LuaAsio

Simple transparent non-blocking, high concurrency I/O for LuaJIT. Only 600+ lines.

There are no callbacks, Asynchronous happens when you perform a non-blocking operation.

Lightweight, low resource usage, available for embedded devices.

Based on Boost.Asio (Header-only) Library.

Tested on windows, ubuntu, openwrt.

Usage

Server side:

local asio = require 'asio'

function connection_th(con)
    -- Issues a synchronous, but non-blocking I/O operation.
    local data = con:read(5)
    -- Still non-blocking
    con:write(data .. '-pong')
    con:close()
end

local s = asio.server('127.0.0.1', 1234, function(con)
    -- light threads running asynchronously at various I/O operation.
    asio.spawn_light_thread(connection_th, con)
end)

-- This event loop is blocked during code execution
asio.run()

Client side:

local asio = require 'asio'

local ping_send = function(text)
    local con = asio.connect('localhost', '1234')
    con:write(text)
    con:read(10)
    con:close()
end

asio.spawn_light_thread(ping_send, 'ping1')
asio.spawn_light_thread(ping_send, 'ping2')

asio.run()

Light Thread & non-blocking

Your code needs to execute in Light Thread, actually Light Threads are Lua coroutine that all running in one thread, so you don't have to worry about context switching overhead and race conditions.

When goes to a non-blocking operation, the current Light Thread will wait for completion (block), and then it switches to the other available Light Thread to continue execution, or handle new connection.

If you want to use multithreading, Client side can be simply achieved by multiple Lua State (use like torch/threads); Server side not supported yet, but easy to implement by Lua State pool. Although because non-blocking, there is high concurrency even in a single thread.

Example: Real Case

Full duplex Transparent Proxy for Router

Big effect, so simple!

Client/Router:

-- you should replace the following with aes_256_cfb8 by require "resty.aes"
local bit = require 'bit'
local function xor_str(str, key)
    local rtn = table.new(#str, 0)
    for i = 1, #str do
        rtn[#rtn + 1] = string.char( bit.bxor(string.byte(str, i), key) )
    end
    return table.concat( rtn )
end

function forward(from_con, to_con)
    while true do
        local data, rerr, werr, _
        data, rerr = from_con:read_some()
        if data and #data > 0 then
            _, werr = to_con:write(xor_str(data, 0x79))
        end
        if rerr or werr then break end
    end
    from_con:close()
    to_con:close()
end

local asio = require 'asio'

function connection_th(upstream)
    local dest_addr = upstream:get_original_dst()
    local proxy = asio.connect(remote_host, remote_port)
    if not proxy then return end
    local ok = proxy:write(xor_str(dest_addr, 0x79))
    if not ok then return end
    asio.spawn_light_thread(forward, proxy, upstream)
    asio.spawn_light_thread(forward, upstream, proxy)
end

local s = asio.server('0.0.0.0', local_port, function(upstream)
    asio.spawn_light_thread(connection_th, upstream)
end)

asio.run()

Server:

local asio = require 'asio'

function connection_th(upstream)
    local dest_addr = upstream:read(128)
    if not dest_addr then return end
    local downstream = asio.connect(xor_str(dest_addr, 0x79))
    if not downstream then return end
    asio.spawn_light_thread(forward, downstream, upstream)
    asio.spawn_light_thread(forward, upstream, downstream)
end

local s = asio.server(listen_host, listen_port, function(upstream)
    asio.spawn_light_thread(connection_th, upstream)
end)

asio.run()

Finally, you need to use iptables redirect tcp to the client, and use https-dns-proxy to convert dns from udp to tcp.

Building

Windows

./build.bat

Linux

./build.sh

ARM Cross Compile

./build_arm.sh

Unit Test

./test/luajit ./test/test.lua

Reference

holder = asio.server(ip, point, accept_handler)

Listening port starts accepting connections.

accept_handler(conn) is your callback function when new connection is established. If you want to perform non-blocking operations on conn, you need call spawn_light_thread first.

Server are automatically closed when the return value holder are garbage collected.

---

conn, err_msg = asio.connect(host, port, resolve_v6=false)

Connect to the host port. This is a non-blocking operation.

Resolve host name is not a non-blocking operation yet, So use IP address.

If there are no errors, return conn(module); otherwise, returns nil, err_msg(lua str).

---

conn, err_msg = asio.connect(sockaddr_storage)

Same as connect(host, port). sockaddr_storage is return value of conn:get_original_dst().

---

asio.sleep(sec)

Suspends the execution of the current light thread until the duration have elapse. This is a non-blocking operation.

---

data, err_msg = conn:read(size)

Read binary data of a specified size. This is a non-blocking operation.

If there are no errors, return data(lua str); otherwise, returns nil, err_msg(lua str).

---

data, err_msg = conn:read_some()

Read binary data until one or more bytes. This is a non-blocking operation.

If there are no errors, return data(lua str[size>0]); otherwise, returns data(lua str[size>=0]), err_msg(lua str).

---

ok, err_msg = conn:write(data)

Write the data(lua str) to connection. This is a non-blocking operation.

If there are no errors, return true; otherwise, returns nil, err_msg(lua str).

---

nil = conn:close()

Close a connection. No returns.

---

asio.spawn_light_thread(function, arg1, arg2, ...)

Create and run a light thread.

License

LuaAsio is available under the MIT license.

Copyright (C) 2018, by Jianhao Zhang (Heerozh) (heeroz@gmail.com), All rights reserved.