diff options
Diffstat (limited to 'contrib/perl5/pod/perlipc.pod')
| -rw-r--r-- | contrib/perl5/pod/perlipc.pod | 58 |
1 files changed, 47 insertions, 11 deletions
diff --git a/contrib/perl5/pod/perlipc.pod b/contrib/perl5/pod/perlipc.pod index 8760257..a1df3e4 100644 --- a/contrib/perl5/pod/perlipc.pod +++ b/contrib/perl5/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 @@ -661,13 +660,14 @@ instead. BEGIN { $ENV{PATH} = '/usr/ucb:/bin' } use Socket; use Carp; - $EOL = "\015\012"; + my $EOL = "\015\012"; sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" } my $port = shift || 2345; my $proto = getprotobyname('tcp'); - $port = $1 if $port =~ /(\d+)/; # untaint port number + + ($port) = $port =~ /^(\d+)$/ or die "invalid port"; socket(Server, PF_INET, SOCK_STREAM, $proto) || die "socket: $!"; setsockopt(Server, SOL_SOCKET, SO_REUSEADDR, @@ -703,14 +703,15 @@ go back to service a new client. BEGIN { $ENV{PATH} = '/usr/ucb:/bin' } use Socket; use Carp; - $EOL = "\015\012"; + my $EOL = "\015\012"; sub spawn; # forward declaration sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" } my $port = shift || 2345; my $proto = getprotobyname('tcp'); - $port = $1 if $port =~ /(\d+)/; # untaint port number + + ($port) = $port =~ /^(\d+)$/ or die "invalid port"; socket(Server, PF_INET, SOCK_STREAM, $proto) || die "socket: $!"; setsockopt(Server, SOL_SOCKET, SO_REUSEADDR, @@ -744,6 +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: $!"; @@ -835,7 +837,7 @@ domain sockets can show up in the file system with an ls(1) listing. You can test for these with Perl's B<-S> file test: unless ( -S '/dev/log' ) { - die "something's wicked with the print system"; + die "something's wicked with the log system"; } Here's a sample Unix-domain client: @@ -863,6 +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'; @@ -899,6 +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 @@ -922,7 +948,7 @@ For those preferring a higher-level interface to socket programming, the IO::Socket module provides an object-oriented approach. IO::Socket is included as part of the standard Perl distribution as of the 5.004 release. If you're running an earlier version of Perl, just fetch -IO::Socket from CPAN, where you'll also find find modules providing easy +IO::Socket from CPAN, where you'll also find modules providing easy interfaces to the following systems: DNS, FTP, Ident (RFC 931), NIS and NISPlus, NNTP, Ping, POP3, SMTP, SNMP, SSLeay, Telnet, and Time--just to name a few. @@ -950,7 +976,7 @@ looks like this: Here are what those parameters to the C<new> constructor mean: -=over +=over 4 =item C<Proto> @@ -1022,7 +1048,7 @@ something to the server before fetching the server's response. } The web server handing the "http" service, which is assumed to be at -its standard port, number 80. If your the web server you're trying to +its standard port, number 80. If the web server you're trying to connect to is at a different port (like 1080 or 8080), you should specify as the named-parameter pair, C<< PeerPort => 8080 >>. The C<autoflush> method is used on the socket because otherwise the system would buffer @@ -1145,7 +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 @@ -1245,6 +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 @@ -1295,6 +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 |
