1. TA: Donghyun (David) Kim
Homework 1 Review
TA: Donghyun (David) Kim

2. Overall Architecture
Hybrid Peer-to-Peer System
Server
Client1
Client2

3. Server Description Server responsibility
Maintain the list of online-clients
Server IP (IP-S) and Port Number (PORT-S) is known
Get IP-S in running time
Get PORT-S from input arguments
Prepare a data structure to maintain a list of client information
Client ID (ID-C), Client IP (IP-C), and Client Port Number (PORT-C)

4. Server Description – cont’
(IP-S, PORT-S)
Server
ID-C
IP-C
PORT-C 1
6000 2
UDP

5. Server Description – cont’
Waiting for messages from clients via UDP
JOIN, ID-C, IP-C, PORT-C
LEAVE, ID
Assume no two messages arrives at the same time
When membership is changed, send the updated list to the all of online-clients via UDP
In practice, only change can be sent
i.e. forward Join/leave message from a client to the other clients

6. Server Description – cont’
(IP-S, PORT-S)
Server
ID-C
IP-C
PORT-C 1
6000 2
UDP
JOIN/LEAVE
UPDATE on-line client list of

7. Client Architecture It is a peer (Client + Server)
Four user input arguments
Client ID (ID-C), Port number of the client (PORT-C)
ID-S, PORT-S
Learn its own IP (IP-C)
Two global variables
Thread1 and Thread2 should share one Boolean flag which define their actions
MODE: 1 or 2
A socket descriptor for the user to communicate with another client
SOCKET: -1 (disconnected) or other value
Assume no racing condition

8. Client Architecture – cont’
3 major threads (running at the same time)
Thread1
Mode1: Handling user input and connecting to another client via TCP
Mode2: Handling user input when connected
Thread2
Mode1: Listening a connection request from another via TCP
Mode2: Still, listening a connection request from another via TCP, but reject all other requests.
Thread3
Send a JOIN message to the with (ID-C, IP-C, PORT-C)
Listening a membership update from the server via UDP

9. Client Architecture – cont’
Thread1
Mode1: Handling user input and connecting to another client via TCP
DISPLAY-LIST: display the up-to-date list of online-clients
After a session is established, the connection can be terminated by typing “BYE” on any client
CONNECT ID-C: try establishing a connect to the client with ID-C
TERMINATE: terminate this client
Mode2: Handling user input when connected
Client
Thread1
Thread2
Thread3

10. Example
Server
ID-C
IP-C
PORT-C
(IP-S, PORT-S)
UDP

11. Example Server Client1 ID-C IP-C PORT-C (IP-S, PORT-S) UDP
MODE: 1, SD: -1
Client1
JOIN (ID-C1, IP-C1, PORT-C1)
Thread1
Thread2
TCP
Thread3
UDP

12. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
(IP-S, PORT-S
ID-C2, IP-C2, PORT-C2)
MODE: 1, SD: -1
MODE: 1, SD: -1
Client1
Client2
LIST{(ID-C1, IP-C1, PORT-C1)}
Thread1
Thread1
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

13. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
(IP-S, PORT-S
ID-C2, IP-C2, PORT-C2)
MODE: 1, SD: -1
MODE: 1, SD: -1
Client1
Client2
JOIN (ID-C2, IP-C2, PORT-C2)
Thread1
Thread1
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

14. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
LIST {(ID-C1, IP-C1, PORT-C1), (ID-C2, IP-C2, PORT-C2)}
MODE: 1, SD: -1
MODE: 1, SD: -1
Client1
Client2
Thread1
Thread1
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

15. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
MODE: 1, SD: -1
MODE: 2, SD: 5
Client1
Client2
Thread1
CONNECT REQ(ID-C2)
Thread1
TCP
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

16. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
MODE: 2, SD: 3
MODE: 2, SD: 5
Client1
Client2
Thread1
Thread1
TCP
TCP
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

17. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
MODE: 2, SD: 3
MODE: 2, SD: 5
Client1
Client2
BYE
Thread1
Thread1
TCP
TCP
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

18. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
MODE: 1, SD: -1
MODE: 1, SD: -1
Client1
Client2
Thread1
Thread1
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

19. Example Server Client1 Client2 ID-C IP-C PORT-C ID-C1 IP-C1 PORT-C1
(IP-S, PORT-S)
UDP
MODE: 1, SD: -1
MODE: 1, SD: -1
LEAVE (ID-C1)
Client1
Client2
Thread1
Thread1
Thread2
Thread2
TCP
TCP
Thread3
Thread3
UDP
UDP

20. Example Server Client2 ID-C IP-C PORT-C ID-C2 IP-C2 PORT-C2
(IP-S, PORT-S)
UDP
LIST {(ID-C2, IP-C2, PORT-C2)}
MODE: 1, SD: -1
Client2
Thread1
Thread2
TCP
Thread3
UDP