Question

for (count = index, packet_no = 0; 
     count < TOTAL_OBJ, packet_no < TOTAL_PKT; 
     count++, packet_no++)

=> left-hand operand of comma expression has no effect.

I find the above code is correct and could not understand why this error comes.

Answer 1

This is how the comma operator works, what you want to do is to use OR or AND (probably AND in your case):

// the condition for resuming the loop is that one of the conditions is true
count < TOTAL_OBJ || packet_no < TOTAL_PKT
// the condition for resuming the loop is that both conditions are true
count < TOTAL_OBJ && packet_no < TOTAL_PKT