...
echo_reply = struct.unpack("qqibbHHhff", recPacket)			# the received packet is in binary format
# print(echo_reply)

icmp_header_index = 3                                    # at the 3rd index of received message starts ICMP type and code 
if isErrorInEcho(echo_reply[icmp_header_index], echo_reply[icmp_header_index + 1]):
	return "Error occurred."

# in binary format we read from recPacket into 2 floats but we need 1 double, so we convert it from one type to another
double_struct = struct.pack("ff", echo_reply[icmp_header_index + 5], echo_reply[icmp_header_index + 6])
time_in_packet = struct.unpack("d", double_struct)[0]

delta = timeReceived - time_in_packet

timeLeft = timeLeft - howLongInSelect
if timeLeft <= 0:
	return "Request timed out."
else:
	return delta
...

...
def isErrorInEcho(type, code):
    if type == 3:                       # means ICMP error
        if code == 0:
            print("Destination network unreachable")
        elif code == 1:
            print("Destination host unreachable")
        elif code == 2:
            print("Destination protocol unreachable")
        elif code == 3:
            print("Destination port unreachable")
        elif code == 6:
            print("Destination network unknown")
        elif code == 7:
            print("Destination host unknown")
        return True
    return False

...

pings_number = 10

min_rtt = 10
max_rtt = 0
total_rtt_sum = 0
rtt_number = 0
packets_lost = 0

# Send ping requests to a server separated by approximately one second
for i in range(pings_number) :
	delay = doOnePing(dest, timeout)
	print("RTT - " + str(delay) + "s")

	if isinstance(delay, str):
		packets_lost = packets_lost + 1
	else:
		if delay < min_rtt:
			min_rtt = delay
		elif delay > max_rtt:
			max_rtt = delay
		total_rtt_sum = total_rtt_sum + delay
		rtt_number = rtt_number + 1

	time.sleep(1)# one second

print("")
print("Max RTT - " + str(max_rtt) + "s")
print("Min RTT - " + str(min_rtt) + "s")
print("Average RTT - " + str(total_rtt_sum / rtt_number) + "s")
print("Packets lost - " + str(packets_lost / pings_number * 100) + "%")

...

static void notifyNeighboringNodes()
{
	// Send the distance vector to 1, 2, and 3 nodes:
	
	struct rtpkt updatePacket;
	updatePacket.sourceid = 0;
	for (int i = 0; i < 4; ++i)
	{
		updatePacket.mincost[i] = dt0.costs[i][0];
	}
	
	for (int i = 1; i < 4; ++i)
	{
		updatePacket.destid = i;
		tolayer2(updatePacket);
	}
}

void rtinit0() 
{
	// Initialize a distance vector:
	
	// destination 0:
	dt0.costs[0][0] = 0;
	dt0.costs[0][1] = 999;		// source 0 and dest 0 through 1/2/3 makes no sense, so assign "infinity"
	dt0.costs[0][2] = 999;
	dt0.costs[0][3] = 999;
	
	// destination 1:
	...
	
	// destination 2:
	...
	
	// destination 3:
	...
	
	// printf("Node 0 initialization at %f\n\n", clocktime);
	
	printdt0(&dt0);
	
	notifyNeighboringNodes();	// to spread the info about "this node"s distance values to its neighbors
}

void rtupdate0(rcvdpkt)
  struct rtpkt *rcvdpkt;
{
	int srcNode = rcvdpkt->sourceid;
	
	// iterate over min costs of another node:
	
	printf("\nBefore update:\n");
	printdt0(&dt0);

	
	bool wasUpdated = false;
	for (int i = 0; i < 4; ++i)
	{
		if (dt0.costs[i][0] > rcvdpkt->mincost[i] + dt0.costs[srcNode][0])
		{
			dt0.costs[i][0] = rcvdpkt->mincost[i] + dt0.costs[srcNode][0];
			wasUpdated = true;
		}
	}
	
	// printf("Node 0 update at %f\n\n", clocktime);
		
	if (wasUpdated)
	{
		printf("\nAfter update:\n");
		printdt0(&dt0);
		printf("\nCosts to other nodes: 1 - %d, 2 - %d, 3 - %d\n", dt0.costs[1][0], dt0.costs[2][0], dt0.costs[3][0]);
		notifyNeighboringNodes();
	}
}