tests/choose-port.pl

   1 # -*- perl -*-
   2
   3 # Picks a random TCP port and attempts to bind it, retrying a few
   4 # times if the chosen port is in use.  This is better than just
   5 # picking a random number without checking whether it is in use (but
   6 # of course a race window still exists).
   7 #
   8 # On success, prints a port number on stdout and exits with status 0.
   9 # On failure, prints an error on stderr and exits with a nonzero status.
  10
  11 use warnings;
  12 use strict;
  13 use Socket;
  14
  15 socket(SOCK, PF_INET, SOCK_STREAM, 0) || die "socket: $!\n";
  16 for (my ($i) = 0; ; $i++) {
  17     my ($port) = int(rand(16383)) + 49152;
  18     if (bind(SOCK, sockaddr_in($port, INADDR_ANY))) {
  19         print "$port\n";
  20         exit 0;
  21     } elsif ($i < 10 && $!{EADDRINUSE}) {
  22         # Address already in use.  Try again.
  23     } else {
  24         die "bind: $!\n";
  25     }
  26 }