CRFv3.1 File Transfer Server

-- File Transfer Server over CRFv3.1

-- Packet structure:
-- [1] : Ident string
-- [2] : Action
-- [3] : Target
-- [4] : Parameter 1
-- [5] : Parameter 2

local args = {...}

local filePath = "server/"

-- Standard error messages:
local e_noexist = textutils.serialize({"FileTransfer", "Error", "File does not exist"})
local e_exist = textutils.serialize({"FileTransfer", "Error", "File already exists"})
local e_isdir = textutils.serialize({"FileTransfer", "Error", "File is a directory"})
local e_hasdata = textutils.serialize({"FileTransfer", "Error", "Directory contains files"})
-- Not an error message:
local m_okay = textutils.serialize({"FileTransfer", "Okay"})

if not LANClient then
    error("LAN Client API not loaded.")
end

while true do
    local sender, data = LANClient.receive()
    data = textutils.unserialize(data)
    if type(data) == "table" then
        if data[1] == "FileTransfer" then
            if data[2] == "read" then
                if not fs.exists(data[3]) then
                    LANClient.send(sender, e_noexist)
                else
                    if data[4] then -- Binary flag
                        local f = fs.open(data[3], "rb")
                        local bytes = {}
                        local lastPause = os.clock()
                        while true do
                            local byte = f.read()
                            if not byte then
                                break
                            else
                                table.insert(bytes, byte)
                            end
                            if (os.clock() - lastPause) >= 2.90 then
                                os.queueEvent("")
                                os.pullEvent("")
                                lastPause = os.clock()
                            end
                        end
                        f.close()
                        LANClient.send(sender, textutils.serialize({"FileTransfer", "data", bytes}))
                    else
                        local f = fs.open(data[3], "r")
                        local text = f.readAll()
                        f.close()
                        LANClient.send(sender, textutils.serialize({"FileTransfer", "data", text}))
                    end
                end
            elseif data[2] == "write" then
                if data[5] then
                    local f = fs.open(data[3], "wb")
                    local lastPause = os.clock()
                    for i=1, #data[4] do
                        f.write(data[4][i])
                        if (os.clock() - lastPause) >= 2.90 then
                            os.queueEvent("")
                            os.pullEvent("")
                            lastPause = os.clock()
                        end
                    end
                    f.close()
                    LANClient.send(sender, m_okay)
                else
                    local f = fs.open(data[3], "w")
                    f.write(data[4])
                    f.close()
                    LANClient.send(sender, m_okay)
                end
            elseif data[2] == "mkdir" then
                if fs.exists(data[3]) then
                    LANClient.send(sender, e_exist)
                else
                    fs.makeDir(data[3])
                    LANClient.send(sender, m_okay)
                end
            elseif data[2] == "delete" then
                if not fs.exists(data[3]) then
                    LANClient.send(sender, e_noexist)
                else
                    fs.delete(data[3])
                    LANClient.send(sender, m_okay)
                end
            elseif data[2] == "list" then
                if not fs.exists(data[3]) then
                    LANClient.send(sender, e_noexist)
                else
                    LANClient.send(sender, textutils.serialize({"FileTransfer", "list", fs.list(data[3])}))
                end
            end
        end
    end
end