test_mb.py

import telnetlib
import time

def read_header(tn):
	tn.read_until("\n", 1)

def twos_complement(input_value):
	return (~input_value +1) & 0xFF

def mbascii_request(payload):
	record = bytearray.fromhex(payload)
	record.append(twos_complement(sum(record)))
	return ":%s\r\n" % ''.join("%02X" % b for b in record)

def mbascii_response(payload):
	return bytearray.fromhex(payload[2:-4])


def mbascii_dorequest(tn, mb_request):
	print "TX:%s" % mb_request
	tn.write(mbascii_request(mb_request))
	status, obj, response = tn.expect([r"\r\n"], 5)
	if status == -1:
		print "failed to get response"
		return False
	print "RX:%s" % mbascii_response(response)
	return True


tn = telnetlib.Telnet('localhost', 10000)
#tn.set_debuglevel(1)

read_header(tn)

mbascii_dorequest(tn, '01050002FF00') #set 3rd coit ON
mbascii_dorequest(tn, '010100000008') #read first 8 coils