ØMQ Manual - ØMQ/4.2.0
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.
ØMQ provides the the following transports:
- unicast transport using TCP, see zmq_tcp(7)
- local inter-process communication transport, see zmq_ipc(7)
- local in-process (inter-thread) communication transport, see zmq_inproc(7)
- pgm, epgm
- reliable multicast transport using PGM, see zmq_pgm(7)
- 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.
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 ØMQ 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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