How can I copy a socket into an other variable - perl

Question

I have a backendserver and different clients who provide different services.
In a thread I wait for incoming TCP connections. Then they should send am message with what type they are, like a robot or a frontend.
On the backend I now wait for the connections and check what type they are, and depending on that I want it to be copied into for example a $frontendSocket:
$requestConnectionSocket = new IO::Socket::INET(...);
$frontendSocket;
sub waitForConnection {
threads->create(sub {
while(1){
$newSocket = $requestConnectionSocket->accept();
$newSocket->recv($message, 1024);
if ($message eq "Frontend")
{
$frontendSocket = $newSocket;
$frontendSocket->send("hello\n");
}
if ($message eq "Roboter")
{$robotSocket = $newSocket;}
if ($message eq "Sensor")
{$sensorSocket = $newSocket;}
}
});
}
When I runt the script, in this thread I can send the message "hello". But when I want to use the socket outside I am not able to use $frontendSocket.
I hope you understand my problem.

Answer 1

You have multiple threads accessing the same frontendSocket. This is doomed to fail. What is going to happen when one thread receives a new message (and updates the socket with it), but another thread is still working with the previous socket? Can't do this.

Answer 2

If you're using IO::Socket wouldn't you rather use the accept method from the package like:
my $newSocket = $requestConnectionSocket->accept();
This returns an object and I see no issues assigning that object to a differently named scalar reference.
Okay you updated your question with code like the above, now:
It looks like you're trying to share state in threads, have you planned your thread safety?
# http://perldoc.perl.org/threads/shared.html
use threads;
use threads::shared;
...
my ($requestConnectionSocket, $frontendSocket, $robotSocket, $sensorSocket) :shared;
sub waitForConnection {
threads->create(sub {
while(1){
my $newSocket;
{
lock($requestConnectionSocket);
$newSocket = $requestConnectionSocket->accept();
}
$newSocket->recv($message, 1024);
if ($message eq "Frontend")
{
lock($frontendSocket);
$frontendSocket = $newSocket;
$frontendSocket->send("hello\n");
}
if ($message eq "Roboter")
{lock($robotSocket); $robotSocket = $newSocket;}
if ($message eq "Sensor")
{lock($sensorSocket); $sensorSocket = $newSocket;}
}
});
}
... meanwhile, in another context ...
# I have front end work to do now, figure out if I need to lock or wait and on what.