1. DMET 602: Networks and Media Lab
Amr El Mougy
Yasmeen Essam
Hana Medhat
Mariam Samy

2. Old Format Total of 8 experiments
Each week the lecture explains the theoretical concepts
A quiz is given at the end of each lecture
The following the experiment is conducted in the lab
Students answer oral questions and submit a report

3. New Format Week Lectures Tutorials 1 Socket Programming Fundamentals
(One Quiz) 2
One Client, One Server
Many Clients, One Server (multi-threading)
Many Clients, Many Servers
Project Evaluation 3 4 5
Web Applications Fundamentals
(Two Quizzes) 6
Basics of Web servers
HTTP Requests
Sessions
Security Certificates 7 8 9
Multicasting (Quiz) 10
QoS (Quiz)
Multicasting Experiment 11
Mobile IP (Quiz)
QoS Experiment 12
Mobile IP Experiment

4. Regulations: In the Lab
Cross-attendance is not allowed
If you have a critical reason that prevents you from attending the lab you have to inform your TA before your slot. If your excuse is accepted you will be assigned to a different slot.
If you don’t inform the TA before your slot, you get an F in the experiment and your attendance will not be counted
No compensation is offered to any student who will miss his lab for any reason (except a force majeure) and no switching between slots is allowed.
Arriving more than 15 mins late to a lab slot earns you an F and your attendance will not be counted
In case your lab time happens to be OFF for an official holiday, assume that you did the experiment and proceed with the rest of the schedule normally, you will be compensated at the end of the term

5. Grading Scheme Quizzes are best 5/6
In-lab Tasks/Oral Questions are divided evenly between the three course parts (11% for the tasks in socket programming, 11% for the tasks in web applications, 11% for all experiments combined)
Same division goes for the project evaluation/lab report

6. Networking Crash Course

7. Encapsulation destination source application transport network link
message M
application
transport
network
link
physical
segment Ht M Ht
datagram Ht Hn M Hn
frame Ht Hn Hl M
link
physical
switch
destination
network
link
physical Ht Hn M Ht Hn Hl M M
application
transport
network
link
physical Ht Hn M Ht M Ht Hn M
router Ht Hn Hl M
Introduction

8. Transport services and protocols
provide logical communication between app processes running on different hosts
transport protocols run in end systems
send side: breaks app messages into segments, passes to network layer
rcv side: reassembles segments into messages, passes to app layer
more than one transport protocol available to apps
Internet: TCP and UDP
application
transport
network
data link
physical
logical end-end transport
application
transport
network
data link
physical
Transport Layer

9. Internet transport-layer protocols
reliable, in-order delivery (TCP)
congestion control
flow control
connection setup
unreliable, unordered delivery: UDP
no-frills extension of “best- effort” IP
services not available:
delay guarantees
bandwidth guarantees
application
transport
network
data link
physical
network
data link
physical
network
data link
physical
logical end-end transport
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
application
transport
network
data link
physical

10. Developing an Internet App
Application programmer
Doesn’t need to send IP packets
Doesn’t need to send Ethernet frames
Doesn’t need to know how TCP implements reliability
Only need a way to pass the data down
Socket is the API to access transport layer functions

11. What the Lower Layer Needs
We pass the data down. What else does the lower layer need to know?
How to identify the destination process?
Where to send the data? (Addressing)
What process gets the data when it is there? (Multiplexing)

12. Sockets An interface between application and network
The application creates a socket
The socket type dictates the style of communication
reliable vs. best effort
connection-oriented vs. connectionless
Once configured the application can
pass data to the socket for network transmission
receive data from the socket (transmitted through the network by some other host)

13. Multiplexing/demultiplexing
Demultiplexing at rcv host:
Multiplexing at send host:
delivering received segments
to correct socket
gathering data from multiple
sockets, enveloping data with
header (later used for
demultiplexing)
= socket
= process
application
application
application P3 P1 P2 P4 P1
transport
transport
transport
network
network
network
link
link
link
physical
physical
physical
host 3
host 1
host 2
Transport Layer

14. Identifying the Destination
Addressing
IP address
hostname (resolve to IP address via DNS)
Multiplexing
port
Server socket address
:80
Client socket address
:3479
FTP Server
(port 21)
Client
HTTP Server
(port 80)
Connection socket pair
( :3479, :80)
Client host address
Server host address

