NAME

zmq_setsockopt - set 0MQ socket options

SYNOPSIS

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

Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE, ZMQ_LINGER, ZMQ_ROUTER_HANDOVER, ZMQ_ROUTER_MANDATORY, ZMQ_PROBE_ROUTER, ZMQ_XPUB_VERBOSE, ZMQ_XPUB_VERBOSER, ZMQ_REQ_CORRELATE, ZMQ_REQ_RELAXED, ZMQ_SNDHWM and ZMQ_RCVHWM, only take effect for subsequent socket bind/connects.

Specifically, security options take effect for subsequent bind/connect calls, and can be changed at any time to affect subsequent binds and/or connects.

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 0MQ socket pointed to by the 'socket' argument. The 'option_len' argument is the size of the option value in bytes. For options taking a value of type "character string", the provided byte data should either contain no zero bytes, or end in a single zero byte (terminating ASCII NUL character).

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

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 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 zmq_init for details on allocating the number of I/O threads for a specific context.

Option value type

uint64_t

Option value unit

N/A (bitmap)

Default value

0

Applicable socket types

N/A

ZMQ_BACKLOG: Set maximum length of the queue of outstanding connections

The 'ZMQ_BACKLOG' option shall set 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.

Option value type

int

Option value unit

connections

Default value

100

Applicable socket types

all, only for connection-oriented transports.

ZMQ_BINDTODEVICE: Set name of device to bind the socket to

The 'ZMQ_BINDTODEVICE' option binds this socket to a particular device, eg. an interface or VRF. If a socket is bound to an interface, only packets received from that particular 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.

Note
requires setting CAP_NET_RAW on the compiled program.
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_BUSY_POLL: This removes delays caused by the interrupt and the resultant context switch.

Busy polling helps reduce latency in the network receive path by allowing socket layer code to poll the receive queue of a network device, and disabling network interrupts. This removes delays caused by the interrupt and the resultant context switch. However, it also increases CPU utilization. Busy polling also prevents the CPU from sleeping, which can incur additional power consumption.

Option value type

int

Option value unit

0,1

Default value

0

Applicable socket types

all

ZMQ_CONNECT_RID: Assign the next outbound connection id

This option name is now deprecated. Use ZMQ_CONNECT_ROUTING_ID instead. ZMQ_CONNECT_RID remains as an alias for now.

ZMQ_CONNECT_ROUTING_ID: Assign the next outbound routing id

The 'ZMQ_CONNECT_ROUTING_ID' option sets the peer id of the peer connected via the next zmq_connect() call, such that that connection is immediately ready for data transfer with the given routing id. This option applies only to the first subsequent call to zmq_connect(), zmq_connect() calls thereafter use the default connection behaviour.

Typical use is to set this socket option ahead of each zmq_connect() call. Each connection MUST be assigned a unique routing id. Assigning a routing id that is already in use is not allowed.

Useful when connecting ROUTER to ROUTER, or STREAM to STREAM, as it allows for immediate sending to peers. Outbound routing id framing requirements for ROUTER and STREAM sockets apply.

The routing id must be from 1 to 255 bytes long and MAY NOT start with a zero byte (such routing ids are reserved for internal use by the 0MQ infrastructure).

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_ROUTER, ZMQ_STREAM

ZMQ_CONFLATE: Keep only last message

If set, a socket shall keep only one message in its inbound/outbound queue, this message being the last message received/the last message to be sent. Ignores 'ZMQ_RCVHWM' and 'ZMQ_SNDHWM' options. Does not support multi-part messages, in particular, only one part of it is kept in the socket internal queue.

Note
If recv is not called on the inbound socket, the queue and memory will grow with each message received. Use zmq_getsockopt with ZMQ_EVENTS to trigger the conflation of the messages.
Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

ZMQ_PULL, ZMQ_PUSH, ZMQ_SUB, ZMQ_PUB, ZMQ_DEALER

ZMQ_CONNECT_TIMEOUT: Set connect() timeout

Sets 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.

Option value type

int

Option value unit

milliseconds

Default value

0 (disabled)

Applicable socket types

all, when using TCP transports.

ZMQ_CURVE_PUBLICKEY: Set CURVE public key

Sets the socket’s long term public key. You must set this on CURVE client sockets, see zmq_curve You can provide the key as 32 binary bytes, or as a 40-character string encoded in the Z85 encoding format and terminated in a null byte. The public key must always be used with the matching secret key. To generate a public/secret key pair, use zmq_curve_keypair To derive the public key from a secret key, use zmq_curve_public

Note
an option value size of 40 is supported for backwards compatibility, though is deprecated.
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: Set CURVE secret key

Sets the socket’s long term secret key. You must set this on both CURVE client and server sockets, see zmq_curve You can provide the key as 32 binary bytes, or as a 40-character string encoded in the Z85 encoding format and terminated in a null byte. To generate a public/secret key pair, use zmq_curve_keypair To derive the public key from a secret key, use zmq_curve_public

Note
an option value size of 40 is supported for backwards compatibility, though is deprecated.
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_SERVER: Set CURVE server role

