ip

function open()
  local bOpen, sFreeSide = false, nil
  for n,sSide in pairs(rs.getSides()) do
    if peripheral.getType( sSide ) == "modem" then
      sFreeSide = sSide
      if rednet.isOpen( sSide ) then
        bOpen = true
        break
      end
    end
  end
  if not bOpen then
    if sFreeSide then
      print( "No modem active. Opening "..sFreeSide.." modem" )
      rednet.open( sFreeSide )
      return true
    else
      print( "No modem attached" )
      return false
    end
  end
  return true
end

local localIP
local MainGate

function getIP(route)
  MainGate=nil
  localIP=nil
  route=route or '*'
  rednet.broadcast('T=1|D='..route..'|S=*|getip')
  local mess,sIP,dIP,gate
  repeat
    mess,sIP,dIP,gate=receive(2)
--    print(mess,' ',sIP)
    if mess=='setip' then
      MainGate=gate
      localIP=dIP
      break
    end
  until not mess
  if localIP then print("IP is ",localIP)
  else print("Can't receive IP.") end
  return localIP
end

function send(dIP,mess,T)
  if MainGate then
    rednet.send(MainGate,'T='..(T or 99)..'|D='..dIP..'|S='..localIP..'|'..mess)
  end
end

function receive(timeout)
  local gate,mess
  local sIP,dIP
  while true do
    gate,mess=rednet.receive(timeout)
--    print(gate,' ',mess)
    if not gate then return end  --timeout
    if not MainGate or MainGate==gate then
      dIP,sIP,mess=mess:match('T=.-|D=(.-)|S=(.-)|(.*)')
      if mess=='ping' then
        send(sIP,'pong')
      else
        return mess,sIP,dIP,gate
      end
    end
  end
end

function sendrec(dIP,mess,timeout)
  send(dIP,mess)
  return receive(timeout or 3)
end