SignalR is designed for real-time messaging using several protocols (WebSockets, Long Polling, Server Sent Events, or Forever Frame). On the other hand, Service Bus type protocols (Such as MSMQ, RabbitMQ, Azure Service Bus) are designed for decoupled communication. The use cases can overlap, but in general, if you're looking for real-time updates (chat, tickers, notifications of a user status change) then SignalR is a good solution. One key difference is that MSMQ and the like do not require that the recipients, or subscribers, be online at the time the message is sent, whereas a SignalR client must be listening or it will miss the notification.
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