podlators 1.06 released

[p5sagit/p5-mst-13.2.git] / pod / perlipc.pod

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 1894375..a1df3e4 100644 (file)
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -234,8 +234,7 @@ prepared to clean up core dumps now and again.
 
 To forbid signal handlers altogether would bars you from
 many interesting programs, including virtually everything in this manpage,
-since you could no longer even write SIGCHLD handlers.  Their dodginess
-is expected to be addresses in the 5.005 release.
+since you could no longer even write SIGCHLD handlers.  
 
 
 =head1 Using open() for IPC
@@ -661,14 +660,14 @@ instead.
     BEGIN { $ENV{PATH} = '/usr/ucb:/bin' }
     use Socket;
     use Carp;
-    $EOL = "\015\012";
+    my $EOL = "\015\012";
 
     sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" }
 
     my $port = shift || 2345;
     my $proto = getprotobyname('tcp');
 
-    ($port) = $port =~ /^(\d+)$/                        || die "invalid port";
+    ($port) = $port =~ /^(\d+)$/                        or die "invalid port";
 
     socket(Server, PF_INET, SOCK_STREAM, $proto)       || die "socket: $!";
     setsockopt(Server, SOL_SOCKET, SO_REUSEADDR,
@@ -704,7 +703,7 @@ go back to service a new client.
     BEGIN { $ENV{PATH} = '/usr/ucb:/bin' }
     use Socket;
     use Carp;
-    $EOL = "\015\012";
+    my $EOL = "\015\012";
 
     sub spawn;  # forward declaration
     sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" }
@@ -712,7 +711,7 @@ go back to service a new client.
     my $port = shift || 2345;
     my $proto = getprotobyname('tcp');
 
-    ($port) = $port =~ /^(\d+)$/                        || die "invalid port";
+    ($port) = $port =~ /^(\d+)$/                        or die "invalid port";
 
     socket(Server, PF_INET, SOCK_STREAM, $proto)       || die "socket: $!";
     setsockopt(Server, SOL_SOCKET, SO_REUSEADDR,
@@ -746,6 +745,7 @@ go back to service a new client.
                at port $port";
 
        spawn sub {
+           $|=1;
            print "Hello there, $name, it's now ", scalar localtime, $EOL;
            exec '/usr/games/fortune'           # XXX: `wrong' line terminators
                or confess "can't exec fortune: $!";
@@ -865,6 +865,7 @@ to be on the localhost, and thus everything works right.
     use Carp;
 
     BEGIN { $ENV{PATH} = '/usr/ucb:/bin' }
+    sub spawn;  # forward declaration
     sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" }
 
     my $NAME = '/tmp/catsock';
@@ -901,6 +902,29 @@ to be on the localhost, and thus everything works right.
        };
     }
 
+    sub spawn {
+       my $coderef = shift;
+
+       unless (@_ == 0 && $coderef && ref($coderef) eq 'CODE') {
+           confess "usage: spawn CODEREF";
+       }
+
+       my $pid;
+       if (!defined($pid = fork)) {
+           logmsg "cannot fork: $!";
+           return;
+       } elsif ($pid) {
+           logmsg "begat $pid";
+           return; # I'm the parent
+       }
+       # else I'm the child -- go spawn
+
+       open(STDIN,  "<&Client")   || die "can't dup client to stdin";
+       open(STDOUT, ">&Client")   || die "can't dup client to stdout";
+       ## open(STDERR, ">&STDOUT") || die "can't dup stdout to stderr";
+       exit &$coderef();
+    }
+
 As you see, it's remarkably similar to the Internet domain TCP server, so
 much so, in fact, that we've omitted several duplicate functions--spawn(),
 logmsg(), ctime(), and REAPER()--which are exactly the same as in the
@@ -952,7 +976,7 @@ looks like this:
 
 Here are what those parameters to the C<new> constructor mean:
 
-=over
+=over 4
 
 =item C<Proto>
 
@@ -1147,7 +1171,7 @@ does nothing but listen on a particular port for incoming connections.
 It does this by calling the C<< IO::Socket::INET->new() >> method with
 slightly different arguments than the client did.
 
-=over
+=over 4
 
 =item Proto
 
@@ -1247,6 +1271,11 @@ find yourself overly concerned about reliability and start building checks
 into your message system, then you probably should use just TCP to start
 with.
 
+Note that UDP datagrams are I<not> a bytestream and should not be treated
+as such. This makes using I/O mechanisms with internal buffering
+like stdio (i.e. print() and friends) especially cumbersome. Use syswrite(),
+or better send(), like in the example below.
+
 Here's a UDP program similar to the sample Internet TCP client given
 earlier.  However, instead of checking one host at a time, the UDP version
 will check many of them asynchronously by simulating a multicast and then
@@ -1297,6 +1326,11 @@ with TCP, you'd have to use a different socket handle for each host.
        $count--;
     }
 
+Note that this example does not include any retries and may consequently
+fail to contact a reachable host. The most prominent reason for this
+is congestion of the queues on the sending host if the number of
+list of hosts to contact is sufficiently large.
+
 =head1 SysV IPC
 
 While System V IPC isn't so widely used as sockets, it still has some