Finding bugs in buggy client / server program. concurrent client transactions can update the server state

Included is a buggy client / server program. The server maintains a set of integer-valued slots that the clients can read and write. The objective of the server is to allow many concurrent clients to simultaneously query and update the slots. It provides no consistency guarantees between commands (e.g. 'SET a 5' then 'GET a' might return a non-5 value if another client SET it in between), but the state should always be equivalent to running the commands sequentially in some order. Slots names are case sensitive and values are 32 bit integers. Commands are case-insensitive.

Start server:

java -jar server.jar <name>

Example: java -jar server.jar test

Client has two modes, interactive and non-interactive:

java -jar client.jar <name> [optional command] [optional command] [...]

Example (interactive): java -jar client.jar test Example (non-interactive): java -jar client.jar test "create a" "set a 5" "get a"

Notes:

Server drops log in current directory under .log. Log is also echoed to standard out.

Communication is via a simple TCP protocol (you can use telnet in place of client for investigative purposes).

Commands:

CREATE <slot>      - create slot with given name and value 0
DROP <slot>        - remove slot with given name
LIST               - list slot names in any order
GET <slot>         - return value of slot
SET <slot> <value> - set value of slot
INCREMENT <slot>   - slot = slot + 1
SHUTDOWN           - disconnect client, stop server, write state
EXIT               - disconnect client

Link to the client/server programs