1. CS470 Programming Assignment 1 Zilong Ye

2. A Chat Application Goal: learn socket programming and implement a chat application for exchanging messages between remote users; Peer 1 Peer 3 Peer 2 Socket enables this “Hello” “Hi back”

3. Start the program Name your program as “chat” Specify the port number that the process is running on The process works like a unix shell E.g.: C://course/cs470/./chat 4545 >>

4. help Show the command manual E.g.: C://course/cs470/./chat 4545 >> help >> myip display IP address connect connect to another peer send send messages to peers …………. exit exit the program >>

5. myip Show the IP of your laptop E.g.: >> myip >> The IP address is 192.168.21.21 >>

6. myport Show the port number that the process runs on E.g.: >> myport >> The program runs on port number 4545 >>

7. connect E.g.: >> connect 192.168.21.22 5454 >> The connection to peer 192.168.21.22 is successfully established; >> Peer 2 displays the connection news and update its list On peer 2, e.g.: >> The connection to peer 192.168.21.22 is successfully established; >>

8. list List all the connected peers E.g.: >> connect 192.168.0.2 5000 >> The connection to peer 2 is successfully established; >> list id: IP address Port No. 1: 192.168.21.21 4545 2: 192.168.21.22 5454 3: 192.168.21.23 5000 4: 192.168.21.24 5000 >> On peer 2, e.g.: >> list id: IP address Port No. 1: 192.168.21.21 4545 >>

9. send E.g.: >> list id: IP address Port No. 1: 192.168.21.20 4545 2: 192.168.21.21 5454 3: 192.168.21.23 5000 4: 192.168.21.24 5000 >> send 2 Hello

10. send Peer 2 receives the message and should display the message >> Message received from 192.168.21.21: “Hello” >> list id: IP address Port No. 1: 192.168.21.20 4545 >> send 1 Hi, back >> Peer 1 receives the reply and should display the message >> Message received from 192.168.21.22: “Hi, back” >>

11. terminate Terminate the connection E.g.: >> list id: IP address Port No. 1: 192.168.21.21 4545 2: 192.168.21.22 5454 3: 192.168.21.23 5000 4: 192.168.21.24 5000 >> terminate 2 >> list id: IP address Port No. 1: 192.168.21.21 4545 3: 192.168.21.23 5000 4: 192.168.21.24 5000

12. terminate Peer 2 displays the termination news and update its connection list >> list id: IP address Port No. 1: 192.168.21.21 4545 >> Peer 192.168.21.21 terminates the connection >> list id: IP address Port No. >>

13. exit Terminate all the connections and exit the program; The other peers should display the exit news and update their peer list; E.g.: C://course/cs470/./chat 4545 >> help ……. >> list ……. >> exit C://course/cs470/

14. Useful links Socket Programming: Beej Socket Guide: http://beej.us/guide/bgnet http://beej.us/guide/bgnet Select function: http://www.mkssoftware.com/docs/man3/sel ect.3.asp http://www.mkssoftware.com/docs/man3/sel ect.3.asp

15. How to recognize the command input

16. Code structure

17. Fill out addr_info structure

18. Regular steps for socket programming

19. How to use connect

20. myip 127.0.0.1 is your “Lo” IP address, and it is NOT what we want; Create a UDP socket to contact any public DNS server (e.g., 8.8.8.8 or 8.8.4.4 by Google) to get a response from the DNS server and obtain your real IP address

21. Select based I/O

22. Select() related functions

23. Select() example