XCV. Socket functions

After several hours of working with sockets in an attempt to do UDP
broadcasting, I thought a little help was in order for anyone else looking
to do something similar, since it uses a number of those
"undocumented" functions.  Here's how I did it:

<?php
	// here is a basic opening of the a socket.  AF_INET specifies the
internet domain.  SOCK_DGRAM 
// specifies the Datagram socket type the 0 specifies that I want to use
the default protcol (which in this
// case is UDP)
	$sock = socket(AF_INET, SOCK_DGRAM, 0);

	// if the file handle assigned to socket is less than 0 then opening the
socket failed
	if($sock < 0)
	{
		echo "socket() failed, error: " . strerror($sock) .
"\n";
	}

	// here's where I set the socket options, this is essential to allow
broadcasting.  An earlier comment (as of 
// June 4th, 2001) explains what the parameters are.  For my purposes (UDP
broadcasting) I need to set 
// the broadcast option at the socket level to true.  In C, this done
using SOL_SOCKET as the level param
// (2) and SO_BROADCAST as the type param (3).  These may exist in PHP but
I couldn't reference them  
// so I used the values that referencing these variables in C returns
(namely 1 and 6 respectively).  This 
// function is basically just a wrapper to the C  function so check out
the C documentation for more info
	$opt_ret = setsockopt($sock, 1, 6, TRUE);

	// if the return value is less than one, an error occured setting the
options 
	if($opt_ret < 0)
	{
		echo "setsockopt() failed, error: " . strerror($opt_ret) .
"\n";
	}

	// finally I am ready to broad cast something.  The sendto function
allows this without any 
// connections (essential for broadcasting).  So, this function sends the
contents of $broadcast_string to the
// general broadcast address (255.255.255.255) on port 4096.  The 0 (param
4) specifies no special
// options, you can read about the options with man sendto 
	$send_ret = sendto($sock, $broadcast_string, strlen($broadcast_string),
0, '255.255.255.255', 4096);

// if the return value is less than 0, an error has occured 
	if($send_ret < 0)
	{
	echo "sendto() failed, error: " . strerror($send_ret) .
"
\n";			}
// be sure to close your socket when you're done 
close($sock);

Below is a simple forked daemon I wrote in PHP. I haven't seen one yet
anywhere else, so I thought some people might be wondering how to do  it.
Execute 
with php -q <file>

<?PHP

/*

	PHP forked daemon
	Standalone PHP binary must be compiled with --enable-sockets and
--enable-pcntl
	Dave M. -2002
        Online Services USA
*/

function sig_handler($signo) {

     switch($signo) {
         case SIGTERM:
             // handle shutdown tasks
             exit;
             break;
         case SIGHUP:
             // handle restart tasks
             break;
         case SIGUSR1:
             print "Caught SIGUSR1...\n";
             break;
         case SIGCHLD:
         	while( pcntl_waitpid(-1,$status,WNOHANG)>0 ) { 
         	}
         	break;
         case SIGINT:
		exit;
         default:
             // not implemented yet...
             break;
     }

}

function interact($sock) {

	// Custom code goes here... e.g: socket_read() socket_write()...

}

function become_daemon() {

	$child = pcntl_fork();
	if($child) {
		exit; // kill parent
	}
	posix_setsid(); // become session leader
	chdir("/");
	umask(0); // clear umask
	return posix_getpid();

}

function open_pid_file($file) {

	if(file_exists($file)) {
		$fp = fopen($file,"r");
		$pid = fgets($fp,1024);
		fclose($fp);
		if(posix_kill($pid,0)) {
			print "Server already running with PID: $pid\n";
			exit;
		}
		print "Removing PID file for defunct server process $pid\n";
		if(!unlink($file)) {
			print "Cannot unlink PID file $file\n";
			exit;
		}
	}
	if($fp = fopen($file,"w")) {
		return $fp;
	} else {
		print "Unable to open PID file $file for writing...\n";
		exit;
	}
}

function change_identity($uid,$gid) {
	global $pid_file;
	if(!posix_setgid($gid)) {
		print "Unable to setgid to $gid!\n";
		unlink($pid_file);
		exit;
	}	
	if(!posix_setuid($uid)) {
		print "Unable to setuid to $uid!\n";
		unlink($pid_file);
		exit;
	}
	
