Hi Monks, I'm trying to write a network server which has to handle many concurrent connections. If I write it using accept()/fork(), i quickly wind up with too many processes, none of which gets a chance to do anything useful. It is possible that perl is not the tool for this job, but I'm having a go using using IO::Epoll. I'm currently confused about getting notification that the socket has gone away - I register EPOLLHUP in my epoll_ctl, but when I close a client connection, I only receive the read event. I know that I need to use sysread instead of readline, but it's not causing me a problem at the minute. The server code is

#!/usr/bin/perl -w
use strict;
use IO::Socket;
use IO::Epoll;# qw(:compat);
use Data::Dumper;
my $server = IO::Socket::INET->new(LocalPort => 12345, Type => SOCK_ST
+REAM, Listen => 1) or die $!;
my $poll = epoll_create(10);
epoll_ctl($poll, EPOLL_CTL_ADD, fileno $server, EPOLLIN | EPOLLERR | E
+POLLHUP) >= 0
               || die "epoll_ctl: $!\n";
print "fd ".fileno($server)." EPOLLIN ".EPOLLIN." EPOLLERR ".EPOLLERR.
+" EPOLLHUP ".EPOLLHUP."\n";
my @client;
while(1){
        if(my $events = epoll_wait($poll, 10,1000)){
                print "epoll said: ".Data::Dumper->Dump([$events]);
                for my $e (@$events){
                        if ($e->[0] == fileno($server)){
                                #new connection
                                my $client = $server->accept();
                                $client[fileno($client)] = $client;
                                epoll_ctl($poll, EPOLL_CTL_ADD, fileno
+ $client, EPOLLIN | EPOLLERR |EPOLLHUP) >= 0
                                               || die "epoll_ctl clien
+t: $!\n";
                        }else{
                                #existing connection
                                if ($e->[1] & EPOLLIN){
                                        my $x = readline($client[$e->[
+0]]);
                                        print "client ".$e->[0]." said
+ '$x'\n";
                                        if (!defined($x)){
                                                close $client[$e->[0]]
+;
                                        }
                                }else{
                                        warn "polled\n";
                                        print "unexpected event: ".Dat
+a::Dumper->Dump([$e]);
                                }
                        }
                }
        }
}
[download]

If I use another terminal to telnet to localhost port 12345, type in "hello\n", then close the connection, i get the output

fd 3 EPOLLIN 1 EPOLLERR 8 EPOLLHUP 16

epoll said: $VAR1 = [];
epoll said: $VAR1 = [];
epoll said: $VAR1 = [
          [
            '3',
            '1'
          ]
        ];
epoll said: $VAR1 = [];
epoll said: $VAR1 = [
          [
            '5',
            '1'
          ]
        ];
client 5 said 'hello
'
epoll said: $VAR1 = [];
epoll said: $VAR1 = [
          [
            '5',
            '1'
          ]
        ];
Use of uninitialized value in concatenation (.) or string at epoll.pl 
+line 27, <GEN1> line 1.
client 5 said ''
epoll said: $VAR1 = [];
epoll said: $VAR1 = [];
[download]

fileno 3 is the server socket, 5 is the client I accept()ed. epoll_wait returns a listref of listrefs, which are  [fd, EVENT1 | EVENT2] - it reads the line "hello\n" from the client OK, then when I close the client it generates another read event ([5,1]), and I have a hack to detect the socket has gone. Do you know how to do it properly? Thanks in advance...