Lua Remote Procedure Call Protocol (draft)
------------------------------------------
 
All LuaRPC servers listen for connections on some sort of transport that reads
and writes bytes. Only one connection is accepted at a time, as the function
server only runs single threaded Lua code. Multiple servers may run on a
single computer, as long as they use different ports.
 
When an external client opens a connection, it can send function invocation
data. Multiple function invocations can be sent before the connection is
closed. Each function call has a set of return values that are returned to
the caller. On the client side, function calls that require no return
variables may be executed asynchronously.
 
`function' and `userdata' types can not be passed over the connection.
(a future option should allow this, one can already send functions as strings)
 
Protocol Definition
-------------------
 
session:
	u8 (03)				-- send command to exchange headers
	"LRPC"				-- "lua remote function protocol"
	u8						-- protocol version
	command, command, command, ...
	<end_of_file>
 
command:
	u8						-- command type (RPC_CMD_*)
									 01 - function_call
									 02 - get remote variable
									 03 - exchange header credentials
 
function_call:
	string				-- name of function
	u32						-- number of input variables
	var,var,...		-- input arguments
 
return_value:		-- normal return value
	u8 (0)
	u32						-- number of output variables
	var,var,...
 
return_value:
	u8 (1)				-- error return
	u32						-- error code
	string				-- error string
 
var:
	u8						-- type
	data...
 
string:	
	u32						-- length
	u8,u8,u8...		-- string bytes