Ruby - ThreadError for Looping Connection - ruby

Question

I'm working on my first attempts on Sockets and Threading and am running into an issue where I believe I am hitting a thread cap, but not entirely sure.
Basically I have a server.rb which opens a TCPServer and a game.rb which connects to the server. On the server, when the user connects I output some general information and then want to start reading data that is passed through from the game.rb. I believe the problem I am running into is I am just creating a new thread everytime the loop executes and I think I'm meeting the cap. I am also not sure if this is best practice. I wanted to avoid using other APIs until I got a decent grasp on the basics, so I tried to follow the code from https://github.com/sausheong/tanks.
server.rb
require 'socket'
# lsof -i :2000
# kill ID
class Server
def initialize(host, port)
puts "starting arena"
#server = TCPServer.open(host, port)
#sprites = Hash.new
#players = Hash.new
handle_connection(#server.accept)
end
def handle_connection(socket)
_, port, host = socket.peeraddr
user = "#{host}:#{port}"
puts "#{user} has joined!"
puts "------"
loop do
thread = Thread.start(socket) do |client|
puts 'starting new thread'
data = socket.readpartial(4096)
data_array = data.split("\n")
if data_array && data_array.any?
begin
data_array.each do |row|
message = row.split("|")
puts message
end
rescue Exception => exception
puts "exception happened?"
puts exception.inspect
end
end
end
end # end loop
rescue EOFError => err
puts "error"
puts "Closing the connection. Bye!"
socket.close
puts err
end # handle_connection end
end # class end
Server.new('localhost', 2000)
game.rb
# create a server
# join server
# move Player
# communicate to server that player moved
# update players position for server?
require 'gosu'
require 'socket'
class Player
def initialize
#image = Gosu::Image.new("media/starfighter.bmp")
#x = #y = #vel_x = #vel_y = #angle = 0.0
#score = 0
end
def warp(x, y)
#x, #y = x, y
end
def turn_left
#angle -= 4.5
end
def turn_right
#angle += 4.5
end
def accelerate
#vel_x += Gosu.offset_x(#angle, 0.5)
#vel_y += Gosu.offset_y(#angle, 0.5)
end
def move
#x += #vel_x
#y += #vel_y
#x %= 640
#y %= 480
#vel_x *= 0.95
#vel_y *= 0.95
end
def draw
#image.draw_rot(#x, #y, 1, #angle)
end
end
class Client
def initialize(host, port)
#client = TCPSocket.open(host, port)
send_data("321|123")
end
def send_data(data)
#client.write(data)
end
# puts "enter your name:"
# client.write gets
#
# while line = client.gets
# puts line.chop
# end
end
class Tutorial < Gosu::Window
def initialize(server, port)
super 640, 480
self.caption = "Tutorial Game"
#client = Client.new(server, port)
#background_image = Gosu::Image.new("media/space.png", :tileable => true)
#player = Player.new
#player.warp(320, 240)
end
def update
if Gosu.button_down? Gosu::KB_LEFT or Gosu::button_down? Gosu::GP_LEFT
#player.turn_left
#client.send_data("left")
end
if Gosu.button_down? Gosu::KB_RIGHT or Gosu::button_down? Gosu::GP_RIGHT
#player.turn_right
end
if Gosu.button_down? Gosu::KB_UP or Gosu::button_down? Gosu::GP_BUTTON_0
#player.accelerate
end
#player.move
end
def draw
#player.draw
#background_image.draw(0, 0, 0)
end
def button_down(id)
if id == Gosu::KB_ESCAPE
close
else
super
end
end
end
Tutorial.new('localhost', 2000).show

Answer 1

Your loop: (simplified)
socket = #server.accept
loop do
Thread.start(socket) do |client|
# ...
end
end
accepts a single connection and then creates new threads as fast as it can, passing each thread the same socket object, so all of the threads start reading data from the same socket concurrently.
To avoid this, you have to move the accept call into the loop:
loop do
socket = #server.accept
Thread.start(socket) do |client|
# ...
end
end
Or simply:
loop do
Thread.start(#server.accept) do |client|
# ...
end
end
accept immediately blocks to wait for a new connection, effectively pausing the loop. Once a connection is established, it creates a new thread to handle that connection and the loop starts over.
A similar example can be found in the documentation for TCPServer.