Differentiate Exceptions - Handling Timeouts and Errors

[JamesBewley]

I'm not familiar with the async style of C++ used in this library and must admit I am struggling a bit.

I have a working REST client application but I need to better handle unsuccessful requests such as timeouts. I need to be able to differentiate between errors so I can make an appropriate action (backoff / retry timeout or raise alarm for other errors).

Are all exceptions just std::exception with a message string set?
What is the best way to differentiate exceptions?

I found some code in the tests but it seems a bit fragile:

msg.find("The operation timed out") != std::string::npos | msg.find("The operation was timed out") != std::string::npos