gnutls[1]: 收到未知类型的记录包 91

Question

我在我的网络服务器中使用 gnutls 库 (3.4.11) 进行握手和加密，
在客户握手期间。我看到下面的错误消息并且握手失败。

“Received record packet of unknown type 91”错误到底说明了什么

我试着看代码

inline static int check_recv_type(gnutls_session_t session, content_type_t recv_type)
{
    switch (recv_type) {
    case GNUTLS_CHANGE_CIPHER_SPEC:
    case GNUTLS_ALERT:
    case GNUTLS_HANDSHAKE:
    case GNUTLS_HEARTBEAT:
    case GNUTLS_APPLICATION_DATA:
        return 0;
    default:
        gnutls_assert();
        _gnutls_audit_log(session,
                  "Received record packet of unknown type %u\n",
                  (unsigned int) recv_type);
        return GNUTLS_E_UNEXPECTED_PACKET;
    }

}

它只是说 GNUTLS_E_UNEXPECTED_PACKET。