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authorMartin Lucina <martin@lucina.net>2012-01-23 08:53:19 +0100
committerMartin Lucina <martin@lucina.net>2012-01-23 08:53:19 +0100
commita15854bd92db69fcd0b4444fe1b8fe3610a7acf6 (patch)
tree1214b945d0f0033ff318de367c70525ea141ef56 /doc/zmq_getsockopt.3
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+'\" t
+.\" Title: zmq_getsockopt
+.\" Author: [see the "AUTHORS" section]
+.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
+.\" Date: 06/04/2010
+.\" Manual: 0MQ Manual
+.\" Source: 0MQ 2.0.7
+.\" Language: English
+.\"
+.TH "ZMQ_GETSOCKOPT" "3" "06/04/2010" "0MQ 2\&.0\&.7" "0MQ Manual"
+.\" -----------------------------------------------------------------
+.\" * Define some portability stuff
+.\" -----------------------------------------------------------------
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.\" http://bugs.debian.org/507673
+.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.\" -----------------------------------------------------------------
+.\" * set default formatting
+.\" -----------------------------------------------------------------
+.\" disable hyphenation
+.nh
+.\" disable justification (adjust text to left margin only)
+.ad l
+.\" -----------------------------------------------------------------
+.\" * MAIN CONTENT STARTS HERE *
+.\" -----------------------------------------------------------------
+.SH "NAME"
+zmq_getsockopt \- get 0MQ socket options
+.SH "SYNOPSIS"
+.sp
+\fBint zmq_getsockopt (void \fR\fB\fI*socket\fR\fR\fB, int \fR\fB\fIoption_name\fR\fR\fB, void \fR\fB\fI*option_value\fR\fR\fB, size_t \fR\fB\fI*option_len\fR\fR\fB);\fR
+.SH "DESCRIPTION"
+.sp
+The \fIzmq_getsockopt()\fR function shall retrieve the value for the option specified by the \fIoption_name\fR argument for the 0MQ socket pointed to by the \fIsocket\fR argument, and store it in the buffer pointed to by the \fIoption_value\fR argument\&. The \fIoption_len\fR argument is the size in bytes of the buffer pointed to by \fIoption_value\fR; upon successful completion \fIzmq_getsockopt()\fR shall modify the \fIoption_value\fR argument to indicate the actual size of the option value stored in the buffer\&.
+.sp
+The following options can be retrieved with the \fIzmq_getsockopt()\fR function:
+.SS "ZMQ_RCVMORE: More message parts to follow"
+.sp
+The \fIZMQ_RCVMORE\fR option shall return a boolean value indicating if the multi\-part message currently being read from the specified \fIsocket\fR has more message parts to follow\&. If there are no message parts to follow or if the message currently being read is not a multi\-part message a value of zero shall be returned\&. Otherwise, a value of 1 shall be returned\&.
+.sp
+Refer to \fBzmq_send\fR(3) and \fBzmq_recv\fR(3) for a detailed description of sending/receiving multi\-part messages\&.
+.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
+N/A
+T}
+T{
+.sp
+Applicable socket types
+T}:T{
+.sp
+all
+T}
+.TE
+.sp 1
+.SS "ZMQ_HWM: Retrieve high water mark"
+.sp
+The \fIZMQ_HWM\fR option shall retrieve 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
+int64_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: Retrieve disk offload size"
+.sp
+The \fIZMQ_SWAP\fR option shall retrieve 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 it\(cqs 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: Retrieve I/O thread affinity"
+.sp
+The \fIZMQ_AFFINITY\fR option shall retrieve 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
+int64_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: Retrieve socket identity"
+.sp
+The \fIZMQ_IDENTITY\fR option shall retrieve the identity of the specified \fIsocket\fR\&. Socket identity determines if existing 0MQ infastructure (\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 can 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_RATE: Retrieve multicast data rate"
+.sp
+The \fIZMQ_RATE\fR option shall retrieve the maximum send or receive data rate for multicast transports using the specified \fIsocket\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
+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: Get multicast recovery interval"
+.sp
+The \fIZMQ_RECOVERY_IVL\fR option shall retrieve 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\&.
+.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
+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_MCAST_LOOP: Control multicast loopback"
+.sp
+The \fIZMQ_MCAST_LOOP\fR option controls whether data sent via multicast transports can also be received by the sending host via loopback\&. A value of zero indicates that the loopback functionality is disabled, while the default value of 1 indicates that the loopback functionality is enabled\&. Leaving multicast loopback 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
+uint64_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: Retrieve kernel transmit buffer size"
+.sp
+The \fIZMQ_SNDBUF\fR option shall retrieve the underlying kernel transmit buffer size for the specified \fIsocket\fR\&. A value of zero means that the OS default is in effect\&. For details 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: Retrieve kernel receive buffer size"
+.sp
+The \fIZMQ_RCVBUF\fR option shall retrieve the underlying kernel receive buffer size for the specified \fIsocket\fR\&. A value of zero means that the OS default is in effect\&. 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
+.SH "RETURN VALUE"
+.sp
+The \fIzmq_getsockopt()\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, or the size of the buffer pointed to by
+\fIoption_value\fR, as specified by
+\fIoption_len\fR, is insufficient for storing the option value\&.
+.RE
+.PP
+\fBETERM\fR
+.RS 4
+The 0MQ
+\fIcontext\fR
+associated with the specified
+\fIsocket\fR
+was terminated\&.
+.RE
+.SH "EXAMPLE"
+.PP
+\fBRetrieving the high water mark\fR.
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+/* Retrieve high water mark into hwm */
+int64_t hwm;
+rc = zmq_getsockopt (socket, ZMQ_HWM, &hwm, sizeof hwm);
+assert (rc == 0);
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+.SH "SEE ALSO"
+.sp
+\fBzmq_setsockopt\fR(3) \fBzmq_socket\fR(3) \fBzmq\fR(7)
+.SH "AUTHORS"
+.sp
+The 0MQ documentation was written by Martin Sustrik <\m[blue]\fBsustrik@250bpm\&.com\fR\m[]\&\s-2\u[1]\d\s+2> and Martin Lucina <\m[blue]\fBmato@kotelna\&.sk\fR\m[]\&\s-2\u[2]\d\s+2>\&.
+.SH "NOTES"
+.IP " 1." 4
+sustrik@250bpm.com
+.RS 4
+\%mailto:sustrik@250bpm.com
+.RE
+.IP " 2." 4
+mato@kotelna.sk
+.RS 4
+\%mailto:mato@kotelna.sk
+.RE