Defines whether the socket will act as server for CURVE security, see zmq_curve A value of '1' means the socket will act as CURVE server. A value of '0' means the socket will not act as CURVE server, and its security role then depends on other option settings. Setting this to '0' shall reset the socket security to NULL. When you set this you must also set the server’s secret key using the ZMQ_CURVE_SECRETKEY option. A server socket does not need to know its own public key.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

all, when using TCP transport

ZMQ_CURVE_SERVERKEY: Set CURVE server key

Sets the socket’s long term server key. You must set this on CURVE client sockets, see zmq_curve You can provide the key as 32 binary bytes, or as a 40-character string encoded in the Z85 encoding format and terminated in a null byte. This key must have been generated together with the server’s secret key. To generate a public/secret key pair, use zmq_curve_keypair

Note
an option value size of 40 is supported for backwards compatibility, though is deprecated.
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_DISCONNECT_MSG: set a disconnect message that the socket will generate when accepted peer disconnect

When set, the socket will generate a disconnect message when accepted peer has been disconnected. You may set this on ROUTER, SERVER and PEER sockets. The combination with ZMQ_HEARTBEAT_IVL is powerful and simplify protocols, when heartbeat recognize a connection drop it will generate a disconnect message that can match the protocol of the application.

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_ROUTER, ZMQ_SERVER and ZMQ_PEER

ZMQ_HICCUP_MSG: set a hiccup message that the socket will generate when connected peer temporarily disconnect

When set, the socket will generate a hiccup message when connect peer has been disconnected. You may set this on DEALER, CLIENT and PEER sockets. The combination with ZMQ_HEARTBEAT_IVL is powerful and simplify protocols, when heartbeat recognize a connection drop it will generate a hiccup message that can match the protocol of the application.

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_DEALER, ZMQ_CLIENT and ZMQ_PEER

ZMQ_GSSAPI_PLAINTEXT: Disable GSSAPI encryption

Defines whether communications on the socket will be encrypted, see zmq_gssapi A value of '1' means that communications will be plaintext. A value of '0' means communications will be encrypted.

Option value type

int

Option value unit

0, 1

Default value

0 (false)

Applicable socket types

all, when using TCP transport

ZMQ_GSSAPI_PRINCIPAL: Set name of GSSAPI principal

Sets the name of the principal for whom GSSAPI credentials should be acquired.

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_GSSAPI_SERVER: Set GSSAPI server role

Defines whether the socket will act as server for GSSAPI security, see zmq_gssapi A value of '1' means the socket will act as GSSAPI server. A value of '0' means the socket will act as GSSAPI client.

Option value type

int

Option value unit

0, 1

Default value

0 (false)

Applicable socket types

all, when using TCP transport

ZMQ_GSSAPI_SERVICE_PRINCIPAL: Set name of GSSAPI service principal

Sets the name of the principal of the GSSAPI server to which a GSSAPI client intends to connect.

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE: Set name type of service principal

Sets the name type of the GSSAPI service principal. 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).

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 transport

ZMQ_GSSAPI_PRINCIPAL_NAMETYPE: Set name type of principal

Sets the name type of the GSSAPI principal. 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).

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 transport

ZMQ_HANDSHAKE_IVL: Set maximum handshake interval

The 'ZMQ_HANDSHAKE_IVL' option shall set 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.

Option value type

int

Option value unit

milliseconds

Default value

30000

Applicable socket types

all but ZMQ_STREAM, only for connection-oriented transports

ZMQ_HELLO_MSG: set an hello message that will be sent when a new peer connect

When set, the socket will automatically send an hello message when a new connection is made or accepted. You may set this on DEALER, ROUTER, CLIENT, SERVER and PEER sockets. The combination with ZMQ_HEARTBEAT_IVL is powerful and simplify protocols, as now heartbeat and sending the hello message can be left out of protocols and be handled by zeromq.

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_ROUTER, ZMQ_DEALER, ZMQ_CLIENT, ZMQ_SERVER and ZMQ_PEER

ZMQ_HEARTBEAT_IVL: Set interval between sending ZMTP heartbeats

The 'ZMQ_HEARTBEAT_IVL' option shall set the interval between sending ZMTP heartbeats for the specified 'socket'. If this option is set and is greater than 0, then a 'PING' ZMTP command will be sent every 'ZMQ_HEARTBEAT_IVL' milliseconds.

Option value type

int

Option value unit

milliseconds

Default value

0

Applicable socket types

all, when using connection-oriented transports

ZMQ_HEARTBEAT_TIMEOUT: Set timeout for ZMTP heartbeats

The 'ZMQ_HEARTBEAT_TIMEOUT' option shall set how long to wait before timing-out a connection after sending a 'PING' ZMTP command and not receiving any traffic. This option is only valid if 'ZMQ_HEARTBEAT_IVL' is also set, and is greater than 0. The connection will time out if there is no traffic received after sending the 'PING' command, but the received traffic does not have to be a 'PONG' command - any received traffic will cancel the timeout.

