code: private boolean checkForH2MagicString(HttpInboundServiceContextImpl isc) {
  
          boolean hasMagicString = false;
          WsByteBuffer buffer;
  
          if (myTSC == null || myTSC.getReadInterface() == null ||
              (buffer = myTSC.getReadInterface().getBuffer()) == null) {
              return hasMagicString;
          }
  
          // read the buffer, flip it, and if there is a backing array pull that out
          buffer = buffer.duplicate();
          buffer.flip();
          byte[] bufferArray = null;
          if (buffer.hasArray()) {
              bufferArray = buffer.array();
          }
  
          // return true if the read buffer starts with the magic string
          if (bufferArray != null && bufferArray.length >= 24) {
              String bufferString = new String(bufferArray, 0, 24);
              if (bufferString.startsWith(HttpConstants.HTTP2PrefaceString)) {
                  hasMagicString = true;
              }
          }
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) {
              Tr.exit(tc, "checkForH2MagicString: returning " + hasMagicString);
          }
          buffer.release();
          return hasMagicString;
      }
docs: Check the beginning of the current read buffer for the http/2 preface string
  
  @param isc the HttpInboundServiceContextImpl to use
  @return true if the magic string was found