perl tcp服务器端编程，接收客户端信息并处理后发送响应给客户端

#!/usr/bin/perl
# tcp_iosocket_dt_srv.pl
use strict;
use IO::Socket;
use POSIX qw(WNOHANG);

$SIG{CHLD} = sub {
     while((my $pid = waitpid(-1, WNOHANG)) >0) {
          print "Reaped child $pid\n";
      }
};


#my $zombies = 0;
#$SIG{CHLD} = sub {$zombies++;};

my $port = $ARGV[0] || '3000';
my $sock = IO::Socket::INET->new( Listen => 20,
                                  LocalPort => $port,
                                  Timeout => 60*1,
                                  Reuse => 1)
  or die "Can't create listening socket: $!\n";

warn "Starting server on port $port...\n";
while (1) {
     next unless my $session = $sock->accept;
     defined (my $pid = fork) or die "Can't fork: $!\n";



     if($pid == 0) {
          my $peer = gethostbyaddr($session->peeraddr,AF_INET) || $session->peerhost;
          my $port = $session->peerport;
          warn "Connection from [$peer,$port]\n";
          $session->autoflush(1);
          #print $session (my $s = localtime), "\n";
          #print $session "OK  shumeiShumei2018\n";
          sysread $session, my $handshake_req,1024;
          print "First req: $handshake_req\n";
          my($handshake_resp) = handshake($handshake_req);
          print "resp: $handshake_resp\n";
          print $session $handshake_resp;
          warn "Connection from [$peer,$port] finished\n";
          close $session;
          exit 0;
      }else {
          print "Forking child $pid\n";
      }
close $sock;

### sub routines
#
sub handshake {
    my $req = shift;
    if ( $req =~ /sentry/) {
        return ("OK  sentry");
    } elsif ( $req =~ /saas/ ) {
        return ("OK  saas");
    } elsif ( $req =~ /data/ ) {
        return ("OK  data");
    } elsif ( $req =~ /his/ ) {
        return ("OK  his");
    } elsif ( $req =~ /bill/ ) {
        return ("OK  bill");
    } else {
        return ("OK  shumeiShumei2016");
    }
    return ("req:$req");
}