Example of using Unicasts and Broadcasts

Question

I'm not too sure of what the difference between Unicasts and Broadcasts is. I could really use an example of their use that shows the difference between the two. Thank you!

Answer 1

Unicasting is sending a message to a specific computer, identified by its IP address. This is 99.9% of all normal internet traffic, be it TCP or UDP.

Examples are web surfing (HTTP), sending or receiving emails (SMTP, POP, IMAP), using Skype, filesharing (Bittorrent) orplaying games over the internet (everything from Mahjongg to Diablo III). Basically everything where exactly 2 computers communicate with each other. Often, one is considered a server and another being a client, but that's not strictly necessary (cf. peer-to-peer networking).

Broadcasting sends a packet to every computer in the local subnet, by addressing it to the "broadcast address", which is derived from the subnet IP range.

E.g. For a 192.168.0.0/24 network, the broadcast address would be 192.168.0.255.

You can only reach computers within your own subnet via broadcasting. It won't be routed out into other networks. Typical usecases are data exchange or advertising of services (such as game or media servers) between local computers.

The message will (barring network problems) reach all computers in the subnet, but not all of them need to handle the message, if they are not interested in it (e.g. a computer not running a game client won't be interested in a game servers' broadcasts).