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I have an industrial sensor that via an Interface module provides raw values via telnet.

In order to connect to it:

 telnet 169.254.168.150 10001

I can only see garbage values from it.

Information

The information that I have is from the datasheet of the Interface module.

The sensor is an analog one, hence Status flag is not relevant.

I have some propreitary software from the company which visualizes the information of the sensor. This software also uses the above mentioned telnet protocol to obtain information. I cross checked it via WireShark. Packet size is 22 Bytes and in little-endian.

I cannot programatically obtain the information as my SE Query and I am looking to obtain the value maybe store the incoming values directly somewhere (in DB or file).

Is there any way to extract this infomation via the Command Line?

Extract from the pastebin:

00000050 2e 0a 53 41 45 4d 00 00 00 00 f6 04 00 00 15 00 |..SAEM..........|
00000060 00 00 00 00 00 00 00 00 00 00 0c 00 01 00 fa 94 |................|
00000070 00 00 8c 00 00 00 8c 00 00 00 0a 23 00 00 53 41 |...........#..SA|
00000080 45 4d 00 00 00 00 f6 04 00 00 15 00 00 00 00 00 |EM..............|

So this shows the information is all there, it's little endian, and you just have to read and parse them. Any tool you are confortable with will do; a C program, a perl program, anything you like. You may have to skip over the telnet output at the beginning, or use something else instead of telnet (e.g. nc, netcat, socat).

To demonstrate perl, to decode one packet, you'd do something like

cat ... | perl -nle "print join(':',unpack 'a4 (L2 Q L S2 l4)<')"

on the command line for the packet in the dump, and get as output

SAEM:0:1270:21:0:12:1:38138:140:140

This only works for the given number of channels (and the mask says that one of the four measurement values shouldn't be present, but it has a value; I don't understand that part).

If you get a variable number of channels depending on other information, you need smarter parsing.

So apparently I thought the other way round. Since I was capturing data on Wireshark all the packets were tcp and only the initial few packets were of telnet (session initiation information).

I decided to create a tcp socket using python and read the data of 22 bytes (size available from Wireshark Dump)

and I used struct module to unpack the information. Interesting was to find out that the useful sensor information came always as the alternate TCP payload i.e. First packet had only information like preamble, article number, serial number etc. and the next payload had all the information Counter, Channel 1 value, Channel 2 value, Channel 3 value

The information obtained here was in int32 which needs to converted to appropriate value using a formula mentioned in the module's instruction manual

Code

import socket
import struct

# CONSTANTS for Formula
# ....

# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server_address = ('169.254.168.150', 10001)
print('connecting to %s port %s' % server_address)
sock.connect(server_address)


def value_mm(raw_val):
""" Formula for conversion """
 return (((raw_val - DRANGEMIN) * MEASRANGE) / (DRANGEMAX - DRANGEMIN) + OFFSET)


if __name__ == '__main__':
 while True:
 Laser_Value = 0
 data = sock.recv(22)
 # First frame
 preamble, article, serial, x1, x2 = struct.unpack('<4sIIQH', data)

 # if this payload is not the preamble, it must be information payload
 if not preamble == b'SAEM':
 status, bpf, mValCounter, CH1, CH2, CH3 = struct.unpack('<hIIIII',data)
 #print(CH1, CH2, CH3)
 Laser_Value = CH3
 print(str(value_mm(Laser_Value)) + " mm")

 print('n')