This is another version of
openFreePort function. This function has fewer dependencies than the
openFreePort returns a socket on a random port and the port it has been bound to.
openFreePort :: IO (Int, Socket)
wait will attempt to connect to a host and port until it is successful. Between each unsuccessful attempt, it sleeps for 10 ms.
Here is an example of the primary function:
import Network.Socket.Wait (wait) void $ forkIO $ Warp.run 7000 app -- Wait for the server to start listening on the socket wait "127.0.0.1" 7000 -- Communicate with the server ...
In bash one could write:
while ! nc -z localhost 7000 ; do sleep 0.01 ; done
The bash script above was copied from this stackoverflow answer https://stackoverflow.com/a/50008755
Changelog for wait-on-port
0.0.0.1 First version
0.2.0.0 Rework internals and change
EventHandlers m. Fix bug if host could not be found. It would loop forever and now throws.