From: "Iñaki Baz Castillo" <ibc@...>
Date: 2010-01-12T20:41:47+09:00
Subject: Re: How to close a TCP socket? (TCPSocket#close doesn't close it)

El Martes, 12 de Enero de 2010, Iñaki Baz Castillo escribió:

> > The TCP connection is terminated when you call TCPSocket#close.
> 
> Yes, I'm realizing of it right now. There must be some error in my code
>  which prevents the socket from being closed. I must investigate it.

I've found the cause of my issue. My ruby script listens into a pipe and when 
a message is received it's sent via the TCPSocket.
Also there is a thread which does @socket.gets("\r\n") to receive the 
responses. In this way I can I can send multiple requests to the server 
without waiting for the responses. Instead the thread doing "gets" reads the 
responses, parses a request identifier and that's all.

But in this case when calling socket.close the connection is not terminated. A 
simplified code:

  require "socket"
  @socket = TCPSocket.new(server, port)
  
  Thread.new do
    res = @socket.gets("\r\n")
  end
 
  @socket.close
  sleep 120


When "@socket.close" is called it's just closed "at Ruby level", this is, I 
cannot write/read from it as I get "closed pipe" error (which makes sense).

However the TCP connection remains open at OS level (in ESTABLISHED status as 
netstat shows in both the client and server).


But it's really interesting (for me) the following fact:

Without the line @socket.close netstat output shows (during the sleep 120):

  tcp  0  0 192.168.1.10:51112  88.231.79.226:5062  ESTABLISHED 23814/irb
  
But when running the script with @socket.close line then I see:

  tcp  0  0 192.168.1.10:51112  88.231.79.226:5062  ESTABLISHED -

It's like if the Ruby process (irb) has detached itself from the socket (no 
process pid in the netstat output for that connection), but the socket remains 
open at OS level.

Is it the expected behavior?

Thanks.

-- 
Iñaki Baz Castillo <ibc@aliax.net>