Q: Why does the whole program crash when the remote client closes its socket before the server is done? A: Because SIGPIPE is not blocked. Use UnixSignals.setHandler.

maybebug.cm

Group is
        $cml/basis.cm
        $cml/cml.cm
        $cml-lib/smlnj-lib.cm
        maybebug.sml

maybebug.sml

(* ml-build maybebug.cm && sml @SMLload=maybebug *)
(* then in another terminal, nc localhost 8989 and interrupt it before it gets to zero *)
structure Test = struct

open TextIO
structure SU = SockUtil

exception Foo of string

fun connMain s =
    let fun ds str = (print "in\n";
                      SU.sendStr (s, str);
                      print "out\n")

        fun count 0 = ds ("Bye!\r\n")
          | count n = (ds ("Hello " ^ (Int.toString n) ^ "\r\n");
                       CML.sync (CML.timeOutEvt (Time.fromReal 0.5));
                       count (n - 1))
    in
        count 5;
        raise Foo "Eek";
        print "Closing the connection.\n";
        Socket.close s
    end

fun catchWrap f arg =
 fn () =>
    f arg
    handle v => print ("Oh no: " ^ (General.exnMessage v) ^ "\n")

fun acceptLoop server_sock =
    let val (s, _) = Socket.accept server_sock
    in
        print "Accepted a connection.\n";
        CML.spawn (catchWrap connMain s);
        acceptLoop server_sock
    end

fun cml_main (program_name, arglist) =
    let val s = INetSock.TCP.socket()
    in
        Socket.Ctl.setREUSEADDR (s, true);
        Socket.bind(s, INetSock.any 8989);
        Socket.listen(s, 5);
        print "Entering accept loop...\n";
        acceptLoop s
    end

fun main (program_name, arglist) =
    (RunCML.doit (fn () => cml_main(program_name, arglist), NONE);
     OS.Process.success)

end