NAME¶

zmq_socket - create 0MQ socket

SYNOPSIS¶

void *zmq_socket (void *context, int type );

DESCRIPTION¶

The zmq_socket() function shall create a 0MQ socket within the specified context and return an opaque handle to the newly created socket. The type argument specifies the socket type, which determines the semantics of communication over the socket. The newly created socket is initially unbound, and not associated with any endpoints. In order to establish a message flow a socket must first be connected to at least one endpoint with zmq_connect(3), or at least one endpoint must be created for accepting incoming connections with zmq_bind(3). Key differences to conventional sockets. Generally speaking, conventional sockets present a synchronous interface to either connection-oriented reliable byte streams (SOCK_STREAM), or connection-less unreliable datagrams (SOCK_DGRAM). In comparison, 0MQ sockets present an abstraction of an asynchronous message queue, with the exact queueing semantics depending on the socket type in use. Where conventional sockets transfer streams of bytes or discrete datagrams, 0MQ sockets transfer discrete messages. 0MQ sockets being asynchronous means that the timings of the physical connection setup and tear down, reconnect and effective delivery are transparent to the user and organized by 0MQ itself. Further, messages may be queued in the event that a peer is unavailable to receive them. Conventional sockets allow only strict one-to-one (two peers), many-to-one (many clients, one server), or in some cases one-to-many (multicast) relationships. With the exception of ZMQ_PAIR, 0MQ sockets may be connected to multiple endpoints using zmq_connect(), while simultaneously accepting incoming connections from multiple endpoints bound to the socket using zmq_bind(), thus allowing many-to-many relationships. Thread safety. 0MQ sockets are not thread safe. Applications MUST NOT use a socket from multiple threads except after migrating a socket from one thread to another with a "full fence" memory barrier. Socket types. The following sections present the socket types defined by 0MQ, grouped by the general messaging pattern which is built from related socket types.

Request-reply pattern¶

The request-reply pattern is used for sending requests from a client to one or more instances of a service, and receiving subsequent replies to each request sent. ZMQ_REQ ZMQ_REP ZMQ_DEALER ZMQ_ROUTER

Publish-subscribe pattern¶

The publish-subscribe pattern is used for one-to-many distribution of data from a single publisher to multiple subscribers in a fan out fashion. ZMQ_PUB ZMQ_SUB

Pipeline pattern¶

The pipeline pattern is used for distributing data to nodes arranged in a pipeline. Data always flows down the pipeline, and each stage of the pipeline is connected to at least one node. When a pipeline stage is connected to multiple nodes data is round-robined among all connected nodes. ZMQ_PUSH ZMQ_PULL

Exclusive pair pattern¶

The exclusive pair pattern is used to connect a peer to precisely one other peer. This pattern is used for inter-thread communication across the inproc transport. ZMQ_PAIR

RETURN VALUE¶

The zmq_socket() function shall return an opaque handle to the newly created socket if successful. Otherwise, it shall return NULL and set errno to one of the values defined below.

ERRORS¶

EINVAL EFAULT EMFILE ETERM

SEE ALSO¶

zmq_init(3) zmq_setsockopt(3) zmq_bind(3) zmq_connect(3) zmq_send(3) zmq_recv(3) zmq_inproc(7) zmq(7)

AUTHORS¶

This manual page was written by the 0MQ community.