Using luasocket to read from the keyboard

[Nick Gammon <nick@...>]

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