A trivial story, which explains my trouble shooting against a small problem that happened in providing my lecture on "network technologies (1)/(2)"

1. A Story on Sinatra's F*cking
Confguration that Really,
Really Bothered Me!
1,000 speakers conference #6
Jun Iio

2. 1,000 speaker conf #6 Copyright © Jun Iio 2
Sinatra

3. 1,000 speaker conf #6 Copyright © Jun Iio 3
Problem
●
My lecture at Chuo University
– “Network Technologies (1)/(2)”
– A hands-on training course using “Sinatra”
●
Problem
– Sinatra is quite easy to build an application
– $ ruby main.rb [RET]
●
a web server runs... but is not accessible from
outside
– Only it can be accessed locally, so the hands-
on has to be conducted in a pseudo network
environment (in the last year's case)

4. 1,000 speaker conf #6 Copyright © Jun Iio 4
Problems in the net?
●
Routers (and its upstream) are concealed!
– Sinatra uses #4567 port in its default confg
– “Are there some bottlenecks in the net?”
?
Network conf. is
controlled by
IT-center

5. 1,000 speaker conf #6 Copyright © Jun Iio 5
Problems in the server?
●
Server confguration ?
– Server is running on Ubuntu 13.04
●
ufw (user frewall)
– 22(ssh), 80(http), … well known port … OK
– 4567 … NG!
●
NMAP (port scanning)
– “4567 is not open”

6. 1,000 speaker conf #6 Copyright © Jun Iio 6
Problems in the server?
●
$ netstat -l [RET]
…
tcp4 0 0 localhost.4567 *.* LISTEN
…
●
Umm? “localhost” ?

7. 1,000 speaker conf #6 Copyright © Jun Iio 7
The problem is in the APP!!