Network, sClose

[Jon Fairbairn]

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

I tried 


   Prelude System.Posix Network> do r <- recvFrom "localhost"$ PortNumber 9090; putStr r

in one ghci and 

   Prelude Network> do sendTo "localhost" (PortNumber 9090) "jellied eels\n"

in another and was pleased to see 

   jellied eels

pop out of the first. 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?

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

* Shouldn't sClose be reexported from Network?

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

  Jón

-- 
Jón Fairbairn                                 Jon.Fairbairn at cl.cam.ac.uk