tcp - Ruby: TCPServer is not seeing that client TCPSocket has closed

Question

While running a TCPServer in ruby 2.7.0, I want to see when my client has closed the connection (or is unable to continue reading). However, when I check on the server, I never see that the connection has closed.

I've tried using a bunch of the different ruby socket primitives but nothing seems to work here. I've tried writing to the socket as well in hopes of forcing an error but that doesn't seem to help.

I'm including an example here:

# main.rb

require_relative 'server'

PORT = 9000

server_thread = Server.thread
socket = TCPSocket.open("localhost", PORT)
socket.puts '5'
server_thread.join(1)
socket.close
puts socket.closed?
server_thread.join(2)

# server.rb

require 'socket'

class Server

  def self.thread
    Thread.new do
      server = TCPServer.open(PORT)
      while true
        server.accept do |socket|
          while true
            socket.puts '1'
            # why doesn't this ever happen?
            puts 'closed' if socket.closed?
          end
        end
      end
    end
  end
end

When running ruby main.rb, this code outputs

true

Whereas I expect it to output:

true
closed

question from:https://stackoverflow.com/questions/65874447/ruby-tcpserver-is-not-seeing-that-client-tcpsocket-has-closed

Answer 1

1. The block that you pass to server.accept is ignored because Socket#accept does not accept a block argument.

2. When you call socket.close in main.rb, you close the client side of the connection. The server side of the connection will remain open.

   You could call IO#read to wait until the client closes the connection.

   Thread.new do
     server = TCPServer.open(PORT)
     loop do
       socket = server.accept
       socket.read
       puts 'client closed connection'
       socket.eof? #=> true
       socket.close
     end
   end