handshake.lua

local component = require("component")
local event = require("event")
local modem = component.modem
modem.open(1024)
listeners={}

event.listen("modem_message", function(_,_,blah,_,_,_)
 dup = 0
 for i = 1, #listeners do
  if blah == listeners[i] then
   dup = 1
  end
 end
 if dup ~= 1 then
  table.insert(listeners, blah)
 end
 print(blah)
end)

function helloisanyonethere(port,msg)
 return modem.broadcast(port,msg)
end  -- ¯\_(ツ)_/¯


while true do
 for i = 1, #listeners do
  print(listeners[i])
 end
 os.sleep(1)
--print(helloisanyonethere(1024,"ping"))
end