====================================================================================================
  KVP demo project
====================================================================================================

This project contains 2 applications, a server and a client app
to demonstrate client-sever communication using GNU libc.
Server has a KVP (key-value pair) database which can be
queried or updated by the clients.

The following tools were used:

 GNU Make 4.1
 gcc 7.3.0 (on ubuntu)
 glibc 2.27

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  How to compile the project
----------------------------------------------------------------------------------------------------

  server : [clean|all|build|rebuild] make app=server [strict=yes]

            if the server is compiled with the 'strict=yes' parameter,
            it won't allow clients to overwrite the values of existing keys.


  client : [clean|all|build|rebuild] make app=client

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  How to use the application
----------------------------------------------------------------------------------------------------

  server : ./kpv_server [-p portnum] [-f filename]

            cmdline args are optional, if they are not provided, default
            values will be used.
            ports can be used from [1024..65535] range
              
            default port: 5555
            default file: capitals.txt (contains countries with their capitals as key-value pairs)

            the server handles 3 different commands:

              'GET key'       - returns the associated value of the key
              'PUT key value' - saves a new KVP, or overwrites an existing
                                key's value (see 'strict=yes' macro)
              'bye'           - disconnects the client

            restrictions & information:
            --------------------------
            - commands (GET, PUT, bye) are not case sensitive, but each request must start with
              the command.
            - keys are case sensitive
            - new KVPs are stored only in RAM, all information is lost after server shutdown
            - key and value lengths are restricted to 16 and 32 characters
            - keys can contain only letters and digits, values can contain any character
            - at startup the registry file is loaded into RAM; in case of any problem, the
              server terminates with an error message.

            example:
            -------
            ./kvp_server -p6667

                * KVP Registry has been loaded
                * Server is started and listening on port 6667
                * Client connected from host 127.0.0.1:35090
                * Client disconnected from host 127.0.0.1:35090


  client :  ./kvp_client -a hostname -p portnum [-m] [-c "command"]
    
            -a address - eg: -a localhost
            -p portnum - eg: -p 5555 (ports can be used from [1024..65535] range)
            -m         - MANUAL mode (user can send commands to the server
                                      from the standard input like from telnet)
            -c "cmd"   - SINGLE mode (client executes the given command
                                      reads the response and terminates)

            client can run either in MANUAL or SINGLE mode. The default is MANUAL.

            example:
            -------
            ./kvp_client -alocalhost -p6667 -c "GET Hungary"

                SERVER: [Hungary] => [Budapest]