How to start iperf3 server in UDP mode?

I would like to test UDP connectivity with iperf3 but do not know how to start it in UDP server mode.

iperf3 -s only opens a TCP socket:

root@srv ~# lsof -i -P | grep iperf3
iperf3    21030            root    3u  IPv4 15606995      0t0  TCP *:5201 (LISTEN)

The syntax is a bit different for iperf3. Example 1Mbps udp test:

server side:

iperf3 -s

client side:

iperf3 -u -c client.ip.address -b 1M

What I find really interesting is the server-side doesn't start listening on the udp port until it receives the first incoming udp packet. This is weirdly unintuitive.

You can open UDP socket in the port 5003 using the below command.

iperf3 -s -p 5003