	
}

error_reporting (4);

set_time_limit (0);

ob_implicit_flush ();

$pid_file = '/tmp/php_daemon.pid';

$underpriv_uid = '99'; // uid 99 == user nobody, at least on my system.
$underpriv_gid = '99';

$port = 10000;
$address = 0; // 0 binds to all addresses, may not work on fbsd

$quit = 0;

pcntl_signal(SIGCHLD, "sig_handler");
pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGINT, "sig_handler");

$fh = open_pid_file($pid_file);

if (($sock = socket_create (AF_INET, SOCK_STREAM, 0)) < 0) {
    print "socket_create() failed: reason: " . socket_strerror
($sock) . "\n";
}

if (($ret = socket_bind ($sock, $address, $port)) < 0) {
    print "socket_bind() failed: reason: " . socket_strerror
($ret) . "\n";
}

if (($ret = socket_listen ($sock, 0)) < 0) {
    print "socket_listen() failed: reason: " . socket_strerror
($ret) . "\n";
}

change_identity($underpriv_uid,$underpriv_gid);

print "Server ready. Waiting for connections.....\n";

$pid = become_daemon();
fputs($fh,$pid);
fclose($fh);

while(!$quit) {

	if (($connection = socket_accept($sock)) < 0) {
		next;
	}
	
	if( ($child = pcntl_fork()) == -1 ) {
		print  "Could not fork!!\n";
		print "Dying...\n";
		$quit++;
	}
	elseif($child == 0) {
		socket_close($sock);
		interact($connection);
		exit;
	}
	
	socket_close($connection);
	
}

if(posix_getpid() == $pid) {
	unlink($pid_file);
}

"Beej's Guide to Network Programming" is an absolutely excellent
and easy to understand tutorial to socket programming. It was written for
C developers, but as the socket functions in PHP are (almost) analoguous,
this should not be a problem.

Although this is not the primary use of PHP, writing a server daemon in PHP
is easily feasible. 

The most advanced webserver I've seen so far (with an incredible
feature-list) is nanoweb:

  

<advertizing>

I'm trying to do the same thing, but I'm less advanced than nanoweb. My
primary goal is to create a "framework" on top other developers
should be able to easily create *any* server. Feel free to join the
project :)

  

</advertizing>

On Windows it's also possible to use sockets

Just open your PHP.ini and look for the following part:

;extension=extensions\php_sockets.dll

Unmark it like this

extension=extensions\php_sockets.dll

and there's Sockets to be build in your programs

Hello,
I use this script to get files from remote location but...:

$fp = fsockopen ($address, 80, $errno, $errstr, 30);
$newfile = fopen($newfile,"w") or DIE ("Error while
creating new file"); 
if (!$fp) {
    echo "$errstr ($errno)
\n";
} else {
    fputs ($fp, "GET /".$file." HTTP/1.0\n\r
	        Host: $mysite\n\r\n\r");

	while (!feof($fp)) {
        $record=fgets ($fp,128);
			fputs ($newfile, $record);
			echo $record;

    }
    fclose ($fp);
	fclose($newfile);
}

...i have a file with header response, and i dont know how to get
"clear" files...
Any suggest?

Unfortunately the very important function
socket_setopt() for socket options is not yet
documented in this manual!

bool socket_setopt (resource socket, int level, int optname, int )

It is very similar to setsockopt() in C!

Great, that warning about versions. No I use 4.1.2 and can only use the
function socket_clear_error (PHP 4 >= 4.2.0). The rest is 4.1.0. I'm
impressed!
Billy