Option value type

int

Option value unit

milliseconds

Default value

0 normally, ZMQ_HEARTBEAT_IVL if it is set

Applicable socket types

all, when using connection-oriented transports

ZMQ_HEARTBEAT_TTL: Set the TTL value for ZMTP heartbeats

The 'ZMQ_HEARTBEAT_TTL' option shall set the timeout on the remote peer for ZMTP heartbeats. If this option is greater than 0, the remote side shall time out the connection if it does not receive any more traffic within the TTL period. This option does not have any effect if 'ZMQ_HEARTBEAT_IVL' is not set or is 0. Internally, this value is rounded down to the nearest decisecond, any value less than 100 will have no effect.

Option value type

int

Option value unit

milliseconds

Default value

0

Maximum value

6553599 (which is 2^16-1 deciseconds)

Applicable socket types

all, when using connection-oriented transports

ZMQ_IDENTITY: Set socket identity

This option name is now deprecated. Use ZMQ_ROUTING_ID instead. ZMQ_IDENTITY remains as an alias for now.

ZMQ_IMMEDIATE: Queue messages only to completed connections

By default queues will fill on outgoing connections even if the connection has not completed. This can lead to "lost" messages on sockets with round-robin routing (REQ, PUSH, DEALER). If this option is set to 1, messages shall be queued only to completed connections. This will cause the socket to block if there are no other connections, but will prevent queues from filling on pipes awaiting connection.

Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

all, only for connection-oriented transports.

ZMQ_INVERT_MATCHING: Invert message filtering

Reverses the filtering behavior of PUB-SUB sockets, when set to 1.

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.

Option value type

int

Option value unit

0,1

Default value

0

Applicable socket types

ZMQ_PUB, ZMQ_XPUB, ZMQ_SUB

ZMQ_IPV6: Enable IPv6 on socket

Set 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.

Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

all, when using TCP transports.

ZMQ_LINGER: Set linger period for socket shutdown

The 'ZMQ_LINGER' option shall set 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 disconnected with zmq_disconnect or closed with zmq_close, and further affects the termination of the socket’s context with zmq_ctx_term The following outlines the different behaviours:

  • A value of '-1' specifies an infinite linger period. Pending messages shall not be discarded after a call to zmq_disconnect() or 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 after a call to zmq_disconnect() or 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_disconnect() or 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.

Option value type

int

Option value unit

milliseconds

Default value

-1 (infinite)

Applicable socket types

all

ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size

Limits the size of the inbound message. If a peer sends a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means 'no limit'.

Option value type

int64_t

Option value unit

bytes

Default value

-1

Applicable socket types

all

ZMQ_METADATA: Add application metadata properties to a socket

The ZMQ_METADATA option shall add application metadata to the specified socket, the metadata is exchanged with peers during connection setup. A metadata property is specified as a string, delimited by a colon, starting with the metadata property followed by the metadata value, for example "X-key:value". Property names are restricted to maximum 255 characters and must be prefixed by "X-". Multiple application metadata properties can be added to a socket by executing zmq_setsockopt() multiple times. As the argument is a null-terminated string, binary data must be encoded before it is added e.g. using Z85 (zmq_z85_encode).

Note
in DRAFT state, not yet available in stable releases.
Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all

ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets

Sets the time-to-live field in every multicast packet sent from this socket. The default is 1 which means that the multicast packets don’t leave the local network.

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

Sets 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.

Option value type

int

Option value unit

bytes

Default value

1500

Applicable socket types

all, when using multicast transports

ZMQ_PLAIN_PASSWORD: Set PLAIN security password

Sets the password for outgoing connections over TCP or IPC. If you set this to a non-null value, the security mechanism used for connections shall be PLAIN, see zmq_plain If you set this to a null value, the security mechanism used for connections shall be NULL, see zmq_null

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_PLAIN_SERVER: Set PLAIN server role

Defines whether the socket will act as server for PLAIN security, see zmq_plain A value of '1' means the socket will act as PLAIN server. A value of '0' means the socket will not act as PLAIN server, and its security role then depends on other option settings. Setting this to '0' shall reset the socket security to NULL.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

all, when using TCP transport

ZMQ_PLAIN_USERNAME: Set PLAIN security username

Sets the username for outgoing connections over TCP or IPC. If you set this to a non-null value, the security mechanism used for connections shall be PLAIN, see zmq_plain If you set this to a null value, the security mechanism used for connections shall be NULL, see zmq_null

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_USE_FD: Set the pre-allocated socket file descriptor

When set to a positive integer value before zmq_bind is called on the socket, the socket shall use the corresponding file descriptor for connections over TCP or IPC instead of allocating a new file descriptor. Useful for writing systemd socket activated services. If set to -1 (default), a new file descriptor will be allocated instead (default behaviour).