15. Choosing Port Numbers UDP TCP
Source port:
26145
Dest. port: 80
Src IP: C
Dest. IP: B
UDP
TCP
Source port:
19157
Dest. port:
46428
Source port:
7532
Dest. port: 80
Src IP: C
Dest. IP: B
Source port:
46428
Dest. port:
19157
Source port:
26145
Dest. port: 80
Src IP: A
Dest. IP: B
Server is always listening on the well-known port number
Client chooses a source port number and inserts it in the header. The destination port number is the well- known port number
In the reply, the server inserts the port number received in the packet in the destination port number
Server is always listening on the well-known port number
Client chooses a source port number and inserts it in the header. The destination port number is the well-known port number
The server creates a socket for the client that is identifiable via the combination of src IP and src port address

16. Socket Programming
Goal: learn how to build client/server application that communicate using sockets
Socket API
introduced in BSD4.1 UNIX, 1981
explicitly created, used, released by apps
client/server paradigm
two types of transport service via socket API:
unreliable datagram
reliable, byte stream-oriented
a host-local,
application-created,
OS-controlled interface (a “door”) into which
application process can both send and
receive messages to/from another application process
socket

17. Socket Programming with TCP
Client must contact server
server process must first be running
server must have created socket (door) that welcomes client’s contact
Client contacts server by:
creating client-local TCP socket
specifying IP address, port number of server process
When client creates socket: client TCP establishes connection to server TCP
When contacted by client, server TCP creates new socket for server process to communicate with client
allows server to talk with multiple clients
source port numbers used to distinguish clients
application viewpoint
TCP provides reliable, in-order
transfer of bytes (“pipe”)
between client and server

18. Socket Programming with TCP
Example client-server app:
1) client reads line from standard input (inFromUser stream) , sends to server via socket (outToServer stream)
2) server reads line from socket
3) server converts line to uppercase, sends back to client
4) client reads, prints modified line from socket (inFromServer stream)
Client
process
client TCP socket

19. Client/Server Socket Interaction
Server (running on hostid)
Client
create socket,
port=x, for
incoming request:
welcomeSocket =
ServerSocket()
TCP
connection setup
close
connectionSocket
read reply from
clientSocket
create socket,
connect to hostid, port=x
clientSocket =
Socket()
wait for incoming
connection request
connectionSocket =
welcomeSocket.accept()
send request using
clientSocket
read request from
connectionSocket
write reply to

20. Example: Java Client import java.io.*; import java.net.*;
class TCPClient {
public static void main(String argv[]) throws Exception {
String sentence;
String modifiedSentence;
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("hostname", 6789);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());
Create
input stream
Create
client socket,
connect to server
Create
output stream
attached to socket

21. Example: Java Client (Cont’d)
Create
input stream
attached to socket
BufferedReader inFromServer =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
clientSocket.close(); }
Send line
to server
Read line
from server

22. Example: Java Server Create welcoming socket at port 6789
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception {
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));
Create
welcoming socket
at port 6789
Wait, on welcoming
socket for contact
by client
Create input
stream, attached
to socket

23. Example: Java Server (Cont’d)
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence); }
Create output
stream, attached
to socket
Read in line
from socket
Write out line
to socket
End of while loop,
loop back and wait for
another client connection

24. Project Description Chatting application using TCP socket programming
Multiple clients, two servers
Clients are associated with a particular server
Messages should be sent from any client to any client
The project should have a GUI that implements all required features

25. Client Functionalities
1. Join(name): The client uses this message to log on to the server (i.e., initiate a chat session).The client must send this message first, before sending any other messages. The member name is any name the client chooses to be identified by.
2. GetMemberList(): This message asks for a list of all members on the network.
3. Chat (Source, Destination, TTL, Message): The chat message that the user will send to another user.
Any chat message consists of three header fields and a body:
 - Source: The id of the sender.
- Destination: The id of the receiver.
- Time To Live (TTL): TTL is a counter which is decremented at each chat server, when it reaches zero the message should be discarded and an error message should be sent to the sender. The purpose of TTL is to prevent the message from looping infinitely in the network. The default value for the TTL is set to 2.
4. Quit: This message is used to log off.

26. Server Functionalities
1. JoinResponse: This is the response to the join request of the client whether accepted or not. (Note: the client is only rejected when he registers with a used name).
2. MemberListResponse: This sends the list of all members to the client upon request.
3. Route (Message, Destination): This method sends the message to the targeted destination. The server should check whether the destination is directly connected to it or not. In the case where the destination is directly connected to it, then it will directly forward the message. However if the destination is not found in the list of clients connected to the server, then it will send the message to the other chat server.