Small buffer receiving set of functions

server.lua

require 'socket'
require 'struct'

-- TODO: make class

print "Initializing server..."
server = socket.tcp()
server:bind('*',12312)
server:listen(32)
client = server:accept()
print "Server has been initialized!"
buffer = ""

function get_size()
  local header_length = 4
  --  local buffer = ""
  while string.len(buffer) < header_length do
     print("receiving size!")
     buffer = buffer .. client:receive(4)
  end
  local header = string.sub(buffer, 1, 5)
  buffer = string.sub(buffer, 5)
  buffer_length = struct.unpack('>I4', header)
  -- buffer = string.sub(buffer, header_length)
  -- print(buffer)
  return buffer_length
end

function get_packet()
  buffer_length = get_size()
  print("Size: ", buffer_length)
  -- buffer = ""
  while string.len(buffer) < buffer_length do
    buffer = buffer .. client:receive(buffer_length)
  end
  local s = string.sub(buffer, 1, buffer_length+1)
  buffer = string.sub(buffer, buffer_length+1)
  return s
end

function get_image()
  image_width = get_size()
  image_height = get_size()
  last_size = get_size()
  print("Size: ", last_size)
  -- buffer = ""
  while string.len(buffer) < last_size do
    buffer = buffer .. client:receive(last_size)
  end
  local s = string.sub(buffer, 1, last_size+1)
  buffer = string.sub(buffer, buffer_length+1)
  return s
end


while true do
  local packet = get_packet()
  print(string.sub(packet, 1, 10))
  local image = get_image()
  print(string.sub(image, 1, 10))
end

client:close()