


=encoding UTF-8

=head1 NAME

JSON::Server - JSON-only server

=head1 SYNOPSIS

    
    use JSON::Server;
    my $js = JSON::Server->new (handler => \& hello, port => '7777', data => 'OK');
    $js->serve ();
    
    sub hello
    {
        my ($data, $input) = @_;
        return {%$input, hello => 'world', data => $data};
    }
    

(This example is included as L<F<synopsis.pl>|https://fastapi.metacpan.org/source/BKB/JSON-Server-0.00_05/examples/synopsis.pl> in the distribution.)


Then test your server:

    $ perl examples/synopsis.pl &
    $ telnet localhost 7777
    Trying 127.0.0.1...
    Connected to localhost.
    Escape character is '^]'.
    {"I'm feeling lucky":"punk"}
    {
            "I'm feeling lucky":"punk",
            "data":"OK",
            "hello":"world"
    }
    Connection closed by foreign host.


=head1 VERSION

This documents version 0.00_05 of JSON-Server
corresponding to L<git commit 71cae7de6b2d061388b6bcc05c5ef6efd2a280c1|https://github.com/benkasminbullock/json-server/commit/71cae7de6b2d061388b6bcc05c5ef6efd2a280c1> released on Sun Feb 7 08:01:36 2021 +0900.

=head1 DESCRIPTION

This sets up an internet socket through which JSON passes.

=head1 METHODS

=head2 new

    my $js = JSON::Server->new (handler => \& something, data => $my_data,
		                port => '3737');

=over

=item data

Your data which you want to pass to the handler. This can be omitted,
in which case the handler will be sent an undefined value as its first
argument.

=item handler

Your handler (callback).

    sub handler
    {
        my ($data, $input) = @_;
        return {error => "I don't like this input"};
    }
    my $js = JSON::Server->new (handler => \&handler);

The handler function should accept two arguments, the first is the
user data which is supplied to L</new> and the second is the parsed
input from the socket. It should return one value which is then passed
back through the socket as JSON. The user handler function does not
serialize or deserialize anything, usually it would take a hash
reference as an argument and return a hash reference as result.

If you do not supply a handler, the server substitutes an echo
function which merely returns your input back to you, and prints a
warning.

=item port

The port to serve on. This needs to be specified, there is no default
value.

=back

=head2 serve

    $js->serve ();

Serves JSON on the specified port. Input is JSON, output is
JSON. Non-JSON input results in a response of the form
C<{"error":"invalid JSON"}> being returned. What is or is not valid
JSON is decided by L<JSON::Parse/valid_json>.

=head1 CONTROLLING THE SERVER

There is a "backdoor" for controlling the server. To access this, you
need to send an object (a hash reference) with the key
C<JSON::Server::control>,

    send_to_server ({'JSON::Server::control' => 'stop'});

It accepts the following commands:

=over

=item stop

C<{"JSON::Server::control":"stop"}> causes the server to return from
its event loop. It prints a response
C<{"JSON::Server::response":"stopping"}> to acknowledge the control
message.

=back

Whatever else is sent in the object with the control message is
discarded.

=head1 DEPENDENCIES

=over

=item L<boolean>

C<boolean> is used as the compatibility module for putting C<true> or
C<false> values into the JSON, so if you need those in your output, 

    use boolean;

and then

    my $value = true;

etc. in your code to get C<true> and C<false> literals in your
JSON. (Perl's built-in C<undef> will produce C<null>. See the
documentation of L<JSON::Create> for full details about literals.)

=item L<IO::Socket>

This is used to communicate the information to and from the client.

=item L<JSON::Create>

This is used to encode the response JSON from a native structure.

=item L<JSON::Parse>

This is used to decode the received JSON into a native structure.

=item L<Unicode::UTF8/decode_utf8>

This is used to convert the received JSON from the socket before it is
passed to L</JSON::Parse>.

=back

=head1 SEE ALSO

=over

=item L<JRPC>

=item L<JSON::RPC::Dispatcher>

=item L<JSON::RPC>

=item L<RPC::JSON>

=back



=head1 AUTHOR

Ben Bullock, <bkb@cpan.org>

=head1 COPYRIGHT & LICENCE

This package and associated files are copyright (C) 
2021
Ben Bullock.

You can use, copy, modify and redistribute this package and associated
files under the Perl Artistic Licence or the GNU General Public
Licence.



