Message size varies TCPServer Ruby - ruby

Question

I'm working with an AVL (Skypatrol TT8750+) and the messages that it sends (using TCP) are supposed to be 59bytes long but it always sends a first message (the message has some information about the AVL, so the user can identify it) of 33bytes.
So the question is, How can I handle those different size messages on ruby?
require 'socket'
portnumber = 12050
socketServer = TCPServer.open(portnumber)
while true
Thread.new(socketServer.accept) do |connection|
puts "Accepting connection from: #{connection.peeraddr[2]}"
t = Time.now.strftime("%d-%m-%Y %H%M")
file_name = t + '.txt'
out_file = File.new(file_name, "w+")
begin
while connection
incomingData = connection.gets()
if incomingData != nil
incomingData = incomingData
end
hex_line = incomingData.unpack('H*')[0]
out_file.puts(hex_line)
puts "Incoming: #{hex_line}"
end
rescue Exception => e
# Displays Error Message
puts "#{ e } (#{ e.class })"
ensure
connection.close
puts "ensure: Closing"
end
end
end
This is the experimental code that I'm using.

Answer 1

I'm posting this answer to explain a comment I made to Anderson's answer. Most of the code isn't mine.
moving the if out of the loop
When the if statement is within a loop, it will be evaluated each and every time the loop runs, increasing the number of CPU instructions and the complexity of each loop.
You could improve performance by moving the conditional statement out of the loop like so:
require 'socket'
require 'celluloid/io'
portnumber = 12050
socketServer = TCPServer.open(portnumber)
incomingData = nil
while true
Thread.new(socketServer.accept) do |connection|
puts "Accepting connection from: #{connection.peeraddr[2]}"
# this should probably be changed,
# it ignores the possibility of two connections arriving at the same timestamp.
t = Time.now.strftime("%d-%m-%Y %H%M")
file_name = t + '.txt'
out_file = File.new(file_name, "w+")
begin
if connection
incomingData = conection.recv(33)
if incomingData != nil
incomingData = incomingData.unpack('H*')[0]
out_file.puts(incomingData)
puts "Incoming: #{incomingData}"
end
end
while connection
incomingData = connection.recv(59)
if incomingData != nil
incomingData = incomingData.unpack('H*')[0]
out_file.puts(incomingData)
puts "Incoming: #{incomingData}"
end
end
rescue Exception => e
# Displays Error Message
puts "#{ e } (#{ e.class })"
ensure
connection.close
out_file.close
puts "ensure: Closing"
end
end
end
Optimizing the recv method
Another optimization I should probably mention (but won't implement here) would be the recv method call.
This is both an optimization and a possible source for errors that should be addressed.
recv is a system call and as network messages might be combined (or fragmented) across TCP/IP packets, it might become more expensive to call recv than to handle an internal buffer of data that resolved fragmentation and overflow states.
Reconsidering the thread-per-client design
I would also recommend avoiding the thread-per client design.
In general, for a small number of clients it probably doesn't matter much.
However, as clients multiply and threads become busier, you might find the system spends more resources on context switches than actual tasks.
Another concern might be the allocated stack each thread requires (1Mb or 2Mb for Ruby threads, if I remember correctly)... In a best case scenario, 1,000 clients will require more than a GigaByte of memory allocation just for the stack (I'm ignoring kernel structure data table and other resources).
I would consider using EventMachine or Iodine (I'm iodine's author, so I'm biased).
An evented design could save you many resources.
For example (untested):
require 'iodine'
# define the protocol for our service
class ExampleProtocol
#timeout = 10
def on_open
puts "New Connection Accepted."
# this should probably be changed,
# it ignores the possibility of two connections arriving at the same timestamp.
t = Time.now.strftime("%d-%m-%Y %H%M")
file_name = t + '.txt'
#out_file = File.new(file_name, "w+")
# a rolling buffer for fragmented messages
#expecting = 33
#msg = ""
end
def on_message buffer
length = buffer.length
pos = 0
while length >= #expecting
#msg << (buffer[pos, #expecting])
out_file.puts(msg.unpack('H*')[0])
length -= #expecting
pos += #expecting
#expecting = 59
#msg.clear
end
if(length > 0)
#msg << (buffer[pos, length])
#expecting = 59-length
end
end
def on_close
#out_file.close
end
end
# create the service instance
Iodine.listen 12050, ExampleProtocol
# start the service
Iodine.start

Answer 2

The solution was quite simple
require 'socket'
require 'celluloid/io'
portnumber = 12050
socketServer = TCPServer.open(portnumber)
while true
Thread.new(socketServer.accept) do |connection|
puts "Accepting connection from: #{connection.peeraddr[2]}"
t = Time.now.strftime("%d-%m-%Y %H%M")
file_name = t + '.txt'
out_file = File.new(file_name, "w+")
messagecounter = 1
begin
while connection
if messagecounter == 1
incomingData = conection.recv(33)
messagecounter += 1
else
incomingData = connection.recv(59)
end
if incomingData != nil
incomingData = incomingData.unpack('H*')[0]
end
out_file.puts(incomingData)
puts "Incoming: #{incomingData}"
end
rescue Exception => e
# Displays Error Message
puts "#{ e } (#{ e.class })"
ensure
connection.close
puts "ensure: Closing"
end
end
end
I just needed an extra variable and an if to auto increment the variable, and that's it.