Rednet Monitor

--[[
  Wolfe's Rednet Monitor
  Command: pastebin run a67ru7BV [protocol]
]]

--- Prints in multiple colors
function print_colored (text_pairs)
  for _, pair in pairs(text_pairs) do
    term.setTextColor(pair[2] or colors.white)
    term.write(pair[1])
  end

  print('')
end

--- Prints data with timestamp
function log (data, header)
  local time = os.date('%H:%M:%S')

  if header then
    -- Renders header when needed
    print_colored({
      { ('[%s] '):format(time), colors.orange },
      { header or '', colors.lime },
    })

    term.setTextColor(colors.white)
    print(data)
  else
    -- Writes on same line
    print_colored({
      { ('[%s] '):format(time), colors.orange },
      { data },
    })
  end
end

-- If any monitors are connected, redirects feed into them
local monitor = peripheral.find('monitor')
if monitor then
  monitor.setTextScale(0.5)
  term.redirect(monitor)
end

-- Clears everything
term.setCursorPos(1, 1)
term.clear()

-- Opens our modem
if peripheral.find('modem') then
  peripheral.find('modem', rednet.open)
  log('Connected to rednet!')
else
  error('No modem connected!')
end

-- Gets our program arguments
local args = {...}
local protocol_filter = args[1] or nil

-- Lets user know which protocol is being listened
if protocol_filter then
  log(('Listening to protocol "%s"...'):format(protocol_filter))
else
  log('Listening to all messages...')
end

print('')

-- Starts listening
while true do
  -- Pulls next message
  local id, message = rednet.receive(protocol_filter)

  -- Suffix (to indicate what channel was sent to)
  local suffix = ''
  if protocol_filter then
    suffix = (' @ %s'):format(protocol_filter)
  end

  -- Prints message
  log(message, ('from #%d%s:'):format(id, suffix))
  print('')
end