zmq_connect - create outgoing connection from socket


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


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.

0MQ provides the the following transports:


unicast transport using TCP, see zmq_tcp


local inter-process communication transport, see zmq_ipc


local in-process (inter-thread) communication transport, see zmq_inproc

'pgm', 'epgm'

reliable multicast transport using PGM, see zmq_pgm


virtual machine communications interface (VMCI), see zmq_vmci


unreliable unicast and multicast using UDP, see zmq_udp

Every 0MQ socket type except 'ZMQ_PAIR' and 'ZMQ_CHANNEL' supports one-to-many and many-to-one semantics. The precise semantics depend on the socket type and are defined in zmq_socket

for most transports and socket types the connection is not performed immediately but as needed by 0MQ. 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 ZMQ_PAIR and ZMQ_CHANNEL sockets are an exception, as they 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 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.
for some socket types, multiple connections to the same endpoint don’t really make sense (see For those socket types, any attempt to connect to an already connected endpoint is silently ignored (i.e., returns zero). This behavior applies to ZMQ_DEALER, ZMQ_SUB, ZMQ_PUB, and ZMQ_REQ socket types.


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



The endpoint supplied is invalid.


The requested 'transport' protocol is not supported.


The requested 'transport' protocol is not compatible with the socket type.


The 0MQ 'context' associated with the specified 'socket' was terminated.


The provided 'socket' was invalid.


No I/O thread is available to accomplish the task.


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);



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