Artificially create a connection timeout error

Plenty of good answers but the cleanest solution seems to be this service

https://httpstat.us/504?sleep=60000

You can configure the timeout duration (up to 230 seconds) and eventual return code.

Connect to a non-routable IP address, such as 10.255.255.1.

If you are on a unix machine, you can start a port listening using netcat:

nc -l 8099

Then, modify you service to call whatever it usually does to that port e.g. http://localhost:8099/some/sort/of/endpoint

Then, your service will open the connection and write data, but will never get a response, and so will give you a Read Time Out (rather than Connection Refused)

Connect to an existing host but to a port that is blocked by the firewall that simply drops TCP SYN packets. For example, www.google.com:81.