From: Tanaka Akira <akr@...17n.org>
Date: 2004-03-27T21:17:59+09:00
Subject: Re: non blocking read and thread

In article <000001c413d5$e0ec97a0$0300a8c0@boulba>,
  "yannick" <yannick@dazzlebox.com> writes:

> Thank you for the tip, using sysread does fix this problem. But after
> further tests, I found another problem. Apparently, as Ara.T.Howard
> pointed out before, Kernel#select and IO#sysread seems to be a bad mix.
> Every sockets Kernel#select returns seems to be buffered, as this code
> shows :

The problem is not Kernel#select but IO#eof?.
IO#eof? is a kind of buffered IO methods.

EOF should be detected using EOFError caused by sysread.

        require 'socket'
        require 'fcntl'
        Thread.new do
                sleep 2
                client = TCPSocket.new('localhost', '1999') 
                loop do
                        sleep 1
                        client.syswrite "message"
                end
        end
        server = TCPServer.new("0.0.0.0","1999")
        thr = Thread.new do
                socks = []
                loop do
                        rs,wd,ed = select(socks+[server],nil,nil)
                        rs.each do |sock|
                                if sock == server
                                        n_sock = server.accept
                                        n_sock.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK)
                                        socks.push n_sock
                                        #This call will not raise an IOError
                                        #because this socket in not buffered yet.
                                        puts n_sock.sysread(100)
                                elsif sock.closed?
                                        socks.delete sock
                                else
                                        #This call however will raise an IOError.
                                        begin
                                                puts sock.sysread(100)
                                        rescue EOFError
                                                sock.close
                                                socks.delete sock
                                        end
                                end
                        end
                end
        end
        thr.join
-- 
Tanaka Akira