How do I calculate correct checksum for FIX messages?

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The following code is getting successful LOGON messages, but when i send quote-request in the 2nd message, its not replying & sending me a heartbeat after 30 seconds.Someone told me i'm not correctly calculating checksum, so that's why Fix-server ignoring the price-request message.Can you give me any clue why it's not working for the 2nd message?

What I have tried:

public static int total;

time = DateTime.UtcNow.ToString("yyyyMMdd-HH:mm:ss.fff");

                                body = "35=V|49=" + FixID + "|56=CSERVER|34="+msgSeqenceNum+"|52=" + time + "|50=QUOTE|57=QUOTE|262=13203481x|263=1|264=1|265=1|146=1|55=1|267=2|269=0|269=1|";

                                // body length
                                bodylen = body.Length;
                                string fix = "8=FIX.4.4|9=" + bodylen + "|";

                                // message
                                message = fix + body;

                                message = message.Replace('|', '\u0001');
                            int total2 = 0;
                                messageBytes = Encoding.ASCII.GetBytes(message);//converted to 0's &1s
                                for (int i = 0; i < message.Length; i++)
                                    total2 += messageBytes[i];

                                checksum = total2 % 256;
                                checksumStr = checksum.ToString().PadLeft(3, '0');

                                sum = "10=" + checksumStr + "|";
                                m = fix + body + sum;
                                m = m.Replace('|', '\u0001');

Posted 27-Mar-17 20:41pm

Viswash Manik

Updated 27-Mar-17 22:03pm

v2

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Graeme_Grant 28-Mar-17 2:56am

What does the host service documentation say regarding the calculation?

Viswash Manik 28-Mar-17 3:49am

Hi Graeme, the checksum value was calculated as per standard FIX-guidelines.

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Garth J Lancaster · Answer 1 · 2017-03-27T21:12:00

Quote:
Can you give me any clue why it's not working for the 2nd message?

look where you have 'total' defined .. do you reset the value of total before you get the checksum for your second message ?

I would break out this code, to get the checksum

C#

message = message.Replace('|', '\u0001');
 byte[] messageBytes = Encoding.ASCII.GetBytes(message);
 for (int i = 0; i < message.Length; i++)
 total += messageBytes[i];

 int checksum = 0;
 foreach (byte chData in messageBytes)
 {
     checksum += chData;
 }

 checksum = total % 256;
 string checksumStr = checksum.ToString().PadLeft(3, '0');

into a separate function/procedure/method - you repeat the code, real bad idea - if you break that code out of each location you can then go

C#

checksumStr = getChecksum(message);

for example .. then you can remove this disaster

Quote:
public static int total;

from your client

While I'm here, I'll throw in my 2 cents worth on building messages like that by concatenating strings - its barely ok for a test - I'd expect someone working for me to make a message builder class, for each type of message (so it starts as an abstract class), that you pass the values to it and it builds the message nicely - your messages as they are are hard to extend, debug etc - I guess you're lucky you're not working for me :)