From: Robert Klemme <shortcutter@...>
Date: 2012-08-20T18:02:22+09:00
Subject: Re: TCPserver how to signal EOT

On Sun, Aug 19, 2012 at 1:03 PM, tammy roberts <lists@ruby-forum.com> wrote:
> Hi I am writing some networking code and am having a heck of a time
> figuring out how to break on EOT.

> This is only one of
> many ways I have tried, client.recvfrom does not seem to return 0 or -1
> when no more data is to be sent, it also does not seem to return an
> empty string.

Then it probably blocks.

> Pretty much the only way I have gotten this to work is by
> looping client.recvfrom and then breaking if the character at -1 in what
> it gets is the ASCII control character for EOT. Unfortunately I can not
> use that because when I send random binary data there is a chance it
> will end on EOT without it being a control character.

I have seen recvfrom mainly used with UDP sockets and I am not sure
whether it blocks.  Apparently you want blocking behavior since you
create a thread per connection.

> Surely there is some easy way to do this, but none of the Ruby
> documentation mentions anything about how to and most of the examples do
> not even have recv in a loop for some reason.

Yes, just use Ruby's ways to use custom line delimiters.  Here's one
working way:

DELIMITER = "\x04".freeze

loop do
  Thread.new(server.accept) do |client|
    printf "Client %p START\n", client

    client.each_line DELIMITER do |msg|
      printf "msg len = %4d msg: %p bytes: %p\n", msg.length, msg,
msg.unpack('C*').map {|i| "%02x" % i}
      msg.chomp! DELIMITER
      printf "msg len = %4d msg: %p bytes: %p\n", msg.length, msg,
msg.unpack('C*').map {|i| "%02x" % i}
    end

    printf "Client %p STOP\n", client
  end
end

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/