
.RE
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int
T}
T{
.sp
Option value unit
T}:T{
.sp
milliseconds
T}
T{
.sp
Default value
T}:T{
.sp
0 (only use ZMQ_RECONNECT_IVL)
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, only for connection\-oriented transports
T}
.TE
.sp 1
.SS "ZMQ_BACKLOG: Set maximum length of the queue of outstanding connections"
.sp
The \fIZMQ_BACKLOG\fR option shall set the maximum length of the queue of outstanding peer connections for the specified \fIsocket\fR; this only applies to connection\-oriented transports\&. For details refer to your operating system documentation for the \fIlisten\fR function\&.
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Option value type
T}:T{
.sp
int
T}
T{
.sp
Option value unit
T}:T{
.sp
connections
T}
T{
.sp
Default value
T}:T{
.sp
100
T}
T{
.sp
Applicable socket types
T}:T{
.sp
all, only for connection\-oriented transports\&.
T}
.TE
.sp 1
.SH "RETURN VALUE"
.sp
The \fIzmq_setsockopt()\fR function shall return zero if successful\&. Otherwise it shall return \-1 and set \fIerrno\fR to one of the values defined below\&.
.SH "ERRORS"
.PP
\fBEINVAL\fR
.RS 4
The requested option
\fIoption_name\fR
is unknown, or the requested
\fIoption_len\fR
or
\fIoption_value\fR
is invalid\&.
.RE
.PP
\fBETERM\fR
.RS 4
The 0MQ
\fIcontext\fR
associated with the specified
\fIsocket\fR
was terminated\&.
.RE
.PP
\fBENOTSOCK\fR
.RS 4
The provided
\fIsocket\fR
was invalid\&.
.RE
.PP
\fBEINTR\fR
.RS 4
The operation was interrupted by delivery of a signal\&.
.RE
.SH "EXAMPLE"
.PP
\fBSubscribing to messages on a ZMQ_SUB socket\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
/* Subscribe to all messages */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "", 0);
assert (rc == 0);
/* Subscribe to messages prefixed with "ANIMALS\&.CATS" */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "ANIMALS\&.CATS", 12);
.fi
.if n \{\
.RE
.\}
.PP
\fBSetting I/O thread affinity\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
int64_t affinity;
/* Incoming connections on TCP port 5555 shall be handled by I/O thread 1 */
affinity = 1;
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof affinity);
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 */
affinity = 2;
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof affinity);
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5556");
assert (rc);
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.sp
\fBzmq_getsockopt\fR(3) \fBzmq_socket\fR(3) \fBzmq\fR(7)
.SH "AUTHORS"
.sp
This manual page was written by the 0MQ community\&.