--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/client6.pl	Fri Feb 09 14:19:11 2018 +0900
@@ -0,0 +1,45 @@
+#!/usr/bin/perl -w
+# require 5.002;
+use strict;
+use Socket qw (getaddrinfo getnameinfo AF_UNSPEC SOCK_STREAM SOL_SOCKET SO_REUSEADDR NI_NUMERICHOST NI_NUMERICSERV ) ;
+my ($remote,$port, $iaddr, $paddr, $proto, $line);
+
+my $user = getpwuid($<);
+
+$remote  = shift || 'localhost';
+$port    = shift || 2345;  # random port
+if ($port =~ /\D/) { $port = getservbyname($port, 'tcp') }
+die "No port" unless $port;
+
+&connect_address($remote,$port);
+
+syswrite SOCK, "$user\n"; #  or die "syswrite $!\n";
+while (<SOCK>) {
+    print ;
+}
+
+close SOCK           or die "close: $!";
+
+
+sub connect_address {
+    my ($host0,$port0) = @_;
+
+    my ($err,@res) = getaddrinfo($host0, $port0, {socktype=>SOCK_STREAM});
+    my $family1 = -1;
+    my ($err1, $host, $port);
+    for my $res (@res) { 
+        my ($family, $socktype, $proto, $saddr, $canonname) = ( $res->{family} , $res->{socktype}, $res->{protocol}, $res->{addr}, $res->{canonname} );
+
+        ($err1, $host, $port) = getnameinfo($saddr,NI_NUMERICHOST | NI_NUMERICSERV);
+        print STDERR "Trying to connect to $host : $port...\n";
+
+        socket(SOCK, $family, $socktype, $proto) || next;
+        if (connect(SOCK, $saddr)) { 
+            print STDERR "connected to $host port $port\n";
+            return;
+        }
+        close(SOCK);
+    }
+    die "connect attempt failed\n";
+}
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/server6.pl	Fri Feb 09 14:19:11 2018 +0900
@@ -0,0 +1,87 @@
+#!/usr/bin/perl 
+# require 5.002;
+
+use strict;
+BEGIN { $ENV{PATH} = '/usr/ucb:/bin' }
+use Socket qw( 
+   getaddrinfo getnameinfo IN6ADDR_ANY AF_UNSPEC SOCK_STREAM PF_UNSPEC 
+   AI_PASSIVE NI_NUMERICHOST  NI_NUMERICSERV SOL_SOCKET SO_REUSEADDR SOMAXCONN
+);
+
+use Carp;
+use IO::Select;
+
+my $myself = "$0 ";
+sub logmsg { print "$myself $$: @_ at ", scalar localtime, "\n" }
+
+my $host = shift || IN6ADDR_ANY;
+my $port = shift || 2345;
+my $proto = getprotobyname('tcp');
+
+my $select = &bind_sockets($host,$port);
+
+logmsg "server started on port $port";
+
+my %address_list;
+
+my $paddr;
+
+while(my @ready = $select->can_read()) {
+    for my $socket ( @ready ) {
+        my $paddr =  accept(my $client, $socket);
+        next if (! $paddr) ;
+
+        my ($err,$addr,$m) = getnameinfo($paddr,NI_NUMERICHOST); 
+        my ($err,$name,$port) = getnameinfo($paddr,NI_NUMERICSERV); 
+        $address_list{$addr} = $name;
+
+        my $user = <$client>;
+        $user=~ s/[\r\n]//g;
+        logmsg "connection from $user \@ $name [",
+             $addr, "]
+             at port $port";
+
+        print $client "Hello there, $name, it's now ",
+	scalar localtime, "\n";
+        foreach my $k (keys %address_list) {
+            print $client "$k = $address_list{$k}\n";
+        }
+        close($client);
+    }
+}
+
+sub bind_sockets {
+    my ($host0,$port0) = @_;
+    my $select = IO::Select->new();
+
+    my ($err,@res) = getaddrinfo($host0, $port0,{socktype=>SOCK_STREAM, flags=>AI_PASSIVE});
+    my @socket;
+    my (@host);
+    for my $res (@res) { 
+        my ($family, $socktype, $proto, $saddr, $canonname) = ( $res->{family} , $res->{socktype}, $res->{protocol}, $res->{addr}, $res->{canonname} );
+        my ($host, $port) = getnameinfo($saddr,NI_NUMERICHOST | NI_NUMERICSERV);
+        print STDERR "Trying to bind to $host : $port... ";
+        socket(my $fd, $family, $socktype, $proto) || next;
+        setsockopt($fd, SOL_SOCKET, SO_REUSEADDR, pack("l", 1))   || die "setsockopt : $!";
+
+        if (bind($fd, $saddr)) { # sockaddr_in($port, INADDR_ANY)
+            listen($fd,SOMAXCONN)  || die "listen: $!  ";
+            $select->add($fd);
+            print STDERR "connected.\n";
+        } else {
+            print STDERR "failed.\n";
+            close($fd);
+        }
+    }
+
+    if ($select->count == 0) {
+        die "connect attempt failed\n";
+    }
+    return $select;
+
+}
+
+
+sub accepts {
+    my ($c, @sockets) = @_;    # $c is dummy
+}