该应用程序的目的是侦听特定的UDP多播,然后将数据转发给连接到服务器的任何TCP客户端。该代码工作正常,但我有问题的TCP客户端断开后,套接字不关闭。 socketsniffer实用程序显示套接字保持打开状态,并且所有UDP数据继续被转发给客户端。我相信问题在于“if($ write-> connected())”块,因为它总是返回true,即使TCP客户端不再连接。我使用标准Windows Telnet连接到服务器并查看数据。当我关闭telnet时,假设TCP套接字在服务器上关闭。如果客户端不再连接,Perl不关闭TCP套接字?
为什么connect()将连接显示为活动连接的任何原因,即使它们不是?另外,我应该使用什么替代方案?
代码:
#!/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;
}
}
}
}
}
即使检查零字节的读写,也不会告诉你TCP套接字是否仍然连接,而不知道另一端有什么(例如,当我发送“foo”时,我总是会收到“bar “在3秒内)。 – mob 2010-04-28 19:16:57
读或写完成时读取或写入的零字节会告诉您另一端发送FIN。你是对的,在没有保持联系的情况下,不可能确定另一端是否已经离开而不关闭连接。 – Stewart 2010-04-28 19:56:06