code: protected boolean doValidate(HttpRequestMessage request, final boolean isPostMethodAllowed) {
  
          if ( !isPostMethodAllowed ) {
              if ( request.getMethod() != HttpMethod.GET) {
                  return false;
              }
          } else {
              if ( request.getMethod() != HttpMethod.GET || request.getMethod() == HttpMethod.POST ) {
                  return false;
              }
          }
  
          if ( request.getVersion() != HttpVersion.HTTP_1_1) {
              return false;
          }
  
          if ( request.getRequestURI() == null ) {
              return false;
          }
  
          boolean ok = requireHeader(request, "Connection", "Upgrade");
          if ( !ok ) { return false; }
  
          ok = requireHeader(request, "Upgrade", "WebSocket");
          if ( !ok ) { return false; }
  
          ok = requireHeader(request, "Host");
  
          return ok;
      }
docs: Does the provided request form a valid web socket handshake request?
  
  @param request the candidate web socket handshake request
  @return true iff the provided request is a web socket handshake request.