Note
if set after calling zmq_bind, this option shall have no effect. NOTE: the file descriptor passed through MUST have been ran through the "bind" and "listen" system calls beforehand. Also, socket option that would normally be passed through zmq_setsockopt like TCP buffers length, IP_TOS or SO_REUSEADDR MUST be set beforehand by the caller, as they must be set before the socket is bound.
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_PRIORITY: Set the Priority on socket

Sets the protocol-defined priority for all packets to be sent on this socket, where supported by the OS. In Linux, values greater than 6 require admin capability (CAP_NET_ADMIN)

Option value type

int

Option value unit

>0

Default value

0

Applicable socket types

all, only for connection-oriented transports

ZMQ_PROBE_ROUTER: bootstrap connections to ROUTER sockets

When set to 1, the socket will automatically send an empty message when a new connection is made or accepted. You may set this on REQ, DEALER, or ROUTER sockets connected to a ROUTER socket. The application must filter such empty messages. The ZMQ_PROBE_ROUTER option in effect provides the ROUTER application with an event signaling the arrival of a new peer.

Note
do not set this option on a socket that talks to any other socket types: the results are undefined.
Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_ROUTER, ZMQ_DEALER, ZMQ_REQ

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 using the specified 'socket'.

Option value type

int

Option value unit

kilobits per second

Default value

100

Applicable socket types

all, when using multicast transports

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 -1 means leave the OS default unchanged. For details refer to your operating system documentation for the 'SO_RCVBUF' socket option.

Option value type

int

Option value unit

bytes

Default value

-1

Applicable socket types

all

ZMQ_RCVHWM: Set high water mark for inbound messages

The 'ZMQ_RCVHWM' option shall set 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 zmq_socket for details on the exact action taken for each socket type.

Note
0MQ does not guarantee that the socket will be able to queue as many as ZMQ_RCVHWM messages, and the actual limit may be lower or higher, depending on socket transport. A notable example is for sockets using TCP transport; see zmq_tcp
Option value type

int

Option value unit

messages

Default value

1000

Applicable socket types

all

ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN

Sets the timeout for receive 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.

Option value type

int

Option value unit

milliseconds

Default value

-1 (infinite)

Applicable socket types

all

ZMQ_RECONNECT_IVL: Set reconnection interval

The 'ZMQ_RECONNECT_IVL' option shall set 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.
Option value type

int

Option value unit

milliseconds

Default value

100

Applicable socket types

all, only for connection-oriented transports

ZMQ_RECONNECT_IVL_MAX: Set max reconnection interval

The 'ZMQ_RECONNECT_IVL_MAX' option shall set the max reconnection interval for the specified 'socket'. 0MQ shall wait at most the configured interval between reconnection attempts. The interval grows exponentionally (i.e.: it is doubled) with each attempt until it reaches ZMQ_RECONNECT_IVL_MAX. Default value means that the reconnect interval is based exclusively on ZMQ_RECONNECT_IVL and no exponential backoff is performed.

Note
Value has to be greater or equal than ZMQ_RECONNECT_IVL, or else it will be ignored.
Option value type

int

Option value unit

milliseconds

Default value

0 (ZMQ_RECONNECT_IVL will be used)

Applicable socket types

all, only for connection-oriented transports

ZMQ_RECONNECT_STOP: Set condition where reconnection will stop

The 'ZMQ_RECONNECT_STOP' option shall set the conditions under which automatic reconnection will stop. This can be useful when a process binds to a wild-card port, where the OS supplies an ephemeral port.

The 'ZMQ_RECONNECT_STOP_CONN_REFUSED' option will stop reconnection when 0MQ receives the ECONNREFUSED return code from the connect. This indicates that there is no code bound to the specified endpoint.

The 'ZMQ_RECONNECT_STOP_HANDSHAKE_FAILED' option will stop reconnection if the 0MQ handshake fails. This can be used to detect and/or prevent errant connection attempts to non-0MQ sockets. Note that when specifying this option you may also want to set ZMQ_HANDSHAKE_IVL — the default handshake interval is 30000 (30 seconds), which is typically too large.

The 'ZMQ_RECONNECT_STOP_AFTER_DISCONNECT' option will stop reconnection when zmq_disconnect() has been called. This can be useful when the user’s request failed (server not ready), as the socket does not need to continue to reconnect after user disconnect actively.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

0, ZMQ_RECONNECT_STOP_CONN_REFUSED, ZMQ_RECONNECT_STOP_HANDSHAKE_FAILED, ZMQ_RECONNECT_STOP_CONN_REFUSED | ZMQ_RECONNECT_STOP_HANDSHAKE_FAILED

Default value

0

Applicable socket types

all, only for connection-oriented transports (ZMQ_HANDSHAKE_IVL is not applicable for ZMQ_STREAM sockets)

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 milliseconds that a receiver can be absent from a multicast group before unrecoverable data loss will occur.

Caution
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.
Option value type

int

Option value unit

milliseconds

Default value

10000

Applicable socket types

all, when using multicast transports

ZMQ_REQ_CORRELATE: match replies with requests

The default behaviour of REQ sockets is to rely on the ordering of messages to match requests and responses and that is usually sufficient. When this option is set to 1, the REQ socket will prefix outgoing messages with an extra frame containing a request id. That means the full message is (request id, 0, user frames…​). The REQ socket will discard all incoming messages that don’t begin with these two frames.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_REQ

ZMQ_REQ_RELAXED: relax strict alternation between request and reply

By default, a REQ socket does not allow initiating a new request with zmq_send(3) until the reply to the previous one has been received. When set to 1, sending another message is allowed and previous replies will be discarded if any. The request-reply state machine is reset and a new request is sent to the next available peer.

