Jon Fairbairn wrote:

I just got myself a copy of ghc-6.2.1 and was idly experimenting with Network in ghci.

Unfortunately a second attempt is not so happy:

Prelude System.Posix Network> do r <- recvFrom "localhost"$ PortNumber 9090; putStr r *** Exception: bind: resource busy (Address already in use)

According to the documentation there's some mention of "Address already in use" on this mailing list, but I couldn't find it -- I thought there used to be searchable archives of the mailing lists, but I couldn't find those either and resorted to google.

A little experimentation revealed that:

do sock <- listenOn$PortNumber 7607; (hdl,host,port)<- accept sock; s<-IO.hGetContents hdl; putStr$s; IO.hClose hdl; Network.Socket.sClose sock

is nicely repeatable. The following questions arise:

* Shouldn't recvFrom call sClose itself?

recvFrom can't close the socket until the data has been consumed.

* If not, how should one clean up after using recvFrom?

You can't; once recvFrom returns, there's no way to get at the listening socket (or, for that matter, the connection socket).

* Shouldn't sClose be reexported from Network?

Once you start down that route, you end up at the inevitable conclusion that everything from the raw syscall imports upwards needs to be re-exported.

* is there a general way to get ghci out of a state where it's got stuff open on inaccessible sockets?

The solution to most problems with the Network module is not to use the Network module, but to use Network.Socket instead. -- Glynn Clements