= zmq_msg_routing_id(3)


== NAME
zmq_msg_routing_id - return routing ID for message, if any


== SYNOPSIS
*uint32_t zmq_msg_routing_id (zmq_msg_t '*message');*


== DESCRIPTION
The _zmq_msg_routing_id()_ function returns the routing ID for the message,
if any. The routing ID is set on all messages received from a 'ZMQ_SERVER'
socket. To send a message to a 'ZMQ_SERVER' socket you must set the routing
ID of a connected 'ZMQ_CLIENT' peer. Routing IDs are transient.


== RETURN VALUE
The _zmq_msg_routing_id()_ function shall return zero if there is no routing
ID, otherwise it shall return an unsigned 32-bit integer greater than zero.


== EXAMPLE
.Receiving a client message and routing ID
----
void *ctx = zmq_ctx_new ();
assert (ctx);

void *server = zmq_socket (ctx, ZMQ_SERVER);
assert (server);
int rc = zmq_bind (server, "tcp://127.0.0.1:8080");
assert (rc == 0);

zmq_msg_t message;
rc = zmq_msg_init (&message);
assert (rc == 0);

//  Receive a message from socket
rc = zmq_msg_recv (server, &message, 0);
assert (rc != -1);
uint32_t routing_id = zmq_msg_routing_id (&message);
assert (routing_id);
----


== SEE ALSO
* xref:zmq_msg_set_routing_id.adoc[zmq_msg_set_routing_id]


== 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/>.
