withSocketsDo

withSocketsDo :: IO a -> IO a
network Network.Socket Network.Socket.Internal, network-simple-tls Network.Simple.TCP.TLS
With older versions of the network library (version 2.6.0.2 or earlier) on Windows operating systems, the networking subsystem must be initialised using withSocketsDo before any networking operations can be used. eg. 
main = withSocketsDo $ do {...}
It is fine to nest calls to withSocketsDo, and to perform networking operations after withSocketsDo has returned. withSocketsDo is not necessary for the current network library. However, for compatibility with older versions on Windows, it is good practice to always call withSocketsDo (it's very cheap).
withSocketsDo :: () => IO a -> IO a
network-simple Network.Simple.TCP
With older versions of the network library (version 2.6.0.2 or earlier) on Windows operating systems, the networking subsystem must be initialised using withSocketsDo before any networking operations can be used. eg. 
main = withSocketsDo $ do {...}
It is fine to nest calls to withSocketsDo, and to perform networking operations after withSocketsDo has returned. withSocketsDo is not necessary for the current network library. However, for compatibility with older versions on Windows, it is good practice to always call withSocketsDo (it's very cheap).