Creating A Single Threaded Server with AnyEvent (Perl)

anyevent, perl, webserver

Solution

You're blocking inside a callback. That's not allowed. There are a few ways to handle this. My preference is to launch a Coro thread from within the tcp_server callback. But without Coro, something like this might be what you're looking for:

#!/usr/bin/env perl5.16.2

use AnyEvent;
use AnyEvent::Handle;
use AnyEvent::Socket;

my $cv = AE::cv;

my $host = '127.0.0.1';
my $port = 44244;

my %connections;
tcp_server(
           $host, $port, sub {
               my ($fh) = @_;

               print "Connected...\n";

               my $handle;
               $handle = AnyEvent::Handle->new(
                                               fh => $fh,
                                               poll => 'r',
                                               on_read => sub {
                                                   my ($self) = @_;
                                                   print "Received: " . $self->rbuf . "\n";
                                               },
                                               on_eof => sub {
                                                   my ($hdl) = @_;
                                                   $hdl->destroy();
                                               },
                                              );
               $connections{$handle} = $handle; # keep it alive.

               return;
           });

print "Listening on $host\n";

$cv->recv;

Note that I'm only waiting on one condvar. And I'm storing the handles to keep the AnyEvent::Handle objects alive longer. Work to clean up the $self->rbuf is left as an excersise for the reader :-)

Question cross-posted, answer, too :-)

Problem

I'm working on creating a local service to listen on localhost and provide a basic call and response type interface. What I'd like to start with is a baby server that you can connect to over telnet and echoes what it receives. I've heard AnyEvent is great for this, but the documentation for AnyEvent::Socket does not give a very good example how to do this. I'd like to build this with AnyEvent, AnyEvent::Socket and AnyEvent::Handle. Right now the little server code looks like this: ``` #!/usr/bin/env perl use AnyEvent; use AnyEvent::Handle; use AnyEvent::Socket; my $cv = AnyEvent->condvar; my $host = '127.0.0.1'; my $port = 44244; tcp_server($host, $port, sub { my($fh) = @_; my $cv = AnyEvent->condvar; my $handle; $handle = AnyEvent::Handle->new( fh => $fh, poll => "r", on_read => sub { my($self) = @_; print "Received: " . $self->rbuf . "\n"; $cv->send; } ); $cv->recv; }); print "Listening on $host\n"; $cv->wait; ``` This doesn't work and also if I telnet to localhost:44244 I get this: ``` EV: error in callback (ignoring): AnyEvent::CondVar: recursive blocking wait attempted at server.pl line 29. ``` I think if I understand how to make a small single threaded server that I can connect to over telnet and prints out whatever its given and then waits for more input, I could take it a lot further from there. Any ideas?

Original source