UDP in Ruby - packing socket manually

client.rb

# or `echo some-request | nc localhost 8181 -4u `
MAX_READ = 1024 * 8
FLAGS    = 0

c = Socket.new :INET, :DGRAM
s = Socket.pack_sockaddr_in 8181, "127.0.0.1"

c.send("some-request", FLAGS, s)

res = c.recv(MAX_READ)

server.rb

MAX_READ = 1024 * 8
FLAGS    = 0

trap(:INT) { exit }

s = Socket.new :INET, :DGRAM
a = Socket.pack_sockaddr_in 8181, "127.0.0.1"

s.bind(a)

loop do
  req, addr = s.recvfrom(MAX_READ)
  
  puts "server: #{req} from #{addr.inspect}"

  s.send("some-response", FLAGS, addr)
end