If set to 1, also enable ZMQ_REQ_CORRELATE to ensure correct matching of requests and replies. Otherwise a late reply to an aborted request can be reported as the reply to the superseding request.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_REQ

ZMQ_ROUTER_HANDOVER: handle duplicate client routing ids on ROUTER sockets

If two clients use the same routing id when connecting to a ROUTER, the results shall depend on the ZMQ_ROUTER_HANDOVER option setting. If that is not set (or set to the default of zero), the ROUTER socket shall reject clients trying to connect with an already-used routing id. If that option is set to 1, the ROUTER socket shall hand-over the connection to the new client and disconnect the existing one.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_ROUTER

ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER sockets

Sets the ROUTER socket behaviour when an unroutable message is encountered. A value of 0 is the default and discards the message silently when it cannot be routed or the peers SNDHWM is reached. A value of 1 returns an 'EHOSTUNREACH' error code if the message cannot be routed or 'EAGAIN' error code if the SNDHWM is reached and ZMQ_DONTWAIT was used. Without ZMQ_DONTWAIT it will block until the SNDTIMEO is reached or a spot in the send queue opens up.

When ZMQ_ROUTER_MANDATORY is set to 1, 'ZMQ_POLLOUT' events will be generated if one or more messages can be sent to at least one of the peers. If ZMQ_ROUTER_MANDATORY is set to 0, the socket will generate a 'ZMQ_POLLOUT' event on every call to 'zmq_poll' resp. 'zmq_poller_wait_all'.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_ROUTER

ZMQ_ROUTER_RAW: switch ROUTER socket to raw mode

Sets the raw mode on the ROUTER, when set to 1. When the ROUTER socket is in raw mode, and when using the tcp:// transport, it will read and write TCP data without 0MQ framing. This lets 0MQ applications talk to non-0MQ applications. When using raw mode, you cannot set explicit identities, and the ZMQ_SNDMORE flag is ignored when sending data messages. In raw mode you can close a specific connection by sending it a zero-length message (following the routing id frame).

Note
This option is deprecated, please use ZMQ_STREAM sockets instead.
Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_ROUTER

ZMQ_ROUTING_ID: Set socket routing id

The 'ZMQ_ROUTING_ID' option shall set the routing id of the specified 'socket' when connecting to a ROUTER socket.

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.

If two clients use the same routing id when connecting to a ROUTER, the results shall depend on the ZMQ_ROUTER_HANDOVER option setting. If that is not set (or set to the default of zero), the ROUTER socket shall reject clients trying to connect with an already-used routing id. If that option is set to 1, the ROUTER socket shall hand-over the connection to the new client and disconnect the existing one.

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_REQ, ZMQ_REP, ZMQ_ROUTER, ZMQ_DEALER.

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 -1 means leave the OS default unchanged. For details please refer to your operating system documentation for the 'SO_SNDBUF' socket option.

Option value type

int

Option value unit

bytes

Default value

-1

Applicable socket types

all

ZMQ_SNDHWM: Set high water mark for outbound messages

The 'ZMQ_SNDHWM' option shall set 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 zmq_socket for details on the exact action taken for each socket type.

Note
0MQ does not guarantee that the socket will accept as many as ZMQ_SNDHWM messages, and the actual limit may be as much as 90% lower depending on the flow of messages on the socket. The socket may even be able to accept more messages than the ZMQ_SNDHWM threshold; a notable example is for sockets using TCP transport; see zmq_tcp
Option value type

int

Option value unit

messages

Default value

1000

Applicable socket types

all

ZMQ_SNDTIMEO: Maximum time before a send operation returns with EAGAIN

Sets 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.

Option value type

int

Option value unit

milliseconds

Default value

-1 (infinite)

Applicable socket types

all

ZMQ_SOCKS_PROXY: Set SOCKS5 proxy address

Sets the SOCKS5 proxy address that shall be used by the socket for the TCP connection(s). Supported authentication methods are: no authentication or basic authentication when setup with ZMQ_SOCKS_USERNAME. If the endpoints are domain names instead of addresses they shall not be resolved and they shall be forwarded unchanged to the SOCKS proxy service in the client connection request message (address type 0x03 domain name).

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_SOCKS_USERNAME: Set SOCKS username and select basic authentication

Sets the username for authenticated connection to the SOCKS5 proxy. If you set this to a non-null and non-empty value, the authentication method used for the SOCKS5 connection shall be basic authentication. In this case, use ZMQ_SOCKS_PASSWORD option in order to set the password. If you set this to a null value or empty value, the authentication method shall be no authentication, the default.

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_SOCKS_PASSWORD: Set SOCKS basic authentication password

Sets the password for authenticating to the SOCKS5 proxy server. This is used only when the SOCKS5 authentication method has been set to basic authentication through the ZMQ_SOCKS_USERNAME option. Setting this to a null value (the default) is equivalent to an empty password string.

