Listener

if not fs.exists("msglist") then
  nFile = fs.open("msglist", "w")
  nFile.writeLine("messages = {}")
  nFile.close()
end

function reverseTable(table)
  num = 1
  local result = {}
  for i = #table, 1, -1 do
    result[num] = {}
    result[num][1] = table[i][1]
    result[num][2] = table[i][2]
    num = num + 1
  end
  return result
end

function serialize(table)
  local result = "messages = {}\n"
  local revTab = reverseTable(table)
  for i, v in pairs(revTab) do
    result = result .. "messages[" .. tostring(i) .. "] = {}\n"
    for k, e in pairs(v) do
      result = result .. "messages[" .. tostring(i) .. "][" .. tostring(k) .. "] = \"" .. tostring(e) .. "\"\n"
    end
  end
  return result
end

while true do
  os.loadAPI("msglist")
  id, message, protocol = nil, nil, nil
  id, message, protocol = rednet.receive()
  print(id, message, "prot", protocol)
  if protocol == "getmsglist" then
    print("getmsglist")
    rednet.send(id, serialize(msglist.messages), "sendmsglist")
  else
    print(message)
    rFile = fs.open("msglist", "r")
    local previous = rFile.readAll()
    rFile.close()
    wFile = fs.open("msglist", "w")
    wFile.write(previous .. "\n")
    wFile.writeLine("messages[" .. #msglist.messages + 1 .. "] = {}")
    wFile.writeLine("messages[" .. #msglist.messages + 1 .. "][1] = \"" .. tostring(id) .. ": " .. tostring(message) .. "\"")
    wFile.writeLine("messages[" .. #msglist.messages + 1 .. "][2] = \"" .. tostring(os.day()) .. ":" .. tostring(os.time()) .. "\"")
    wFile.close()
  end
end