= zmq_udp(7)


== NAME
zmq_udp - 0MQ UDP multicast and unicast transport


== SYNOPSIS
UDP is unreliable protocol transport of data over IP networks.
UDP support both unicast and multicast communication.


== DESCRIPTION
UDP transport can only be used with the 'ZMQ_RADIO' and
'ZMQ_DISH' socket types.

== ADDRESSING
A 0MQ 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.

For the UDP transport, the transport is `udp`.
The meaning of the 'address' part is defined below.

Binding a socket
----------------
With 'udp' we can only bind the 'ZMQ_DISH' socket type.
When binding a socket using _zmq_bind()_ with the 'udp'
transport the 'endpoint' shall be interpreted as an 'interface' followed by a
colon and the UDP port number to use.

An 'interface' may be specified by either of the following:

* The wild-card `*`, meaning all available interfaces.
* The name of the network interface (i.e. eth0, lo, wlan0 etc...)
* The primary address assigned to the interface, in its numeric representation.
* Multicast address in its numeric representation the socket should join.

The UDP port number may be specified a numeric value, usually above
1024 on POSIX systems.

Connecting a socket
-------------------
With 'udp' we can only connect the 'ZMQ_RADIO' socket type.
When connecting a socket to a peer address using _zmq_connect()_ with the 'udp'
transport, the 'endpoint' shall be interpreted as a 'peer address' followed by
a colon and the UDP port number to use.

A 'peer address' may be specified by either of the following:

* The IPv4 or IPv6 address of the peer, in its numeric representation
  or using its hostname.
* Multicast address in its numeric representation.

== EXAMPLES
.Binding a socket
----
//  Unicast - UDP port 5555 on all available interfaces
rc = zmq_bind(dish, "udp://*:5555");
assert (rc == 0);
//  Unicast - UDP port 5555 on the local loop-back interface
rc = zmq_bind(dish, "udp://127.0.0.1:5555");
assert (rc == 0);
//  Unicast - UDP port 5555 on interface eth1
rc = zmq_bind(dish, "udp://eth1:5555");
assert (rc == 0);
//  Multicast - UDP port 5555 on a Multicast address
rc = zmq_bind(dish, "udp://239.0.0.1:5555");
assert (rc == 0);
//  Same as above but joining only on interface eth0
rc = zmq_bind(dish, "udp://eth0;239.0.0.1:5555");
assert (rc == 0);
//  Same as above using IPv6 multicast
rc = zmq_bind(dish, "udp://eth0;[ff02::1]:5555");
assert (rc == 0);
----


.Connecting a socket
----
//  Connecting using an Unicast IP address
rc = zmq_connect(radio, "udp://192.168.1.1:5555");
assert (rc == 0);
//  Connecting using a Multicast address
rc = zmq_connect(socket, "udp://239.0.0.1:5555);
assert (rc == 0);
//  Connecting using a Multicast address using local interface wlan0
rc = zmq_connect(socket, "udp://wlan0;239.0.0.1:5555);
assert (rc == 0);
//  Connecting to IPv6 multicast
rc = zmq_connect(socket, "udp://[ff02::1]:5555);
assert (rc == 0);
----


== SEE ALSO
* xref:zmq_connect.adoc[zmq_connect]
* xref:zmq_setsockopt.adoc[zmq_setsockopt]
* xref:zmq_tcp.adoc[zmq_tcp]
* xref:zmq_ipc.adoc[zmq_ipc]
* xref:zmq_inproc.adoc[zmq_inproc]
* xref:zmq_vmci.adoc[zmq_vmci]
* 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/>.
