Hello again beanscake,

Since you are running on MacOS and you have by default grep(1) - Linux man page and all sweet linux network tools nc(1) - Linux man page, why do not implement your own way of checking active tcp/udp ports based on the server port.

Sample of code with output:

#!/usr/bin/perl 
use warnings;
use strict;
use Data::Dumper;

my $serverPort = 12345;

my @ActivePorts = `netstat -a | grep $serverPort`;

# Strip white spaces
@ActivePorts = map { s/^\s+|\s+$//g; $_; } @ActivePorts;

print Dumper \@ActivePorts;

__END__

$VAR1 = [
          'udp        0      0 localhost:12345         *:*'
        ];
[download]

I am running a UDP server localy at the moment and I can see the active port that listens to my connections.

So based on the output you can either terminate them or simply use them.

Update: Even faster than nc is ss(8) - Linux man page that provides you also pid without sudo.

Sample of code with output:

#!/usr/bin/perl 
use warnings;
use strict;
use Data::Dumper;

my $serverPort = 12345;

my @ActivePorts = `ss -lp | grep 12345`;

# Strip white spaces
@ActivePorts = map { s/^\s+|\s+$//g; $_; } @ActivePorts;

print Dumper \@ActivePorts;

__END__

$VAR1 = [
          'tcp    UNCONN     0      0            127.0.0.1:ipproto-123
+45               *:*        users:(("perl",8179,3))'
        ];
[download]

Hope this helps.