clientserver.lua

local protocol
local name

local function parse (str) 
	local f, args = nil, {}
	for token in string.gmatch(str, '[^|]+') do
		if not f then f = token else
			table.insert(args, token)
		end
	end
	return f, args
end


local clients = {}
local function client_up (sid, name)
	-- a new client comes to the network.
	rednet.send(sid, 'server_id|'..os.computerID(), protocol)
end

local function connect(sid, name)
	table.insert(clients, sid)
	print('Registered client:' .. sid .. ' name:' .. name)
	print('Total clients: ' .. #clients)
	rednet.send(sid, 'connect_done', protocol)
end

local server
-- server authoritative answer
local function server_up (sid)
	print('Server announcing, connecting to: ' .. sid)
	rednet.send(sid, 'connect|' .. name, protocol)
end
-- new client, inform of our server id
local function peer_up (sid)
	if server then
		print('Peer:'..sid..' is announcing.  Replying with server id:'..server)
		rednet.send(sid, 'server_id|' .. server, protocol)
	end
end
-- non-authoritatve answer, connect explicitely.
local function server_id (sid, serverId)
	if not server then
		print( 'Peer:' .. sid .. ' points to Server:' .. serverId);
		if tonumber(serverId) ~= os.getComputerID() then 
			local server = tonumber(serverId)
			print( 'Connecting to: ' .. server)		
			rednet.send(tonumber(server), 'connect|'..name, protocol)
		end
	end
end

-- server connect confirmation
local function connect_done (sid)
	server = sid
	print('Connected to server: ' .. sid)
end

local clientCommands = {
	server_up = server_up,
	client_up = peer_up,
	server_id = server_id,
	connect_done = connect_done
}

local serverCommands = {
	client_up = client_up,
	connect = connect
}

local function loop (commandTable, timerFunc, delay)
	assert(commandTable)
	while true do
		local sid, msg, p;
		if timerFunc then
			repeat
				sid, msg, p = rednet.receive(protocol, delay or 30)
				timerFunc()
			until sid
		else
			sid, msg, p = rednet.receive(protocol);
		end
		assert(p == protocol)
		--print('network: ' .. msg)
		cmd, args = parse(msg)
		local func = commandTable[cmd]
		if func then
			func(sid, unpack(args))
		end
	end
end

function addCommandTable (source, commands)
	if source == 'server' then
		for k,v in pairs(commands) do
			serverCommands[k] = v
		end
	end
end

function send (message)
	if server then
		rednet.send( tonumber(server), message, protocol);
	end
end

function run (role, _protocol, timerFunc, delay) 
	print( 'Client/Server - Sample' )
	print( 'We are computer: ' .. os.getComputerID())

	protocol = _protocol

	assert(role == 'client' or role == 'server', 'Specify "client" or "server"')
	assert(protocol, 'Specify a server')
	--assert(modemLocation == 'left' or modemLocation == 'right' 
	--	or modemLocation == 'top' or modemLocation == 'bottom'
	--	or modemLocation == 'front' or modemLocation == 'back', 'Specify side for the rednet conenction.');

	local modemLocation = peripheral.find('modem', function (n,o) return o.isWireless() end );
	modemLocation.open(os.getComputerID())
	modemLocation.open(65535)
	--rednet.open(modemLocation)

	if role == 'server' then
		local hosts = {rednet.lookup(protocol, 'server')}
		local thisAsHost = hosts[1] == os.computerID()
		assert(thisAsHost or 0 == #hosts, 'Another server exists.')
		name = 'server'
	else
		name = 'client-'..os.computerID()
	end
	rednet.host(protocol, name)
	print('Registered '..name..' on protocol '..protocol)

	if role == 'server' then
		-- collect existing clients
		print('Annoucing server on ' .. protocol)
		rednet.broadcast('server_up', protocol)
		print('Running...')
		loop(serverCommands, timerFunc, delay)
	else
		print('Announcing client on ' .. protocol)
		rednet.broadcast('client_up|'..name, protocol)
		print('Running...')
		loop(clientCommands, timerFunc, delay)
	end
end