Option value type

character string

Option value unit

N/A

Default value

not set

Applicable socket types

all, when using TCP transport

ZMQ_STREAM_NOTIFY: send connect and disconnect notifications

Enables connect and disconnect notifications on a STREAM socket, when set to 1. When notifications are enabled, the socket delivers a zero-length message when a peer connects or disconnects.

Option value type

int

Option value unit

0, 1

Default value

1

Applicable socket types

ZMQ_STREAM

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. Multiple 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_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.

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.

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.

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.

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: Set TCP Maximum Retransmit Timeout

On OSes where it is supported, sets 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.

Option value type

int

Option value unit

milliseconds

Default value

0 (leave to OS default)

Applicable socket types

all, when using TCP transports.

ZMQ_TOS: Set the Type-of-Service on socket

Sets the ToS fields (Differentiated services (DS) and Explicit Congestion Notification (ECN) field of the IP header. The ToS field is typically used to specify a packets priority. The availability of this option is dependent on intermediate network equipment that inspect the ToS field and provide a path for low-delay, high-throughput, highly-reliable service, etc.

Option value type

int

Option value unit

>0

Default value

0

Applicable socket types

all, only for connection-oriented transports

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_XPUB_VERBOSE: pass duplicate subscribe messages on XPUB socket

Sets the 'XPUB' socket behaviour on new duplicated subscriptions. If enabled, the socket passes all subscribe messages to the caller. If disabled, only the first subscription to each filter will be passed. The default is 0 (disabled).

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XPUB

ZMQ_XPUB_VERBOSER: pass duplicate subscribe and unsubscribe messages on XPUB socket

Sets the 'XPUB' socket behaviour on new duplicated subscriptions and unsubscriptions. If enabled, the socket passes all subscribe and unsubscribe messages to the caller. If disabled, only the first subscription to each filter and the last unsubscription from each filter will be passed. The default is 0 (disabled).

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XPUB

ZMQ_XPUB_MANUAL: change the subscription handling to manual

Sets the 'XPUB' socket subscription handling mode manual/automatic. A value of '0' is the default and subscription requests will be handled automatically. A value of '1' will change the subscription requests handling to manual, with manual mode subscription requests are not added to the subscription list. To add subscription the user need to call setsockopt with ZMQ_SUBSCRIBE on XPUB socket.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XPUB

ZMQ_XPUB_MANUAL_LAST_VALUE: change the subscription handling to manual

This option is similar to ZMQ_XPUB_MANUAL. The difference is that ZMQ_XPUB_MANUAL_LAST_VALUE changes the 'XPUB' socket behaviour to send the first message to the last subscriber after the socket receives a subscription and call setsockopt with ZMQ_SUBSCRIBE on 'XPUB' socket. This prevents duplicated messages when using last value caching(LVC).

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XPUB

ZMQ_XPUB_NODROP: do not silently drop messages if SENDHWM is reached

Sets the 'XPUB' socket behaviour to return error EAGAIN if SENDHWM is reached and the message could not be send.

A value of 0 is the default and drops the message silently when the peers SNDHWM is reached. A value of 1 returns an 'EAGAIN' error code if the SNDHWM is reached and ZMQ_DONTWAIT was used.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XPUB, ZMQ_PUB

ZMQ_XPUB_WELCOME_MSG: set welcome message that will be received by subscriber when connecting

Sets a welcome message the will be received by subscriber when connecting. Subscriber must subscribe to the Welcome message before connecting. Welcome message will also be sent on reconnecting. For welcome message to work well user must poll on incoming subscription messages on the XPUB socket and handle them.

Use NULL and length of zero to disable welcome message.

Option value type

binary data

Option value unit

N/A

Default value

NULL

Applicable socket types

ZMQ_XPUB

ZMQ_XSUB_VERBOSE_UNSUBSCRIBE: pass duplicate unsubscribe messages on XSUB socket

Sets the 'XSUB' socket behaviour on duplicated unsubscriptions. If enabled, the socket passes all unsubscribe messages to the caller. If disabled, only the last unsubscription from each filter will be passed. The default is 0 (disabled).

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

ZMQ_XSUB

ZMQ_ONLY_FIRST_SUBSCRIBE: Process only first subscribe/unsubscribe in a multipart message

If set, only the first part of the multipart message is processed as a subscribe/unsubscribe message. The rest are forwarded as user data regardless of message contents.

It not set (default), subscribe/unsubscribe messages in a multipart message are processed as such regardless of their number and order.

Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

ZMQ_XSUB, ZMQ_XPUB

ZMQ_ZAP_DOMAIN: Set RFC 27 authentication domain

Sets the domain for ZAP (ZMQ RFC 27) authentication. A ZAP domain must be specified to enable authentication. When the ZAP domain is empty, which is the default, ZAP authentication is disabled. This is not compatible with previous versions of libzmq, so it can be controlled by ZMQ_ZAP_ENFORCE_DOMAIN which for now is disabled by default. See http://rfc.zeromq.org/spec:27 for more details.

Option value type

character string

Option value unit

N/A

Default value

empty

Applicable socket types

all, when using TCP transport

ZMQ_ZAP_ENFORCE_DOMAIN: Set ZAP domain handling to strictly adhere the RFC

The ZAP (ZMQ RFC 27) authentication protocol specifies that a domain must always be set. Older versions of libzmq did not follow the spec and allowed an empty domain to be set. This option can be used to enabled or disable the stricter, backward incompatible behaviour. For now it is disabled by default, but in a future version it will be enabled by default.

