I haven't done much of this with Perl, but for most socket drivers the only way to detect the connection was closed by the other end is to try to read from it. If the remote end actually sends a FIN packet, you will get a specific result from the read that you can use to trigger closure on your end. Otherwise, the half open socket will remain until something triggers a network error that causes the write to fail. But you don't check the results of the send() either, so you may have missed that as well.
Bob McConnell -----Original Message----- From: Leon Meyer [mailto:lmeyer.blt...@gmail.com] Sent: Wednesday, April 28, 2010 3:29 PM To: beginners@perl.org Subject: Perl not closing TCP sockets if clients are no longer connected? The purpose of the application is to listen for a specific UDP multicast and then to forward the data to any TCP clients connected to the server. The code works fine, but I have a problem with the sockets not closing after the TCP clients disconnects. A socketsniffer utility shows the the sockets remain open and all the UDP data continues to be forwarded to the clients. The problem I believe is with the "if ($write->connected())" block as it always return true, even if the TCP client is no longer connected. I use standard Windows Telnet to connect to the server and to see the data. When I close telnet, the TCP socket is suppose to close on the server. Any reason why connected() show the connections as active even if they are not? Also, what alternative should I use then? Code: #!/usr/bin/perl use IO::Socket::Multicast; use IO::Socket; use IO::Select; my $tcp_port = "4550"; my $tcp_socket = IO::Socket::INET->new( Listen => SOMAXCONN, LocalAddr => '0.0.0.0', LocalPort => $tcp_port, Proto => 'tcp', ReuseAddr => 1, ); use Socket qw(IPPROTO_TCP TCP_NODELAY); setsockopt( $tcp_socket, IPPROTO_TCP, TCP_NODELAY, 1); use constant GROUP => '239.2.0.81'; use constant PORT => '6550'; my $udp_socket= IO::Socket::Multicast->new(Proto=>'udp',LocalPort=>PORT); $udp_socket->mcast_add(GROUP) || die "Couldn't set group: $!\n"; my $read_select = IO::Select->new(); my $write_select = IO::Select->new(); $read_select->add($tcp_socket); $read_select->add($udp_socket); ## Loop forever, reading data from the UDP socket and writing it to the ## TCP socket(s). while (1) { ## No timeout specified (see docs for IO::Select). This will block until a TCP ## client connects or we have data. my @read = $read_select->can_read(); foreach my $read (@read) { if ($read == $tcp_socket) { ## Handle connect from TCP client. Note that UDP connections are ## stateless (no accept necessary)... my $new_tcp = $read->accept(); $write_select->add($new_tcp); } elsif ($read == $udp_socket) { ## Handle data received from UDP socket... my $recv_buffer; $udp_socket->recv($recv_buffer, 1024, undef); ## Write the data read from UDP out to the TCP client(s). Again, no ## timeout. This will block until a TCP socket is writable. my @write = $write_select->can_write(); foreach my $write (@write) { ## Make sure the socket is still connected before writing. if ($write->connected()) { $write->send($recv_buffer); } else { $write_select->remove($write); close $write; } } } } } -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
