Network.Socket endian problem?

Rich Neswold rich.neswold at
Wed Dec 13 13:29:18 EST 2006


I've written a program that uses UDP as its communication with other
processes. It was built with GHC 6.4.1 on MacOS 10.4 (PowerPC) and
works fine. When I moved the code to a Linux box (i386) and built it
with GHC 6.6, it didn't work. The problems turns out to be,
apparently, an endian problem. The socket is created with the
following snippet:

allocSocket :: IO Socket
allocSocket =
    do { s <- socket AF_INET Datagram 0
         ; handle (\e -> sClose s >> throwIO e) $
                       do { connect s (SockAddrInet 6802 0x7f000001)
                            ; return s

On the Macintosh, the socket only receives packets from, which is correct (and works). On the Linux machine,
the socket only accepts packets from The data
constructor SockAddrInet doesn't swap the bytes of the address
(although it correctly swaps the bytes of the port number!)

Changing the data constructor call to (SockAddrInet 6802 0x0100007f)
makes it work on Linux, but not on MacOS 10.4. (You can see what the
socket is bound to, on Linux, with "netstat -aun".)

I don't have access to GHC 6.4.1 on a Linux box to determine whether
this is a regression in 6.6 or simply an overlooked detail. Should I
file a PR? Am I doing something wrong?


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