ZMQ_MSG_GETS(3) 0MQ Manual ZMQ_MSG_GETS(3)
NAME
zmq_msg_gets - get message metadata property
SYNOPSIS
const char *zmq_msg_gets (zmq_msg_t *message, const char *property);
DESCRIPTION
The zmq_msg_gets() function shall return the string value for the
metadata property specified by the property argument for the message
pointed to by the message argument. Both the property argument and the
value shall be NULL-terminated UTF8-encoded strings.
Metadata is defined on a per-connection basis during the ZeroMQ
connection handshake as specified in <rfc.zeromq.org/spec:37>.
Applications can set metadata properties using zmq_setsockopt(3) option
ZMQ_METADATA. Application metadata properties must be prefixed with X-.
In addition to application metadata, the following ZMTP properties can
be retrieved with the zmq_msg_gets() function:
Socket-Type
Routing-Id
Note: Identity is a deprecated alias for Routing-Id.
Additionally, when available for the underlying transport, the
Peer-Address property will return the IP address of the remote endpoint
as returned by getnameinfo(2).
The names of these properties are also defined in zmq.h as
ZMQ_MSG_PROPERTY_SOCKET_TYPE ZMQ_MSG_PROPERTY_ROUTING_ID, and
ZMQ_MSG_PROPERTY_PEER_ADDRESS. Currently, these definitions are only
available as a DRAFT API.
Other properties may be defined based on the underlying security
mechanism, see ZAP authenticated connection sample below.
RETURN VALUE
The zmq_msg_gets() function shall return the string value for the
property if successful. Otherwise it shall return NULL and set errno to
one of the values defined below. The caller shall not modify or free
the returned value, which shall be owned by the message. The encoding
of the property and value shall be UTF8.
ERRORS
EINVAL
The requested property is unknown.
EXAMPLE
Getting the ZAP authenticated user id for a message:.
zmq_msg_t msg;
zmq_msg_init (&msg);
rc = zmq_msg_recv (&msg, dealer, 0);
assert (rc != -1);
const char *user_id = zmq_msg_gets (&msg, ZMQ_MSG_PROPERTY_USER_ID);
zmq_msg_close (&msg);
SEE ALSO
zmq(7) zmq_setsockopt(3)
AUTHORS
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0MQ 4.3.4 01/18/2023 ZMQ_MSG_GETS(3)
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