正如Stefano和Ibanez所说，版本"存在问题.

As Stefano and Ibanez commented is a problem with "versions".

您正在使用的SignalR客户端能够连接到ASPNET Core，但不能连接到ASPNET服务器，就像提到的错误一样.

The client of SignalR you are using is able to connect to ASPNET Core but not ASPNET server like error mentioned.

如果您知道ASPNET Core是基于.Net Framework(CLR)的用于多平台的产品.

If you know ASPNET Core is a split from .Net Framework (CLR) based for multiplatform.

然后在这种情况下您有两个选择.

Then you have two options over this scenario.

首先，如果您希望继续使用ASPNET服务器端，则可以更改客户端.然后将您使用的库更改为支持ASPNET的库.看一下: SIGNALR-ASPNET与ASPNET Core

First you can change your client side if you desire to continue using ASPNET server side. Then change the library you using to one that supports ASPNET. Give a look: SIGNALR - ASPNET vs ASPNET Core

第二，例如，可以更改服务器端并将ASPNET Core for SignalR用作微服务.然后继续使用ASPNET Core SignalR库实现您的客户端.

Second you can change your server side and use ASPNET Core for SignalR, as a microservice, for example. Then continue implementing your client with ASPNET Core SignalR library.