You want to connect to a socket on a remote machine.
This solution assumes you're using the Internet to communicate. For TCP-like communication within a single machine, see Recipe 17.6.
use IO::Socket; $socket = IO::Socket::INET->new(PeerAddr => $remote_host, PeerPort => $remote_port, Proto => "tcp", Type => SOCK_STREAM) or die "Couldn't connect to $remote_host:$remote_port : $@\n"; # ... do something with the socket print $socket "Why don't you call me anymore?\n"; $answer = <$socket>; # and terminate the connection when we're done close($socket);
or create a socket by hand for better control:
use Socket; # create a socket socket(TO_SERVER, PF_INET, SOCK_STREAM, getprotobyname('tcp')); # build the address of the remote machine $internet_addr = inet_aton($remote_host) or die "Couldn't convert $remote_host into an Internet address: $!\n"; $paddr = sockaddr_in($remote_port, $internet_addr); # connect connect(TO_SERVER, $paddr) or die "Couldn't connect to $remote_host:$remote_port : $!\n"; # ... do something with the socket print TO_SERVER "Why don't you call me anymore?\n"; # and terminate the connection when we're done close(TO_SERVER);
While coding this by hand requires a lot of steps, the IO::Socket::INET class wraps them all in a convenient constructor. The important things to know are where you're going (the PeerAddr and PeerPort parameters) and how you're getting there (the Type parameter). IO::Socket::INET tries to determine these things from what you've given it. It deduces Proto from the Type and Port if possible, and assumes
PeerAddr is a string containing either a hostname (
"www.oreilly.com") or an IP address (
"220.127.116.11"). PeerPort is an integer, the port number to connect to. You can embed the port number in the address by giving an address like
"www.oreilly.com:80". Type is the kind of socket to create: SOCK_DGRAM for datagrams, or SOCK_STREAM for streams.
If you want a SOCK_STREAM connection to a port on a particular machine with no other options, pass a single string to
IO::Socket::INET->new consisting of the hostname and port separated by a colon:
$client = IO::Socket::INET->new("www.yahoo.com:80") or die $@;
If an error occurs, IO::Socket::INET will return
$!) will be set to the error message.
$s = IO::Socket::INET->new(PeerAddr => "Does not Exist", Peerport => 80, Type => SOCK_STREAM ) or die $@;
If your packets are disappearing into a network void, it can take a while for your inability to connect to a port to be recognized. You can decrease this time by specifying a
Timeout parameter to
$s = IO::Socket::INET->new(PeerAddr => "bad.host.com", PeerPort => 80, Type => SOCK_STREAM, Timeout => 5 ) or die $@;
If you do this, though, there's no way to tell from
$@ whether you couldn't connect or whether you timed out. Sometimes it's better to set it up by hand instead of using a module.
INADDR_ANY is a special address, meaning "listen on any interface." If you want to restrict it to a particular IP address, add a
LocalAddr parameter to your call to
IO::Socket::INET->new. If coding by hand code, do this:
$inet_addr = inet_aton("18.104.22.168"); $paddr = sockaddr_in($port, $inet_addr); bind(SOCKET, $paddr) or die "bind: $!";
If you know only the name, do this:
gethostbyname functions in Chapter 3 of Programming Perl and in perlfunc (1); the documentation for the standard Socket, IO::Socket, and Net::hostent modules; the section on
"Internet TCP Clients and Servers"
in Chapter 6 of Programming Perl and in perlipc (1); Unix Network Programming, by W. Richard Stevens, published by Prentice Hall (1992); Recipe 17.2; Recipe 17.3