In terms of networking, the most basic thing is BSD socket programming, but often when getting started with perl, the most troublesome thing is undoubtedly how to start and how to Step by step. The best prescription is Example, a complete piece of code that can be run (worked) and can be felt through practice much more profound than looking at boring manual.
The following are several server/client written using Socket and IO::Socket. They can implement the simplest but most basic tasks, including a forking/accept model. You can directly copy these codes and then add small modifications to develop some small tcp/udp applications.
TCP client, Socket module
Introduction: Implementing reading a line of information from the server and then returning it
#!/usr/bin/perl -w
# tcp_socket_cli.pl
use strict;
use Socket;
my $addr = $ARGV[0] || '127.0.0.1';
my $port = $ARGV[1] || '3000';
my $dest = sockaddr_in($port, inet_aton($addr));
my $buf = undef;
socket(SOCK,PF_INET,SOCK_STREAM,6) or die "Can't create socket: $!";
connect(SOCK,$dest) or die "Can't connect: $!";
my $bs = sysread(SOCK, $buf, 2048); # try to read 2048
print "Received $bs bytes, content $buf\n"; # actually get $bs bytes
close SOCK;
Execution results:
perl tcp_socket_cli.pl localhost 25
Received 41 bytes, content 220 ESMTP Postfix - ExtMail 0.12-hzqbbc
TCP server Socket module, forking/accept model
Introduction: A multi-process TCP server, the function of daytime is implemented in sample
#!/usr/bin/perl -w
# tcp_socket_dt_srv.pl
use strict;
use Socket;
use IO::Handle;
use POSIX qw(WNOHANG);
my $port = $ARGV[0] || '3000';
my $proto = getprotobyname('tcp');
$SIG{'CHLD'} = sub {
while((my $pid = waitpid(-1, WNOHANG)) >0) {
print "Reaped child $pid\n";
}
};
socket(SOCK, AF_INET, SOCK_STREAM, getprotobyname('tcp'))
or die "socket() failed: $!";
setsockopt(SOCK,SOL_SOCKET,SO_REUSEADDR,1)
or die "Can't set SO_REUSADDR: $!" ;
my $my_addr = sockaddr_in($port,INADDR_ANY);
bind(SOCK,$my_addr) or die "bind() failed: $!";
listen(SOCK,SOMAXCONN) or die "listen() failed: $!";
warn "Starting server on port $port...\n";
while (1) {
next unless my $remote_addr = accept(SESSION,SOCK);
defined(my $pid=fork) or die "Can't fork: $!\n";
if($pid==0) {
my ($port,$hisaddr) = sockaddr_in($remote_addr);
warn "Connection from [",inet_ntoa($hisaddr),",$port]\n";
SESSION->autoflush(1);
print SESSION (my $s = localtime);
warn "Connection from [",inet_ntoa($hisaddr),",$port] finished\n";
close SESSION;
exit 0;
}else {
print "Forking child $pid\n";
}
}
close SOCK;
Use the above tcp_socket_cli.pl to access the execution results of this server:
[hzqbbc@local misc]$ perl tcp_socket_dt_srv.pl
Starting server on port 3000...
Connection from [127.0.0.1,32888]
Connection from [127.0.0.1,32888] finished
Reaped child 13927
Forking child 13927
TCP client, IO::Sockiet module
Introduction: Also a client, but using the IO::Socket object-oriented module
#!/usr/bin/perl -w
# tcp_iosocket_cli.pl
use strict;
use IO::Socket;
my $addr = $ARGV[0] || '127.0.0.1';
my $port = $ARGV[1] || '3000';
my $buf = undef;
my $sock = IO::Socket::INET->new(
PeerAddr => $addr,
PeerPort => $port,
Proto => 'tcp')
or die "Can't connect: $!\n";
$buf = <$sock>;
my $bs = length($buf);
print "Received $bs bytes, content $buf\n"; # actually get $bs bytes
close $sock;
TCP server, IO::Socket module, forking/accept model
Introduction: The same daytime
Server, rewrite using IO::Socket.
#!/usr/bin/perl
# tcp_iosocket_dt_srv.pl
use strict;
use IO::Socket;
use POSIX qw(WNOHANG);
$SIG = sub {
while((my $pid = waitpid(-1, WNOHANG)) >0) {
print "Reaped child $pid\n";
}
};
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 $s = localtime), "\n";
warn "Connection from [$peer,$port] finished\n";
close $session;
exit 0;
}else {
print "Forking child $pid\n";
}
}
close $sock;
Now let’s introduce the use of Socket and IO::Socket modules to carry out client/server development of Unix domain Socket. Unix Domain Socket (referred to as unix socket) has several advantages compared to INET-type sockets such as TCP/UDP:
1) High security, unix socket is only used in a stand-alone environment and does not support communication between machines.
2) High efficiency, the execution speed is about twice that of TCP, and is mostly used for internal operating system communication (IPC)
3) Support SOCK_DGRAM, but unlike UDP, the front and back messages are strictly ordered
Therefore, using Unix sockets to design stand-alone IPC applications is the first choice. Very practical. A large number of Unix application software use unix sockets for inter-program communication.
Unix Domain Socket Client, Socket Module
Introduction: A client using Unix domain socket.
#!/usr/bin/perl -w
use strict;
use Socket;
use IO::Handle;
my $path = $ARGV[0] || '/tmp/';
socket(my $sock, PF_UNIX, SOCK_STREAM, 0);
my $sun = sockaddr_un($path);
connect($sock, $sun) or die "Connect: $!\n";
$sock->autoflush(1);
my $buf = <$sock>;
my $bs = length($buf);
print "Received $bs bytes, content $buf\n";
close $sock;
Unix Domain Socket Server, Socket Module
Introduction: A daytime server implemented using Unix domain socket.
#!/usr/bin/perl -w
# tcp_socket_dt_srv.pl
use strict;
use Socket;
use IO::Handle;
use POSIX qw(WNOHANG);
my $path = $ARGV[0] || '/tmp/';
$SIG{'CHLD'} = sub {
while((my $pid = waitpid(-1, WNOHANG)) >0) {
print "Reaped child $pid\n";
}
};
socket(SOCK, PF_UNIX, SOCK_STREAM, 0)
or die "socket() failed: $!";
setsockopt(SOCK,SOL_SOCKET,SO_REUSEADDR,1)
or die "Can't set SO_REUSADDR: $!" ;
unlink $path if -r $path;
bind(SOCK,sockaddr_un($path)) or die "bind() failed: $!";
listen(SOCK,SOMAXCONN) or die "listen() failed: $!";
warn "Starting server on path $path...\n";
while (1) {
next unless my $sockname = accept(SESSION,SOCK);
defined (my $pid=fork) or die "Can't fork: $!\n";
if($pid==0) {
SESSION->autoflush(1);
print SESSION (my $s = localtime);
close SESSION;
exit 0;
}else {
print "Forking child $pid\n";
}
}
close SOCK;