args to specify port and set auto-port mode
can now specify -p $port to specify a custom port number
auto-port is useful when you share a file with one person then need to share another file with someone else and the first person hasn't used the link yet

Unfortunately, there is a problem with my Getopt::Std call for some reason, despite passing 'ap:', the -a arg wants to consume an argument so for now I'm doing:
```otfile -a yes some_file```
Need to do more testing to determine whose fault it is