From: Brian Candler <B.Candler@...>
Date: 2002-12-14T08:46:39+09:00
Subject: Re: TCP Server

On Sat, Dec 14, 2002 at 12:20:29AM +0900, Shannon Fang wrote:
> I am learning how to use Ruby to write a TCP Server. I used the sample code 
> in PickAxe, it worked fine, but I have no idea how I can let the program 
> connect more than one client? Do I need to use thread?
> 
> Can anyone show me how to do this by writing a echo server which can 
> connect multiple clients?

In case it's any use, here are a few snippets of fake POP3 server I wrote a
while back.

Here was my first attempt: the POP3 server instance is represented by its
own object.

-------------------------------------------------------------------------
#!/usr/local/bin/ruby -w

class Testserver
  def initialize(session)
    @session = session
  end
  def run
    @session.print "+OK I am a fake POP3 server\n"
    while line = @session.gets
      case line
        when /quit/i
          break
        else
          @session.print "-ERR I don't understand #{line}"
      end
    end
    @session.print "+OK bye\n"
    @session.close
  end
end

require 'socket'
port = (ARGV[0] || 110).to_i
server = TCPServer.new('0.0.0.0', port)
while (session = server.accept)
  Thread.new do
    Testserver.new(session).run
  end
end
-------------------------------------------------------------------------

The messy thing with that is having to keep referencing the instance
variable for the TCPSocket every time you want to input or output.

I tried subclassing TCPSocket, but I couldn't work out how to convert the
TCPSocket returned by server.accept into an instance of the subclass.

In the end, the tidiest solution seemed to be to dynamically add a 'run'
method to each TCPSocket as it is created:

-------------------------------------------------------------------------
#!/usr/local/bin/ruby -w

module Pop3
  def run
    print "+OK I am a fake POP3 server\n"
    while line = gets
      case line
        when /quit/i
          break
        else
          print "-ERR I don't understand #{line}"
      end
    end
    print "+OK bye\n"
    close
  end
end

require 'socket'
port = (ARGV[0] || 110).to_i
server = TCPServer.new('0.0.0.0', port)
while (session = server.accept)
  session.extend Pop3
  Thread.new do
    session.run
  end
end

-------------------------------------------------------------------------

It might not be quite as efficient though, although I don't know how much
overhead is associated with extending an object in this way.

Hope this gives you something to play with...

Regards,

Brian.