Option value type

int

Option value unit

0, 1

Default value

0

Applicable socket types

all, when using ZAP

ZMQ_TCP_ACCEPT_FILTER: Assign filters to allow new TCP connections

Assign an arbitrary number of filters that will be applied for each new TCP transport connection on a listening socket. If no filters are applied, then the TCP transport allows connections from any IP address. If at least one filter is applied then new connection source ip should be matched. To clear all filters call zmq_setsockopt(socket, ZMQ_TCP_ACCEPT_FILTER, NULL, 0). Filter is a null-terminated string with ipv6 or ipv4 CIDR.

Note
This option is deprecated, please use authentication via the ZAP API and IP address allowing / blocking.
Option value type

binary data

Option value unit

N/A

Default value

no filters (allow from all)

Applicable socket types

all listening sockets, when using TCP transports.

ZMQ_IPC_FILTER_GID: Assign group ID filters to allow new IPC connections

Assign an arbitrary number of filters that will be applied for each new IPC transport connection on a listening socket. If no IPC filters are applied, then the IPC transport allows connections from any process. If at least one UID, GID, or PID filter is applied then new connection credentials should be matched. To clear all GID filters call zmq_setsockopt(socket, ZMQ_IPC_FILTER_GID, NULL, 0).

Note
GID filters are only available on platforms supporting SO_PEERCRED or LOCAL_PEERCRED socket options (currently only Linux and later versions of OS X).
Note
This option is deprecated, please use authentication via the ZAP API and IPC allowing / blocking.
Option value type

gid_t

Option value unit

N/A

Default value

no filters (allow from all)

Applicable socket types

all listening sockets, when using IPC transports.

ZMQ_IPC_FILTER_PID: Assign process ID filters to allow new IPC connections

Assign an arbitrary number of filters that will be applied for each new IPC transport connection on a listening socket. If no IPC filters are applied, then the IPC transport allows connections from any process. If at least one UID, GID, or PID filter is applied then new connection credentials should be matched. To clear all PID filters call zmq_setsockopt(socket, ZMQ_IPC_FILTER_PID, NULL, 0).

Note
PID filters are only available on platforms supporting the SO_PEERCRED socket option (currently only Linux).
Note
This option is deprecated, please use authentication via the ZAP API and IPC allowing / blocking.
Option value type

pid_t

Option value unit

N/A

Default value

no filters (allow from all)

Applicable socket types

all listening sockets, when using IPC transports.

ZMQ_IPC_FILTER_UID: Assign user ID filters to allow new IPC connections

Assign an arbitrary number of filters that will be applied for each new IPC transport connection on a listening socket. If no IPC filters are applied, then the IPC transport allows connections from any process. If at least one UID, GID, or PID filter is applied then new connection credentials should be matched. To clear all UID filters call zmq_setsockopt(socket, ZMQ_IPC_FILTER_UID, NULL, 0).

Note
UID filters are only available on platforms supporting SO_PEERCRED or LOCAL_PEERCRED socket options (currently only Linux and later versions of OS X).
Note
This option is deprecated, please use authentication via the ZAP API and IPC allowing / blocking.
Option value type

uid_t

Option value unit

N/A

Default value

no filters (allow from all)

Applicable socket types

all listening sockets, when using IPC transports.

ZMQ_IPV4ONLY: Use IPv4-only on socket

Set the IPv4-only option for the socket. This option is deprecated. Please use the ZMQ_IPV6 option.

Option value type

int

Option value unit

boolean

Default value

1 (true)

Applicable socket types

all, when using TCP transports.

ZMQ_VMCI_BUFFER_SIZE: Set buffer size of the VMCI socket

The ZMQ_VMCI_BUFFER_SIZE option shall set the size of the underlying buffer for the socket. Used during negotiation before the connection is established.

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: Set min buffer size of the VMCI socket

The ZMQ_VMCI_BUFFER_MIN_SIZE option shall set the min size of the underlying buffer for the socket. Used during negotiation before the connection is established.

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: Set max buffer size of the VMCI socket

The ZMQ_VMCI_BUFFER_MAX_SIZE option shall set the max size of the underlying buffer for the socket. Used during negotiation before the connection is established.

Option value type

uint64_t

Option value unit

bytes

Default value

262144

Applicable socket types

all, when using VMCI transport

ZMQ_VMCI_CONNECT_TIMEOUT: Set connection timeout of the VMCI socket

The ZMQ_VMCI_CONNECT_TIMEOUT option shall set connection timeout for the socket.

Option value type

int

Option value unit

milliseconds

Default value

-1

Applicable socket types

all, when using VMCI transport

ZMQ_MULTICAST_LOOP: Control multicast local loopback

For multicast UDP sender sockets this option sets whether the data sent should be looped back on local listening sockets.

