handle AVL messages with iodine

Question

Right now I'm developing a some sort of parser for the messages of the Skypatrol TT8750+ and my threaded TCP server is working. The problem is that it isn't a good approach if there are to many devices connected at the same time. I'm using iodine but I can't make work some code that was given to me. My goal is to receive first a 33bytes message to identify the device and then start to receive 86bytes messages with information of the vehicle.

require 'iodine'

# define the protocol for our service
class TT8750plus
  @timeout = 10
  def on_open
    puts "New Connection Accepted."
    # this file is just for testing purposes.
    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
      po += @expecting
      @expecting = 86
      @msg.clear
    end
    if(length > 0)
      @msg << (buffer[pos, length])
      @expecting = 86 - length
    end
    puts @msg
  end

  def on_close
    @out_file.close
  end
end
# create the service instance
Iodine.listen 12050, TT8750plus
# start the service
Iodine.start

And this error appears on every message

New Connection Accepted.
Iodine caught an unprotected exception - NoMethodError: undefined method `+' for nil:NilClass
iodineServer.rb:26:in `on_message'
iodineServer.rb:1:in `on_data'Iodine caught an unprotected exception - NoMethodError: undefined method `+' for nil:NilClass

Also this implementation doesn't get the messages I need These are the first two lines that I got from this implementation:

0021000a0800000000000120202020202038363332383630323034333433373020
0021000a08000000000001202020202020383633323836303230343334333730200056000a08100020202020202038363332383630323034333433373020014b0000

And these are the first two lines from the threaded implementation

0021000a0800000000000120202020202038363332383630323034333433373020
0056000a08100020202020202038363332383630323034333433373020000b00000013090044709bfb8109e400000000001100000000000067eb11090c1512012e970020000000000005000000000005000000000007 
0056000a08100020202020202038363332383630323034333433373020010b00000013090044709bfb8109e400000000001200000000000067eb11090c1512042e970020000000000005000000000005000000000008

Answer 1

This looks like a variation of the untested code I posted earlier.

It seems the issue is with a spelling mistake in the code (probably mine?).

The po += ... should have been pos += ...

require 'iodine'

# define the protocol for our service
class TT8750plus
  @timeout = 10
  def on_open
    puts "New Connection Accepted."
    # this file is just for testing purposes.
    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 # the spelling mistake was here
      @expecting = 86
      puts "wrote:", @msg
      @msg.clear
    end
    if(length > 0)
      @msg << (buffer[pos, length])
      @expecting = 86 - length
    end
    puts("Waiting for more data:", @msg) unless @msg.empty?
  end

  def on_close
    @out_file.close
  end
end
# create the service instance
Iodine.listen 12050, TT8750plus
# start the service
Iodine.start

Again, lacking an emulation for the Skypatrol TT8750+, I can't test the code. But it should be possible to follow error messages to slowly track down these types of issues.

P.S.

To protect from exceptions, consider using Ruby's:

begin
    # code
rescue => e
    # oops something happened. i.e.
    puts e.message, e.backtrace
end

i.e., the on_message method might look like this:

  def on_message buffer
   begin
    length = buffer.length
    pos = 0
    while length >= @expecting
      @msg << (buffer[pos, @expecting])
      @out_file.puts(@msg.unpack('H*')[0])
      length -= @expecting
      pos += @expecting # the spelling mistake was here
      @expecting = 86
      @msg.clear
    end
    if(length > 0)
      @msg << (buffer[pos, length])
      @expecting = 86 - length
    end
    puts @msg unless @msg.empty? # print leftovers for testing...?
   rescue => e
     # oops something happened. React
     puts e.message, e.backtrace
   end
  end

Also, FYI, iodine allows you to control the number of processes (workers) and threads you'r using. See the documentation for details.