Re: modularizing lua code

[Diman Todorov <diman@...>]

> 3) It doesn't have ping functionality, though it wouldn't be hard to
> do that, but why not? Pings that timeout are basically the only way I
> can think of to check if the network is available or not.

You can try to connect to a TCP port. If you get a connection, then the
host is up. If you get a 'port is closed' then the host is up. If you  
get
a timeout then the host is either behind a firewall or down.
While ICMP echo requests are useful, paranoid system administrators  
often
block them for no particular reason. As a matter of fact network probing
utilities like Nmap never completely rely on ICMP for host discovery.
I am attaching some LuaSocket sample code to demonstrate the idea.

cheers
Diman

<snip>
local socket = require("socket")

host = host or "127.0.0.1"
port = port or 80
if arg then
	host = arg[1] or host
	port = arg[2] or port
end

local isup

local c = socket.tcp()
c:settimeout(1)
local status, err = c:connect(host, port)

if(status == 1) then
	isup = true	
	c:close()
elseif string.match(err, "connection refused") then
	isup = true
elseif string.match(err, "timedout") then
	isup = false
end

if isup then
	print(host .. " seems to be up.")
else
	print(host .. " seems to be down.")
end

</snip>