Tutorial 04 ZHANG Yuming

zy219@ie.cuhk.edu.hk

Week 04

Overview

This tutorial give hint of the coding for Project 01.

Project 01 In Project 01, you need to implement NetProbe. More specifically, you need to implement the following functions:

• Host mode

• Receive function for TCP (stream socket)

• Send function for TCP

• Receive function for UDP (Datagram socket)

• Send function for UDP

Sample code is provided at references:

• TCP: https://www.binarytides.com/winsock-socket-programming-tutorial/

• UDP: https://www.binarytides.com/programming-udp-sockets-c-linux/

Input parameters You need to get the following statistics

• stat

• pktsize

• pktrate

• pktnum

• sbufsize: sender buffer size

• rbufsize: receiver buffer size

• lhost: reciever’s local host (hostname or IP)

• lport: reciever’s listen port number

• rhost: sender’s remote host

• rport: sender’s remote port number

• proto: TCP/UDP

Input parameters Set buffer size (sbufsize, rbufsize)

• Call setsockopt (refer p.69)

Server parameter: (lhost, lport)

• Used for server (receiver) bind address

Client parameter: (rhost, rport)

• Used for client (sender) connect

Input parameters (stat)

• Display time, of the statistics

pktnum

• Number of message in application layer (NOT number of packet!!!!)

• For UDP: Number of message = Number of packet

• For TCP: A message is split into multiple packet.

pktsize

• Which is also the message size (Not the packet size!!!)

• For UDP: Number of message = Number of packet

• For TCP: A message is split into multiple packet.

• Do not mix these two.

Output statistics You need to get the following statistics

• Elapsed: which is “-stat’, the rest is during “-stat” ms

• Pkts: number of packet send/recv

• Lost: number/ratio of packet loss, note that only UDP receiver side need “Lost”

• Rate: Throughput

• Jitter: Inter packet arrival time variation

TCP (stream) Receive function

Here I will use TCP receive as an example to tell you how to calculate the statistics

Sample code:

TCP (stream) Receive function

Got time in milliseconds:

• My method is use clock_t in “time.h”

Sample code:

clock_t current_clock, previous_clock = clock();

while (true) {

double time_cost = (double)(current_clock - previous_clock) / CLOCKS_PER_SEC;

cum_time_cost = cum_time_cost + time_cost;

if (cum_time_cost > “-stat”){

// print your statistic messages

}

}

TCP (stream) Receive function Record the statistic:

• Use variable to record the number of packet, and the total received size

Sample code:

double cum_time_cost = 0, cum_bytes_recv = 0, total_time_cost = 0;

int recv_size, cum_packet_number = 0, cum_receive_size = 0, total_packet_number = 0;

while(…){

int recv_size = recv(sockfd_serve_client, peer_data, fetch_size, 0);

cum_receive_size = cum_receive_size + recv_size;

cum_packet_number++;

}

TCP (stream) Receive function Print statistics:

Sample code:

double throughput = (cum_bytes_recv * 8) / (cum_time_cost * 1000000);

printf("Receiver: [Elapsed] %.2f ms, [Pkts] %d, [Rate] %.2f Mbps\n", cum_time_cost * 1000, cum_packet_number,

throughput);