require 'socket'
$port = 4321

sThread = Thread.start do       # run server in a thread
    server = UDPSocket.open
    server.bind(nil, $port)
    2.times {
        p server.recvfrom(64)
    }
end

# Ad-hoc client
UDPSocket.open.send("ad hoc", 0, 'localhost', $port)

# Connection vased client
sock = UDPSocket.open
sock.connect('localhost', $port)
sock.send("connection-based", 0)
sThread.join