}
@Override
public ExtendedHandshakeChecker handshakeChecker(final URI uri, final Map<String, List<String>> requestHeaders) {
final String sentKey = requestHeaders.containsKey(Headers.SEC_WEB_SOCKET_KEY_STRING) ? requestHeaders.get(Headers.SEC_WEB_SOCKET_KEY_STRING).get(0) : null;
return new ExtendedHandshakeChecker() {
@Override
public void checkHandshakeExtended(Map<String, List<String>> headers) throws IOException {
try {
if (negotiation != null) {