Requirements

1. In order to build a chat app, we will learn about using UDP sockets to broadcast online presence.
2. You will write a client program using socket(), setsockopt(), and sendto() to broadcast your presence to any servers on the CSLabs subnet. We will discuss how to use those socket API calls.
3. You will adapt the server program I showed in lecture to listen for presence messages.
4. In your assignment repo, please submit one Makefile which builds a client called client and a server called server
5. Your client should broadcast an online message to to the subnet, sleep for two seconds, then broadcast an offline message to the subnet.
6. Your server should print the presence messages it receives

Network Specs

1. The CSLabs subnet includes all of the vlabNN hosts and the g12NN hosts. Do not use the kudlickNN hosts as they are on a different network.
2. The UDP broadcast address for the CSLabs subnet is 10.10.13.255.
3. For our project, we will use port 8221 for online presence messages.

Sample Output

phpeterson@vlab01:lab07 $ ./server

phpeterson@vlab00:lab07 $ ./client phpeterson
online: phpeterson
offline: phpeterson

Now the server should output:

Presence: online: phpeterson on host host: vlab00.cs.usfca.edu
Presence: offline: phpeterson on host host: vlab00.cs.usfca.edu

Rubric

1. 70 pts: client broadcasts correctly
2. 20 pts: server listens correctly
3. 10 pts: neatness, including error handling