From: Brian Candler <B.Candler@...>
Date: 2003-07-01T05:17:00+09:00
Subject: Re: Does Threading work properly?

On Tue, Jul 01, 2003 at 02:07:14AM +0900, kingsley@icecode.org wrote:
> require \'net/telnet\'
> require \'thread\'

Why do you keep putting these backslashes in? It means your code can't be
pasted in and run :-(

> thr4 = Thread.new() do
> loop do
> tn.cmd(gets.chomp) { |str| print str }
> end
> end
> 
> thr3 = Thread.new() do
> loop do
> tn.waitfor(\"Match\" => /.+/) { |str| print str }
> end
> end

I have never used the telnet module you are talking about; are you sure it's
thread-safe? (i.e. you can simultaneously call "cmd" and "waitfor" on a
single instance?)

Looking at the documentation in the pickaxe, it looks like you're using it
in the wrong way: if you pass a block to Telnet#cmd then that block receives
the results from the server. Hence you have two threads simultaneously
trying to read responses from the server, which seems like a bad thing to
me.

You'd need to do something like:

  line = gets.chomp
  tn.cmd( {'String'=>line, 'Match'=>/.+/, Timeout=>5} )

But even that's wrong, because the server could generate multiple responses
to one command, but your match on /.+/ would catch only the first response.
In other words, the telnet class is only really useful if you know what
response to expect from each command. It's a kind of poor-man's "expect".

Personally I think you'd be better of with a raw socket, because then you
definitely _can_ send and receive simultaneously:

require 'socket'
require 'thread'

sock = TCPSocket.new('ftp.tiscali.nl',21)

t1 = Thread.new do
  while line = gets
    sock.write line
  end
end
t2 = Thread.new do
  while ch = sock.read(1)
    putc ch
  end
end
t1.join
t2.join

The only thing to beware of is that a true telnet server may send some odd
escape sequences as it tries to negotiate some telnet options, but apart
from that the above should be fine as a simple telnet client.

Regards,

Brian.