Solution for the SignalR error “Failed to start the connection. Error- Method Not Allowed” : .Net Core Errors Part III

You can find all .Net core posts here.

.Net Core was introduced in last few months and people has started adopting it.

In this series of post, I will put some frequent errors during .Net Core development and some important topics for the Core.

In this post we will see how to resolve the error:

Failed to start the connection. Error: Method Not Allowed

When this error occurs?

• When you upgrade your existing SignalR server project to .Net Core but do not upgrade the client
• When you create the SignalR server using .Net core but you use traditional .Net framework for the client

Why this error occurs?

• The error occurs because new SignalR does not allow you to use old server & new client or new server & old client
• It means if you create the SignalR server using .Net core then you must create the client using .Net Core

.Net team has stated about this as below:

What’s Changed?

We added a number of new features to SignalR for ASP.NET Core but we also decided to remove support for some of the existing features or change how they work. One of the consequences of this is that SignalR for ASP.NET Core is not compatible with previous versions of SignalR. This means that you cannot use the old server with the new clients or the old clients with the new server. (Ref – https://blogs.msdn.microsoft.com/webdev/2017/09/14/announcing-signalr-for-asp-net-core-2-0/)

How to resolve this error?

Resolution is simple.

If you decide to create SignalR server in .Net Core then you must create the clients in .Net core and vice versa.

Have a look here for my post on SignalR with .Net Core.

Hope it helps.