zmq_connect(3)

ØMQ Manual - ØMQ/4.2.2

Name

zmq_connect - create outgoing connection from socket

Synopsis

int zmq_connect (void *socket, const char *endpoint);

Description

The zmq_connect() function connects the socket to an endpoint and then accepts incoming connections on that endpoint.

The endpoint is a string consisting of a transport :// followed by an address. The transport specifies the underlying protocol to use. The address specifies the transport-specific address to connect to.

ØMQ provides the the following transports:

tcp: unicast transport using TCP, see zmq_tcp(7)
ipc: local inter-process communication transport, see zmq_ipc(7)
inproc: local in-process (inter-thread) communication transport, see zmq_inproc(7)
pgm, epgm: reliable multicast transport using PGM, see zmq_pgm(7)
vmci: virtual machine communications interface (VMCI), see zmq_vmci(7)

Every ØMQ socket type except ZMQ_PAIR supports one-to-many and many-to-one semantics. The precise semantics depend on the socket type and are defined in zmq_socket(3).

for most transports and socket types the connection is not performed immediately but as needed by ØMQ. Thus a successful call to zmq_connect() does not mean that the connection was or could actually be established. Because of this, for most transports and socket types the order in which a server socket is bound and a client socket is connected to it does not matter. The first exception is when using the inproc:// transport: you must call zmq_bind() before calling zmq_connect(). The second exception are ZMQ_PAIR sockets, which do not automatically reconnect to endpoints.

following a zmq_connect(), for socket types except for ZMQ_ROUTER, the socket enters its normal ready state. By contrast, following a zmq_bind() alone, the socket enters a mute state in which the socket blocks or drops messages according to the socket type, as defined in zmq_socket(3). A ZMQ_ROUTER socket enters its normal ready state for a specific peer only when handshaking is complete for that peer, which may take an arbitrary time.

Return value

The zmq_connect() function returns zero if successful. Otherwise it returns -1 and sets errno to one of the values defined below.

Errors

EINVAL: The endpoint supplied is invalid.
EPROTONOSUPPORT: The requested transport protocol is not supported.
ENOCOMPATPROTO: The requested transport protocol is not compatible with the socket type.
ETERM: The ØMQ context associated with the specified socket was terminated.
ENOTSOCK: The provided socket was invalid.
EMTHREAD: No I/O thread is available to accomplish the task.

Example

Connecting a subscriber socket to an in-process and a tcp transport

/* Create a ZMQ_SUB socket */
void *socket = zmq_socket (context, ZMQ_SUB);
assert (socket);
/* Connect it to an in-process transport with the address 'my_publisher' */
int rc = zmq_connect (socket, "inproc://my_publisher");
assert (rc == 0);
/* Connect it to the host server001, port 5555 using a TCP transport */
rc = zmq_connect (socket, "tcp://server001:5555"); assert (rc == 0);

Authors

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0MQ Api