code: public void invoke(InputStream is, OutputStream os,
                         SerializerFactory serializerFactory)
          throws Exception
      {
          boolean isDebug = false;
  
          if (isDebugInvoke()) {
              isDebug = true;
  
              PrintWriter dbg = createDebugPrintWriter();
              HessianDebugInputStream dIs = new HessianDebugInputStream(is, dbg);
              dIs.startTop2();
              is = dIs;
              HessianDebugOutputStream dOs = new HessianDebugOutputStream(os, dbg);
              dOs.startTop2();
              os = dOs;
          }
  
          HessianInputFactory.HeaderType header = _inputFactory.readHeader(is);
  
          AbstractHessianInput in;
          AbstractHessianOutput out;
  
          switch (header) {
              case CALL_1_REPLY_1:
                  in = _hessianFactory.createHessianInput(is);
                  out = _hessianFactory.createHessianOutput(os);
                  break;
  
              case CALL_1_REPLY_2:
                  in = _hessianFactory.createHessianInput(is);
                  out = _hessianFactory.createHessian2Output(os);
                  break;
  
              case HESSIAN_2:
                  in = _hessianFactory.createHessian2Input(is);
                  in.readCall();
                  out = _hessianFactory.createHessian2Output(os);
                  break;
  
              default:
                  throw new IllegalStateException(header + " is an unknown Hessian call");
          }
  
          if (serializerFactory != null) {
              in.setSerializerFactory(serializerFactory);
              out.setSerializerFactory(serializerFactory);
          }
  
          try {
              invoke(_service, in, out);
          } finally {
              in.close();
              out.close();
  
              if (isDebug)
                  os.close();
          }
      }
docs: Invoke the object with the request from the input stream.
  
  @param in the Hessian input stream
  @param out the Hessian output stream