Artificially create a connection timeout error

I've had a bug in our software that occurs when I receive a connection timeout. These errors are very rare (usually when my connection gets dropped by our internal network). How can I generate this kind of effect artificially so I can test our software?

If it matters the app is written in C++/MFC using CAsyncSocket classes.

Edit:

I've tried using a non-existent host, and I get the socket error:

WSAEINVAL (10022) Invalid argument

My next attempt was to use Alexander's suggestion of connecting to a different port, e.g. 81 (on my own server though). That worked great. Exactly the same as a dropped connection (60 second wait, then error). Thank you!

Solution 1:

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

Solution 2:

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.

Solution 3:

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)

Solution 4:

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

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

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

Solution 5:

The following URL always gives a timeout, and combines the best of @Alexander and @Emu's answers above:

http://example.com:81

Using example.com:81 is an improvement on Alexander's answer because example.com is reserved by the DNS standard, so it will always be unreachable, unlike google.com:81, which may change if Google feels like it. Also, because example.com is defined to be unreachable, you won't be flooding Google's servers.

I'd say it's an improvement over @emu's answer because it's a lot easier to remember.