minimal lan messager over udp

client.rb

require 'socket'
PORT = 12321
def process_message(message,packet_info)
  message = Marshal.load(message)
  case message[:type]
  when :broadcast
    return reply_broadcast(message,packet_info)
  when :reply
    return deal_reply(message,packet_info)
  when :message
    return display(message,packet_info)
  end
end
def reply_broadcast(message,packet_info)
  $ip_table[message[:message]] = packet_info[2]
  reply_msg = Marshal.dump({type: :reply,message: $name})
  UDPSocket.new.tap{|s| s.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1)}.send(reply_msg,0,'255.255.255.255',PORT)
end
def display(message,packet_info)
  puts "#{$ip_table.key(packet_info[2])}:#{message[:message]}"
end
def deal_reply(message,packet_info)
  $ip_table[message[:message]] = packet_info[2]
end
def init
  $name = 'unnamed'
  loop do
    puts 'your name?'
    $name = gets.strip
    message = Marshal.dump({type: :broadcast,message: $name})
    if message.length > 65535
      puts 'name is too long'
      next
    end
    UDPSocket.new.tap{|s| s.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1)}.send(message,0,'255.255.255.255',PORT)
    break
  end
end
$ip_table = {'broadcast'=>'255.255.255.255'}
socket = UDPSocket.new
Thread.new {
  socket = UDPSocket.new
  socket.bind('0.0.0.0',PORT)
  loop do 
    begin
      message = socket.recvfrom_nonblock(65535)
      process_message(*message)
    rescue Errno::EWOULDBLOCK#,Errno::AGAIN
      select([socket])
    end
  end
}

init
loop do 
  s = gets.strip
  s =~ /(.+?)\:(.+)/
  to = $1
  msg = $2
  if to.nil? or msg.nil?
    puts 'syntax error'
    next
  elsif $ip_table[to].nil?
    puts 'unknown user'
    next
  else
    message = Marshal.dump({type: :message,message: msg})
    if message.length > 65535
      puts 'message is too long'
      next
    end
  end
  UDPSocket.new.tap{|s| s.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1)}.send(message,0,$ip_table[to],PORT)
end