coro_example.lua

local socket = require 'socket'

function dispatch ()
    local i = 1
    local timedout = {}
    while true do
        if threads[i] == nil then
            -- больше нет нитей?
            if threads[1] == nil then break end
            i = 1
            -- перезапускает цикл
            timedout = {}
        end
        local status, res = coroutine.resume(threads[i])
        if not res then
            -- нить выполнила свою задачу?
            table.remove(threads, i)
        else
            -- превышено время ожидания
            i = i + 1
            timedout[#timedout + 1] = res
            if #timedout == #threads then
                -- все нити заблокированы?
                socket.select(timedout)
            end
        end
    end
end

function download (host, fileName)
    local c = assert(socket.connect(host, 80))
    local count = 0 -- counts number of bytes read
    c:send("GET " .. fileName .. " HTTP/1.0\r\n\r\n")
    print("fileName", getName(fileName))
    local newFile = io.open(getName(fileName), "w")
    
    while true do
        local s, status = receive(c)
        newFile:write(s)
        count = count + #s
        if status == "closed" then break end
    end

    f:close()
    c:close()
    print(fileName, count)
end

function receive (connection)
    connection:settimeout(0)
    -- не блокирует данные
    local s, status, partial = connection:receive(2^10)
    if status == "timeout" then
        coroutine.yield(connection)
    end
    return s or partial, status
end

threads = {}
-- список всех живых нитей
function get (host, file)
    -- создает сопрограмму
    local co = coroutine.create(function ()
        download(host, file)
    end)
    -- вставляет ее в список
    table.insert(threads, co)
end

function getName(fname)
    local _, second = string.match(fname, "(.+)/(.+)")
    return second
end

function matchTest()
    print(getName("/TR/html401/html40.txt"))
    print(getName("/TR/2002/REC-xhtml1-20020801/xhtml1.pdf"))
    print(getName("/TR/REC-html32.html"))
    print(getName("/TR/2000/REC-DOM-Level-2-Core-20001113/DOM2-Core.txt"))
end

for k, v in pairs(arg) do
    if v == "--match-test" then matchTest() os.exit(0) 
    elseif v == "--help" then 
        print("Use --match-test parameter to run string.match tests")
        print("Use --help to see this text")
        os.exit(0)
    end
end

host = "www.w3.org"
get(host, "/TR/html401/html40.txt")
get(host, "/TR/2002/REC-xhtml1-20020801/xhtml1.pdf")
get(host, "/TR/REC-html32.html")
get(host, "/TR/2000/REC-DOM-Level-2-Core-20001113/DOM2-Core.txt")
dispatch()