concurrent = require 'concurrent'

concurrent.setoption('trapexit', true)

function pong()

while true do

local msg = concurrent.receive()

if msg.signal == 'EXIT' then

break

elseif msg.body == 'ping' then

print('pong received ping')

concurrent.send(msg.from, { body = 'pong' })

end

end

print('pong finished')

end

function ping(n, pid)

concurrent.link(pid)

for i = 1, n do

concurrent.send(pid, { from = concurrent.self(), body = 'ping' })

local msg = concurrent.receive()

if msg.body == 'pong' then print('ping received pong') end

end

print('ping finished')

concurrent.exit('finished')

end

pid = concurrent.spawn(pong)

concurrent.spawn(ping, 3, pid)

concurrent.loop()