= zmq_connect_peer(3)


== NAME
zmq_connect_peer - create outgoing connection from socket and return the connection routing id in thread-safe and atomic way.


== SYNOPSIS
*uint32_t zmq_connect_peer (void '*socket', const char '*endpoint');*


== DESCRIPTION
The _zmq_connect_peer()_ function connects a 'ZMQ_PEER' socket to an 'endpoint' and then returns the endpoint 'routing_id'.

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.

The function is supported only on the 'ZMQ_PEER' socket type and would return `0` with 'errno' set to 'ENOTSUP' otherwise.

The _zmq_connect_peer()_ support the following transports:

'tcp':: unicast transport using TCP, see xref:zmq_tcp.adoc[zmq_tcp]
'ipc':: local inter-process communication transport, see xref:zmq_ipc.adoc[zmq_ipc]
'inproc':: local in-process (inter-thread) communication transport, see xref:zmq_inproc.adoc[zmq_inproc]
'ws':: unicast transport using WebSockets, see xref:zmq_ws.adoc[zmq_ws]
'wss':: unicast transport using WebSockets over TLS, see xref:zmq_wss.adoc[zmq_wss]

== RETURN VALUE
The _zmq_connect_peer()_ function returns the peer 'routing_id' if successful. Otherwise it returns
`0` 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 with 'ZMQ_PEER'.
*ENOCOMPATPROTO*::
The requested 'transport' protocol is not compatible with the socket type.
*ETERM*::
The 0MQ '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.
*ENOTSUP*::
The socket is not of type 'ZMQ_PEER'.
*EFAULT*::
The 'ZMQ_IMMEDIATE' option is set on the socket.

== EXAMPLE
.Connecting a peer socket to a TCP transport and sending a message
----
/* Create a ZMQ_SUB socket */
void *socket = zmq_socket (context, ZMQ_PEER);
assert (socket);
/* Connect it to the host server001, port 5555 using a TCP transport */
uint32_t routing_id = zmq_connect (socket, "tcp://server001:5555");
assert (routing_id == 0);
/* Sending a message to the peer  */
zmq_msg_t msg;
int rc = zmq_msg_init_data (&msg, "HELLO", 5, NULL, NULL);
assert (rc == 0);
rc = zmq_msg_set_routing_id (&msg, routing_id);
assert (rc == 0);
rc = zmq_msg_send (&msg, socket, 0);
assert (rc == 5);
rc = zmq_msg_close (&msg);
assert (rc == 0);
----


== SEE ALSO
* xref:zmq_connect.adoc[zmq_connect]
* xref:zmq_bind.adoc[zmq_bind]
* xref:zmq_socket.adoc[zmq_socket]
* xref:zmq.adoc[zmq]


== AUTHORS
This page was written by the 0MQ community. To make a change please
read the 0MQ Contribution Policy at <https://zeromq.org/how-to-contribute/>.
