I created a TCPServer with ruby gserver.
Everytime I connect remotly to the server, it takes 2-4 seconds until connection is established.
This is only happen if I connect from remote machine.
Connection from same machine has running the service will send immidiate response.
For the connection on same machine there is no difference if I connect via localhost or via the machines ip.
I think delay depends on reverse lookup but can not localize why.
in gserver.rb it is line 263
client = @tcpServer.accept
Here the delay occurs, I do not know what is in this method.
I added all machines which are used during tests to the local hosts file. But that changed nothing.
Same happens when using Webrick, I tried to set also
BasicSocket.do_not_reverse_lookup = true
as well as direct on the resulting server socket
Socket.do_not_reverse_lookup = true
as well as on client connection socket
client.do_not_reverse_lookup = true
But that also changed nothing on delay.
Whenever connection is established, the values of remote_host and remote_ip are resolved and as defined in hosts file.
I tried that running ruby 2.2.1 on ubuntu 14.04 as well as ruby 1.9.3 running debian wheezy.
Same behavior - (long) delay on connecting service.
Q: How to fix that / disable lookup on TCPServer?
The problem depends on my client machine where I run on MAC OSX Mav.
The used telnet client tries to open IPv6 connection and afterwards IPv4.
To solve the delay, just open connection with
telnet -4 my-server 3333
I have build a small connect echo servive where you can check resolves and timings.
If you change NO_REVERSE_LOOKUP you will get IPs or ADDRESSes and if not resolveable, different response times.
require 'socket'
NO_REVERSE_LOOKUP = true
CONNECT_PORT = 3333
puts "#{Time.now} Starting service on port: #{CONNECT_PORT}"
# the full hell - just to test if anything meets what we want
TCPServer.do_not_reverse_lookup = NO_REVERSE_LOOKUP
BasicSocket.do_not_reverse_lookup = NO_REVERSE_LOOKUP
Socket.do_not_reverse_lookup = NO_REVERSE_LOOKUP
srv = TCPServer.open(CONNECT_PORT)
puts "#{Time.now} Waiting for client"
client = srv.accept
puts "#{Time.now} Client connected"
client.do_not_reverse_lookup = NO_REVERSE_LOOKUP
client.print "Hello connected\n"
# in case that we disabled reverse lookup, we should only receive IP Adresses
puts "#{Time.now} Getting server address infos"
puts "SERVER INFO:"
puts NO_REVERSE_LOOKUP ? client.addr(:numeric) : client.addr(:hostname)
puts ""
puts "#{Time.now} Getting remote client infos"
puts "REMOTE INFO:"
puts NO_REVERSE_LOOKUP ? client.peeraddr(:numeric) : client.peeraddr(:hostname)
###
puts "#{Time.now} Closing connection"
client.close
puts "#{Time.now} End"
Thanks to drbrain from #ruby-lang irc for pointing me to the IPv6 problem.