C implmentation of a simple Dropbox like system with client and server modules that synchronize files both-ways and enable sharing of directories. This was completed as a part of my second year coursework (Spring 2012) for an assignment.

Compile the source using the Makefile provided.

Server Usage: Execute dbserver. Client Usage: dbclient -h server_hostname -d directory_to_sync -u username

###Working:

• Server stores synchronized directories in a directory called "server_files". [Check assumption #3].

• When the server is first run, it sets up the connection and listens for an incoming client request.

• When a client connects to the server, it first sends the login message.

• The server parses the login message, adds the client information and check if the directory being requested by the client to be synchronized has been previously synchronized by any other client. If so, a flag for synchronization for this client is enabled.

• Once logged in, the server expects a sync_message and processes the request accordingly.

• If an incoming sync_message is originating for a client who has its sharing flag set to true, then for every file sent in a sync_message packet by this client the server first checks to see if the file is present in the directory being shared, if so its name, size and last modified time are populated in this client's file_info array to enable effective shared synchronization.

• Once the server is in a state to send an empty sync_message to a client as well; this is said to be "completion of a CYCLE". After completion of a cycle, the refresh flag for a particular client (who has completed the cycle on the server) is set to true. Once a new sync_message arrives from the client beyond this point, all files in this client's file_info array are checked and compared with the files present in the server's sharing file system to see if any of these files have been modified on the server (using the modification times). This is done so that any files which have been changed on the server (say, by editing it or by some other client changing it possibly due to sharing) gets updated throughout.

###Assumptions:

1. The directory given by the client is present in the current working directory from which dbclient is called.

2. The relative path to a file on the server or client never exceeds 255 in length. Eg: 'server_files/client_dir/somefile' < 255.

3. A server, if rebooted is assumed to take no notice of files already present in its sharing file system from previous executions; upon booting. Hence the folders are presumed to be empty.