ZMQ\_MSG\_ROUTING\_ID(3) 0MQ Manual ZMQ\_MSG\_ROUTING\_ID(3)

# [NAME](#NAME)

zmq\_msg\_routing\_id - return routing ID for message, if any

# [SYNOPSIS](#SYNOPSIS)

**uint32\_t zmq\_msg\_routing\_id (zmq\_msg\_t \*message);**

# [DESCRIPTION](#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](#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](#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](#SEE_ALSO)

[**zmq\_msg\_set\_routing\_id**(3)](/man/os/zeromq/zmq_msg_set_routing_id.3)

# [AUTHORS](#AUTHORS)

This page was written by the 0MQ community. To make a change please read the 0MQ Contribution Policy at **http://www.zeromq.org/docs:contributing**.

08/29/2026 0MQ 4.3.5

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Document: zmq_msg_routing_id(3) from zeromq 4.3.5-r13 (Chainguard OS)
Source: https://github.com/zeromq/libzmq