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: Send connect and disconnect notifications

Enable connect and disconnect notifications on a ROUTER socket. When enabled, the socket delivers a zero-length message (with routing-id as first frame) when a peer connects or disconnects. It’s possible to notify both events for a peer by OR-ing the flag values. This option only applies to stream oriented (tcp, ipc) transports.

Note
in DRAFT state, not yet available in stable releases.
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

ZMQ_IN_BATCH_SIZE: Maximal receive batch size

Sets the maximal amount of messages that can be received in a single 'recv' system call. WARNING: this option should almost never be changed. The default has been chosen to offer the best compromise between latency and throughtput. In the vast majority of cases, changing this option will result in worst result if not outright breakages.

Cannot be zero.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

messages

Default value

8192

Applicable socket types

All, when using TCP, IPC, PGM or NORM transport.

ZMQ_OUT_BATCH_SIZE: Maximal send batch size

Sets the maximal amount of messages that can be sent in a single 'send' system call. WARNING: this option should almost never be changed. The default has been chosen to offer the best compromise between latency and throughtput. In the vast majority of cases, changing this option will result in worst result if not outright breakages.

Cannot be zero.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

messages

Default value

8192

Applicable socket types

All, when using TCP, IPC, PGM or NORM transport.

ZMQ_NORM_MODE: NORM Sender Mode

Sets the NORM sender mode to control the operation of the NORM transport. NORM supports fixed rate operation (0='ZMQ_NORM_FIXED'), congestion control mode (1='ZMQ_NORM_CC'), loss-tolerant congestion control (2='ZMQ_NORM_CCL'), explicit congestion notification (ECN)-enabled congestion control (3='ZMQ_NORM_CCE'), and ECN-only congestion control (4='ZMQ_NORM_CCE_ECNONLY'). The default value is TCP-friendly congestion control mode. Fixed rate mode (using datarate set by 'ZMQ_RATE') offers better performance, but care must be taken to prevent data loss. ECN modes will set one of the ECN Capable Transport bits in the given 'ZMQ_TOS' if it is not set already.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

0, 1, 2, 3, 4

Default value

1 ('ZMQ_NORM_CC')

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_UNICAST_NACK: Set NORM Unicast NACK mode

If set, NORM receiver will send Negative ACKnowledgements (NACKs) back to the sender using unicast instead of multicast. NORM transport endpoints specifying a unicast address will enable this by default, but it is disabled by default for multicast addresses.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_BUFFER_SIZE: Set NORM buffer size

Sets NORM buffer size for NORM transport sender, receiver, and stream.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

kilobytes

Default value

2048

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_SEGMENT_SIZE: Set NORM segment size

Sets NORM sender segment size, which is the maximum message payload size of individual NORM messages (ZMQ messages may be split over multiple NORM messages). Ideally, this value should fit within the system/network maximum transmission unit (MTU) after accounting for additional NORM message headers (up to 48 bytes).

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

bytes

Default value

1400

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_BLOCK_SIZE: Set NORM block size

Sets NORM sender block size, which is the number of segments in a NORM FEC coding block. NORM repair operations take place at block boundaries. Maximum value is 255, but parity packets ('ZMQ_NORM_NUM_PARITY') are limited to a value of (255 - 'ZMQ_NORM_BLOCK_SIZE'). Minimum value is ('ZMQ_NORM_NUM_PARITY' + 1). Effective value may be different based on the settings of 'ZMQ_NORM_NUM_PARITY' and 'ZMQ_NORM_NUM_AUTOPARITY' if invalid settings are provided.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

>0, ⇐255

Default value

16

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_NUM_PARITY: Set number of NORM parity segments

Sets the maximum number of NORM parity symbol segments that the sender is willing to calculate per FEC coding block for the purpose of reparing lost data. Maximum value is 255, but is further limited to a value of (255 - 'ZMQ_NORM_BLOCK_SIZE'). Minimum value is 'ZMQ_NORM_NUM_AUTOPARITY'. Effective value may be different based on the setting of 'ZMQ_NORM_NUM_AUTOPARITY' if invalid settings are provided.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

>0, <255

Default value

4

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_NUM_AUTOPARITY: Set number of proactive NORM parity segments

Sets the number of NORM parity symbol segments that the sender will proactively send at the end of each FEC coding block. By default, no proactive parity segments will be sent; instead, parity segments will only be sent in response to repair requests (NACKs). Maximum value is 255, but is further limited to a maximum value of 'ZMQ_NORM_NUM_PARITY'.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

>=0, <255

Default value

0

Applicable socket types

All, when using NORM transport.

ZMQ_NORM_PUSH: Enable NORM push mode

Enables NORM stream push mode, which alters the behavior of the sender when enqueueing new data. By default, NORM will stop accepting new messages while waiting for old data to be transmitted and/or repaired. Enabling push mode discards the oldest data (which may be pending repair or may never have been transmitted) in favor of accepting new data. This may be useful in cases where it is more important to quickly deliver new data instead of reliably delivering older data.

Note
in DRAFT state, not yet available in stable releases.
Option value type

int

Option value unit

boolean

Default value

0 (false)

Applicable socket types

All, when using NORM transport.

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 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

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);

SEE ALSO

AUTHORS

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