function opts( options ) {
	var out = {};
	if ( hasOwnProp( options, 'port' ) ) {
		out.port = options.port;
	}
	if ( hasOwnProp( options, 'maxport' ) ) {
		out.maxport = options.maxport;
	}
	if ( hasOwnProp( options, 'hostname' ) ) {
		out.hostname = options.hostname;
	}
	if ( hasOwnProp( options, 'address' ) ) {
		out.address = options.address;
	}
	return out;
}
Extracts HTTP server options from input function options.

@private
@param {Options} options - function options
@param {NonNegativeInteger} [options.port] - server port
@param {NonNegativeInteger} [options.maxport] - max server port
@param {string} [options.hostname] - server hostname
@param {string} [options.address] - server address
@returns {Options} server options

@example
var options = {
    'html': '<h1>beep</h1>',
    'open': true,
    'port': 7331,
    'address': '127.0.0.1'
};
var out = opts( options );
// returns {'port': 7331, 'address': '127.0.0.1'}