This is an individual work done in Ecole Polytechnique, in the course INF557: From the Internet to the IoT. It implements an distributed application using algorithms and patterns of routing protocols which:
- locally discover and maintain a peer set by way of periodical signaling and externally triggered events
- create a consistent distributed database
This application is supposed to be able to interoperate on different machines (i.e. different IP addresses) on the same local link with the same protocol specifications.
Simply compile with javac *.java and launch java Main. The program creates
a broadcast socket on port 4242 in the local network and launches all the
handlers: HelloSender, HelloReceiver, SynReceiver, ListReceiver, DubugReceiver.
We update our database every 5 seconds.
When testing with other machines, don't forget to change the ID (myID) inside Info, whose data must correspond to the machine launching the program itself.
There are three kinds of message: HelloMessage, SynMessage and ListMessage. The formats are specified in the corresponding source files. HelloSender broadcasts HelloMessage periodically, while HelloReceiver identifies those sent by others and updates the PeerTable, situated inside the class Info (my database). Even if the peer already exists in PeerTable, it verifies if the peer is well synchronized by checking its sequence number (version number).
Note that every peer has an expiration time and will be deleted from the database. According to situations, every identified peer has a corresponding peerState, as illustrated by stateMachine.png.
SynMessages are sent by HelloReceiver to a peer whenever it detects its peerState becomes HEARD/INCONSISTENT, and it keeps sending the same SYN until the peer's sequence number (version number) is incremented. These messages are meant to request new database from the others. SynReceiver is thus implemented to generate ListMessages to transfer my database. For this purpose, my database is split into pieces of length shorter than 255 bytes and included into multiple ListMessages.
ListReceiver has to assemble all received LIST and check if all messages are well received. Once all parts are assembled, it increments the peer's sequece number, updates its database in PeerTable. The process of synchronization with this peer is thus finished and the peer's peerState becomes SYNCHRONIZED.