# zmq_connect_peer(3) Manual Page

## 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 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)

ws

  unicast transport using WebSockets, see zmq_ws(7)

wss

  unicast transport using WebSockets over TLS, see zmq_wss(7)

## 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 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.

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

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

## AUTHORS

This page was written by the ØMQ community. To make a change please read the ØMQ Contribution Policy at http://www.zeromq.org/docs:contributing.