-- load our favourite library

local dispatch = require("dispatch")

local handler = dispatch.newhandler()

-- make sure the user knows how to invoke us

if #arg < 1 then

    print("Usage")

    print("    lua forward.lua <iport:ohost:oport> ...")

    os.exit(1)

end

-- function to move data from one socket to the other

local function move(foo, bar)

    local live

    while 1 do

        local data, error, partial = foo:receive(2048)

        live = data or error == "timeout"

        data = data or partial

        local result, error = bar:send(data)

        if not live or not result then

            foo:close()

            bar:close()

            break

        end

    end

end

-- for each tunnel, start a new server

for i, v in ipairs(arg) do

    -- capture forwarding parameters

    local _, _, iport, ohost, oport = string.find(v, "([^:]+):([^:]+):([^:]+)")

    assert(iport, "invalid arguments")

    -- create our server socket

    local server = assert(handler.tcp())

    assert(server:setoption("reuseaddr", true))

    assert(server:bind("*", iport))

    assert(server:listen(32))

    -- handler for the server object loops accepting new connections

    handler:start(function()

        while 1 do

            local client = assert(server:accept())

            assert(client:settimeout(0))

            -- for each new connection, start a new client handler

            handler:start(function()

                -- handler tries to connect to peer

                local peer = assert(handler.tcp())

                assert(peer:settimeout(0))

                assert(peer:connect(ohost, oport))

                -- if sucessful, starts a new handler to send data from

                -- client to peer

                handler:start(function()

                    move(client, peer)

                end)

                -- afte starting new handler, enter in loop sending data from

                -- peer to client

                move(peer, client)

            end)

        end

    end)

end

-- simply loop stepping the server

while 1 do

    handler:step()

end