Hi. I have a working ruby 2.7.2 app that is a simple udp server on my local development machine which uses the ruby UDPSocket library. I have created a ubuntu 18.04 droplet and created a cloud firewall with a custom inbound rule protocol:udp, port range:7373. I have created a non-sudo user (m32_udp) and placed the app in /var/www/m32_udp/code directory with these privilages.
m32_udp@megazoic:/var/www/m32_udp/code$ ls -l total 24 -rw-r–r-- 1 m32_udp m32_udp 60 Nov 11 22:56 Gemfile -rw-r–r-- 1 m32_udp m32_udp 100 Nov 11 23:51 Gemfile.lock -rw-r–r-- 1 m32_udp m32_udp 368 Nov 11 22:56 client.rb -rw------- 1 m32_udp m32_udp 115 Nov 12 01:14 nohup.out -rw-r–r-- 1 m32_udp m32_udp 2194 Nov 11 22:56 server.rb
My ruby code (abbreviated) is
@socket = UDPSocket.new @socket.bind("0.0.0.0", @port)
I have also tried entering my droplet’s ip address in the bind parameter. Also @port is 7373.
When I start the app as m32_udp user, netstat reports…
watchdog@megazoic:~$ netstat -an
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 188.8.131.52:22 184.108.40.206:59072 ESTABLISHED tcp 0 316 220.127.116.11:22 18.104.22.168:59064 ESTABLISHED tcp6 0 0 :::22 :::* LISTEN
udp 0 0 127.0.0.53:53 0.0.0.0:*
udp 0 0 0.0.0.0:7373 0.0.0.0:*
When I change the ruby code in my app to
udp 0 0 22.214.171.124:7373 0.0.0.0:*
In either case, I cannot see this port as being open using netcat from another machine. It is also not reported as LISTEN in netstat. Do I need to run this app with sudo privileges? Do I have the ip address correct in the bind statement? Thanks for any help that you can provide!
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My bad. This was working with the original socket.bind call using 0.0.0.0
I guess that I expected netstat to report LISTEN for this port as my app was indeed listening.
Thanks for looking