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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.


local socket = require("socket")

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

local isup

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

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

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