RE: Using luasocket to read from the keyboard

[<adimurthy.sriramulu@...>]

Hi All,

I will be working on LUA Sockets,pls let me know what are the libraries
I have to include and some sample programs on LUA Socket programming.


-Adi 

-----Original Message-----
From: lua-bounces@bazar2.conectiva.com.br
[mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Nick Gammon
Sent: Friday, June 06, 2008 6:00 AM
To: Lua list
Subject: Using luasocket to read from the keyboard

Hello all,

I am trying to write a Lua application that reads, asynchronously, from
both a TCP/IP connection, and the keyboard, much like telnet does.
Specifically, I want to pause on the "select" statement and await either
data from the host, or something typed by the user.  
However I am having trouble getting it to work.

A small application written in C works, as you can supply standard file
descriptors, something like this:

     FD_ZERO( &in_set  );
     // add our socket
     FD_SET( s, &in_set  );
     // and stdin
     FD_SET( STDIN_FILENO, &in_set  );
     if (select (UMAX (s, STDIN_FILENO) + 1, &in_set, NULL, NULL,
&timeout) == 0)
       return 0;


However my attempts to emulate this behaviour in luasocket have been
unsuccessful.

The closest I get is this:

-----------
require 'socket'

-- TCP connection to server
conn = assert (socket.connect("localhost", 4000))

-- keyboard input 'socket'
keyboard = socket.tcp ()
keyboard:close ()
keyboard:setfd (0)  -- I Googled setfd for this idea  (STDIN is
descriptor 0)

recvt = { conn, keyboard }

while true do

  readable, writable, error = socket.select(recvt, nil , 10)
  print "got past select"

  if readable [conn] then
    s = conn:receive (100)
    io.write (s)
  end -- if

  if readable [keyboard] then
    print "got keyboard input"
--   s = assert (keyboard:receive (100))
    s = io.read (10)
    io.write (s)
  end -- if

end -- while
---------------

Assuming there is a server to connect to at port 4000, this code
successfully displays the welcome message from the server, but ignores
any typing on the keyboard.

However if you change the select to only look at the keyboard, namely:

recvt = { keyboard }


Then it will work in a fashion. It detects keyboard input, once you
press <enter>, but only returns the first 10 characters each time
through the loop. That is, you get 10 characters every 10 seconds. If I
make it io.read (100) it returns nothing until 100 characters are typed.

If I change the code from io.read (10) to keyboard:receive (100) I get
this error message:

   calling 'receive' on bad self (tcp{client} expected, got userdata)

Somehow I think I am doing this wrongly, and any suggestions from the
luasocket experts are welcome. :-)

- Nick


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