# zmq_udp(7) Manual Page

## 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 ØMQ 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

zmq_connect(3) zmq_setsockopt(3) zmq_tcp(7) zmq_ipc(7) zmq_inproc(7) zmq_vmci(7) 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.