A peer-to-peer network for file downloading. It resembles some features of Bittorrent, but much simplified. There are two pieces of software – peer and file owner.The file owner has a file, and it breaks the file into chunks of 100KB, each stored as a separate file. Note that the last chunk can be smaller than 100KB. The minimum number of chunks that the file can be split into is 5. The file owner listens on a TCP port. It is designed such that it can run multiple threads to serve multiple clients simultaneously.
Each peer should be able to connect to the file owner to download some chunks. It then has two threads of control, one acting as a server that uploads the local chunks to another peer (referred to as upload neighbor), and the other acting as a client that downloads chunks from a third peer (referred to as download neighbor). So each peer has two neighbors, one of which will get chunks from this peer and the other will send chunks to this peer. Neighboring relationship as given by the user in the congfiguration file as long as the network is connected.
The neighboring relationship may be encoded through input parameters (see below).
- Start the file owner process, giving a listening port.
- Start five peer processes, one at a time, giving the file owner’s listening port, the peer’s listening port, and its download neighbor’s (another peer) listening port.
- Each peer connects to the server’s listening port. The latter creates a new thread to upload one or several file chunks to the peer, while its main thread goes back to listening for new peers.
- After receiving chunk(s) from the file owner, the peer stores them as separate file(s) and creates a summary file, listing the IDs of the chunks it has.
- The peer then proceeds with two new threads, with one thread listening to its upload neighbor to which it will upload file chunks, and the other thread connecting to its download neighbor.
- The peer requests for the chunk ID list from the download neighbor, compares with its own to find the missing ones, and randomly requests a missing chunk from the neighbor. In the meantime, it sends its own chunk ID list to its upload neighbor, and upon request uploads chunks to the neighbor.
- After a peer has all file chunks, it combines them for a single file.
- A peer outputs its activity to its console whenever it receives a chunk, sends a chunk, receives a chunk ID list, sends out a chunk ID list, requests for chunks, or receives such a request.