zmq_setsockopt - Man Page

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(3) for details on allocating the number of I/O threads for a specific context.

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.

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.

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.

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

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).

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.

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.

Sets the socket’s long term public key. You must set this on CURVE client sockets, see zmq_curve(7). 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(3). To derive the public key from a secret key, use zmq_curve_public(3).

Sets the socket’s long term secret key. You must set this on both CURVE client and server sockets, see zmq_curve(7). 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(3). To derive the public key from a secret key, use zmq_curve_public(3).

Defines whether the socket will act as server for CURVE security, see zmq_curve(7). 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.

Sets the socket’s long term server key. You must set this on CURVE client sockets, see zmq_curve(7). 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(3).

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.

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.

Defines whether communications on the socket will be encrypted, see zmq_gssapi(7). A value of 1 means that communications will be plaintext. A value of 0 means communications will be encrypted.

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

Defines whether the socket will act as server for GSSAPI security, see zmq_gssapi(7). A value of 1 means the socket will act as GSSAPI server. A value of 0 means the socket will act as GSSAPI client.

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

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).

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).

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.

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.

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.

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.

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.

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

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.

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.

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.

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(3) or closed with zmq_close(3), and further affects the termination of the socket’s context with zmq_ctx_term(3). 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

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.

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(3)).

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.

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.

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(7). If you set this to a null value, the security mechanism used for connections shall be NULL, see zmq_null(3).

Defines whether the socket will act as server for PLAIN security, see zmq_plain(7). 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.

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(7). If you set this to a null value, the security mechanism used for connections shall be NULL, see zmq_null(3).

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).

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)

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.

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.

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.

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(3) for details on the exact action taken for each socket type.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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(3) for details on the exact action taken for each socket type.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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).

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.

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).

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.

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.

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).

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.

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.

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.

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.

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).

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).

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).

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

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.

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.

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.

The ZMQ_VMCI_CONNECT_TIMEOUT option shall set connection timeout for the socket.

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

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.

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.

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.

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.

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.

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

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).

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.

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.

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.

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.