ØMQ Manual - ØMQ/2.0.11


zmq_connect - connect a socket


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


The zmq_connect() function shall connect the socket referenced by the socket argument to the endpoint specified by the endpoint argument.

The endpoint argument is a string consisting of two parts as follows: transport ://address. The transport part specifies the underlying transport protocol to use. The meaning of the address part is specific to the underlying transport protocol selected.

The following transports are defined:

local in-process (inter-thread) communication transport, see zmq_inproc(7)
local inter-process communication transport, see zmq_ipc(7)
unicast transport using TCP, see zmq_tcp(7)
pgm, epgm
reliable multicast transport using PGM, see zmq_pgm(7)

With the exception of ZMQ_PAIR sockets, a single socket may be connected to multiple endpoints using zmq_connect(), while simultaneously accepting incoming connections from multiple endpoints bound to the socket using zmq_bind(). Refer to zmq_socket(3) for a description of the exact semantics involved when connecting or binding a socket to multiple endpoints.

The connection will not be performed immediately but as needed by ØMQ. Thus a successful invocation of zmq_connect() does not indicate that a physical connection was or can actually be established.

Return value

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


The requested transport protocol is not supported.
The requested transport protocol is not compatible with the socket type.
The ØMQ context associated with the specified socket was terminated.
The provided socket was not valid (NULL).


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);

See also

zmq_bind(3) zmq_socket(3) zmq(7)


This ØMQ manual page was written by Martin Sustrik <moc.mpb052|kirtsus#moc.mpb052|kirtsus> and Martin Lucina <ks.anletok|otam#ks.anletok|otam>.