zmq_setsockopt(3)

SYNOPSIS

int zmq_setsockopt (void *socket, int option_name, const void *option_value, size_t option_len);

DESCRIPTION

The zmq_setsockopt() function shall set the option specified by the +option_name argument to the value pointed to by the option_value argument +for the ØMQ socket pointed to by the socket argument. The option_len +argument is the size of the option value in bytes.

The following socket options can be set with the zmq_setsockopt() function:

ZMQ_HWM: Set high water mark

The ZMQ_HWM option shall set the high water mark for the specified socket. +The high water mark is a hard limit on the maximum number of outstanding +messages ØMQ shall queue in memory for any single peer that the specified +socket is communicating with.

If this limit has been reached the socket shall enter an exceptional state and +depending on the socket type, ØMQ shall take appropriate action such as +blocking or dropping sent messages. Refer to the individual socket descriptions +in zmq_socket(3) for details on the exact action taken for each socket +type.

The default ZMQ_HWM value of zero means "no limit".

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +int64_t + +
+Option value unit + +	+ +messages + +
+Default value + +	+ +0 + +
+Applicable socket types + +	+ +all + +

ZMQ_SWAP: Set disk offload size

The ZMQ_SWAP option shall set the disk offload (swap) size for the specified +socket. A socket which has ZMQ_SWAP set to a non-zero value may exceed it’s +high water mark; in this case outstanding messages shall be offloaded to +storage on disk rather than held in memory.

The value of ZMQ_SWAP defines the maximum size of the swap space in bytes.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +int64_t + +
+Option value unit + +	+ +bytes + +
+Default value + +	+ +0 + +
+Applicable socket types + +	+ +all + +

ZMQ_AFFINITY: Set I/O thread affinity

The ZMQ_AFFINITY option shall set the I/O thread affinity for newly created +connections on the specified socket.

Affinity determines which threads from the ØMQ 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 +ØMQ 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 zmq_init(3) for details on allocating the number of I/O +threads for a specific context.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +int64_t + +
+Option value unit + +	+ +N/A (bitmap) + +
+Default value + +	+ +0 + +
+Applicable socket types + +	+ +N/A + +

ZMQ_IDENTITY: Set socket identity

The ZMQ_IDENTITY option shall set the identity of the specified socket. +Socket identity determines if existing ØMQ infastructure (message queues, +forwarding devices) shall be identified with a specific application and +persist across multiple runs of the application.

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 ØMQ infrastructure configured by the previous run(s). Thus the +application may receive messages that were sent in the meantime, message +queue limits shall be shared with previous run(s) and so on.

Identity should be at least one byte and at most 255 bytes long. Identities +starting with binary zero are reserved for use by ØMQ infrastructure.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +binary data + +
+Option value unit + +	+ +N/A + +
+Default value + +	+ +NULL + +
+Applicable socket types + +	+ +all + +

ZMQ_SUBSCRIBE: Establish message filter

The ZMQ_SUBSCRIBE option shall establish a new message filter on a ZMQ_SUB +socket. Newly created ZMQ_SUB sockets shall filter out all incoming messages, +therefore you should call this option to establish an initial message filter.

An empty option_value of length zero shall subscribe to all incoming +messages. A non-empty option_value shall subscribe to all messages beginning +with the specified prefix. Mutiple filters may be attached to a single +ZMQ_SUB socket, in which case a message shall be accepted if it matches at +least one filter.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +binary data + +
+Option value unit + +	+ +N/A + +
+Default value + +	+ +N/A + +
+Applicable socket types + +	+ +ZMQ_SUB + +

ZMQ_UNSUBSCRIBE: Remove message filter

The ZMQ_UNSUBSCRIBE option shall remove an existing message filter on a +ZMQ_SUB socket. The filter specified must match an existing filter previously +established with the ZMQ_SUBSCRIBE option. If the socket has several +instances of the same filter attached the ZMQ_UNSUBSCRIBE option shall remove +only one instance, leaving the rest in place and functional.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +binary data + +
+Option value unit + +	+ +N/A + +
+Default value + +	+ +N/A + +
+Applicable socket types + +	+ +ZMQ_SUB + +

ZMQ_RATE: Set multicast data rate

The ZMQ_RATE option shall set the maximum send or receive data rate for +multicast transports such as zmq_pgm(7) using the specified socket.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +uint64_t + +
+Option value unit + +	+ +kilobits per second + +
+Default value + +	+ +100 + +
+Applicable socket types + +	+ +all, when using multicast transports + +

ZMQ_RECOVERY_IVL: Set multicast recovery interval

The ZMQ_RECOVERY_IVL option shall set the recovery interval for multicast +transports using the specified socket. The recovery interval determines the +maximum time in seconds that a receiver can be absent from a multicast group +before unrecoverable data loss will occur.

+ + + +

Caution

Excersize 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.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +uint64_t + +
+Option value unit + +	+ +seconds + +
+Default value + +	+ +10 + +
+Applicable socket types + +	+ +all, when using multicast transports + +

ZMQ_MCAST_LOOP: Control multicast loopback

The ZMQ_MCAST_LOOP option shall control whether data sent via multicast +transports using the specified socket can also be received by the sending +host via loopback. A value of zero disables the loopback functionality, while +the default value of 1 enables the loopback functionality. Leaving multicast +loopback enabled when it is not required can have a negative impact on +performance. Where possible, disable ZMQ_MCAST_LOOP in production +environments.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +uint64_t + +
+Option value unit + +	+ +boolean + +
+Default value + +	+ +1 + +
+Applicable socket types + +	+ +all, when using multicast transports + +

ZMQ_SNDBUF: Set kernel transmit buffer size

The ZMQ_SNDBUF option shall set the underlying kernel transmit buffer size +for the socket 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 SO_SNDBUF socket option.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +uint64_t + +
+Option value unit + +	+ +bytes + +
+Default value + +	+ +0 + +
+Applicable socket types + +	+ +all + +

ZMQ_RCVBUF: Set kernel receive buffer size

The ZMQ_RCVBUF option shall set the underlying kernel receive buffer size for +the socket 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 SO_RCVBUF socket option.

+ + + + + + + + + + + + + + + + +

+Option value type + +	+ +uint64_t + +
+Option value unit + +	+ +bytes + +
+Default value + +	+ +0 + +
+Applicable socket types + +	+ +all + +

RETURN VALUE

The zmq_setsockopt() 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. +
+
+ETERM +: +
+The ØMQ context associated with the specified socket was terminated. +
+

EXAMPLE

Subscribing to messages on a ZMQ_SUB socket

/* 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);

Setting I/O thread affinity

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);

AUTHORS

The ØMQ documentation was written by Martin Sustrik <sustrik@250bpm.com> and +Martin Lucina <mato@kotelna.sk>.

+zmq_setsockopt(3) Manual Page +

NAME

SYNOPSIS

DESCRIPTION

ZMQ_HWM: Set high water mark

ZMQ_SWAP: Set disk offload size

ZMQ_AFFINITY: Set I/O thread affinity

ZMQ_IDENTITY: Set socket identity

ZMQ_SUBSCRIBE: Establish message filter

ZMQ_UNSUBSCRIBE: Remove message filter

ZMQ_RATE: Set multicast data rate

ZMQ_RECOVERY_IVL: Set multicast recovery interval

ZMQ_MCAST_LOOP: Control multicast loopback

ZMQ_SNDBUF: Set kernel transmit buffer size

ZMQ_RCVBUF: Set kernel receive buffer size

RETURN VALUE

ERRORS

EXAMPLE

SEE ALSO

AUTHORS