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Planning on sending integer values through as socket, I was surprised to find PHP only supports sending strings.
I came to the conclusion the only way to do it would be to create a string that would evaluate to the same byte values as the integer I wanted to send. So (after much messing about) I created a couple of functions: one to create this 'string' and one to convert a received value back to an integer.
<?php
//Converts an integer to 'byte array' (string), default to 4 'bytes' (chars)
function int2string($int, $numbytes=4)
{
$str = "";
for ($i=0; $i < $numbytes; $i++) {
$str .= chr($int % 256);
$int = $int / 256;
}
return $str;
}
//Converts a 'byte array' (string) to integer
function string2int($str)
{
$numbytes = strlen($str);
$int = 0;
for ($i=0; $i < $numbytes; $i++) {
$int += ord($str[$i]) * pow(2, $i * 8);
}
return $int;
}
//Example
echo int2string(16705, 2); // 16-bit integer converts to two bytes: 65, 65; which in turn is 'AA'
echo string2int('AA'); //back the other way
?>
Here's a simple script for sending messages back and forth between a server and client. At this point, the code is fairly rough because once it enters the while loop, it doesn't stop but it can be modified and fixed. Enjoy.
<?php
//The Server
error_reporting(E_ALL);
$address = "127.0.0.1";
$port = "10000";
/* create a socket in the AF_INET family, using SOCK_STREAM for TCP connection */
$mysock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_bind($mysock, $address, $port);
socket_listen($mysock, 5);
$client = socket_accept($mysock);
echo "Server started, accepting connections...\n";
$i = 0;
while (true == true)
{
$i++;
echo "Sending $i to client.\n";
socket_write($client, $i, strlen($i));
$input = socket_read($client, 2048);
echo "Response from client is: $input\n";
sleep(5);
}
echo "Closing sockets...";
socket_close($client);
socket_close($mysock);
?>
<?php
//The Client
error_reporting(E_ALL);
$address = "127.0.0.1";
$port = 10000;
/* Create a TCP/IP socket. */
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "\n";
} else {
echo "socket successfully created.\n";
}
echo "Attempting to connect to '$address' on port '$port'...";
$result = socket_connect($socket, $address, $port);
if ($result === false) {
echo "socket_connect() failed.\nReason: ($result) " . socket_strerror(socket_last_error($socket)) . "\n";
} else {
echo "successfully connected to $address.\n";
}
$i = 0;
while (true == true)
{
$i++;
echo "Sending $i to server.\n";
socket_write($socket, $i, strlen($i));
$input = socket_read($socket, 2048);
echo "Response from server is: $input\n";
sleep(5);
}
echo "Closing socket...";
socket_close($socket);
?>
Another Workaround for sending UDP Broadcasts to 255.255.255.255 and receiving the responses on a specific port:
<?php
// NOTE!
// This is quick and dirty code! It comes without error handling!
// Timeout in seconds waiting for a response.
$timeout = 10;
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($sock,"0.0.0.0",10000);
socket_set_option($sock, SOL_SOCKET, SO_BROADCAST, 1);
$buf = "Hello World";
socket_sendto($sock, $buf, strlen($buf), 0, "255.255.255.255", 10000);
socket_set_block($sock);
socket_set_option($sock,
SOL_SOCKET,
SO_RCVTIMEO,
array("sec"=>10,"usec"=>0));
$timeout += time();
while (time() <= $timeout-1) {
if (($len = @socket_recvfrom($sock,$ret,2048,0,$cIP,$cPort)) != false) {
echo bin2hex($ret);
}
}
socket_set_nonblock($sock);
socket_close($sock);
?>
NOTE! If you are trying to send a broadcast-message using this code you _may_ get a "Permission denied"-Error at socket_connect, even if you are running this as root on a linux box.
<?php
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_connect($sock,"255.255.255.255", 10000);
socket_set_option($sock, SOL_SOCKET, SO_BROADCAST, 1);
$buf = "Hello World!";
socket_write($sock,$buf,strlen($buf));
socket_close($sock);
?>
The only workaround for this is to get the broadcast address of the interface and walk through all IPs with a for-loop.
I have beaten the zombies with this code:
pcntl_signal(SIGCHLD, SIG_IGN);
pcntl_signal(SIGTERM, SIG_DFL);
pcntl_signal(SIGINT, SIG_DFL);
server now exits with `kill`
At the moment (2007-09), i don't find this extension in the PECL, but instead in the usual php extension directory. It needs to be included in the php-ini:
extension = php_sockets.dll
(or ".so" - whatever for your system).
Wake on Lan , working ok without configurations, and some features
<?php
function wake_on_lan($mac,$addr=false,$port=7) {
//Usage
// $addr:
// You will send and broadcast tho this addres.
// Normaly you need to use the 255.255.255.255 adres, so i made it as default. So you don't need
// to do anything with this.
// Since 255.255.255.255 have permission denied problems you can use addr=false to get all broadcast address from ifconfig command
// addr can be array with broadcast IP values
// $mac:
// You will WAKE-UP this WOL-enabled computer, you need to add the MAC-addres here.
// Mac can be array too
//
//Return
// TRUE: When socked was created succesvolly and the message has been send.
// FALSE: Something went wrong
//
//Example 1
// When the message has been send you will see the message "Done...."
// if ( wake_on_lan('00:00:00:00:00:00'))
// echo 'Done...';
// else
// echo 'Error while sending';
//
if ($addr===false){
exec("ifconfig | grep Bcast | cut -d \":\" -f 3 | cut -d \" \" -f 1",$addr);
$addr=array_flip(array_flip($addr));
}
if(is_array($addr)){
$last_ret=false;
for ($i=0;$i<count($ret);$i++)
if ($ret[$i]!==false)
$last_ret=wake_on_lan($mac,$ret[$i],$port);
return($last_ret);
}
if (is_array($mac)){
$ret=array();
foreach($mac as $k=>v)
$ret[$k]=wake_on_lan($v,$addr,$port);
return($ret);
}
//Check if it's an real MAC-addres and split it into an array
$mac=strtoupper($mac);
if (!preg_match("/([A-F0-9]{1,2}[-:]){5}[A-F0-9]{1,2}/",$mac,$maccheck))
return false;
$addr_byte = preg_split("/[-:]/",$maccheck[0]);
//Creating hardware adress
$hw_addr = '';
for ($a=0; $a < 6; $a++)//Changing mac adres from HEXEDECIMAL to DECIMAL
$hw_addr .= chr(hexdec($addr_byte[$a]));
//Create package data
$msg = str_repeat(chr(255),6);
for ($a = 1; $a <= 16; $a++)
$msg .= $hw_addr;
//Sending data
if (function_exists('socket_create')){
//socket_create exists
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); //Can create the socket
if ($sock){
$sock_data = socket_set_option($sock, SOL_SOCKET, SO_BROADCAST, 1); //Set
if ($sock_data){
$sock_data = socket_sendto($sock, $msg, strlen($msg), 0, $addr,$port); //Send data
if ($sock_data){
socket_close($sock); //Close socket
unset($sock);
return(true);
}
}
}
@socket_close($sock);
unset($sock);
}
$sock=fsockopen("udp://" . $addr, $port);
if($sock){
$ret=fwrite($sock,$msg);
fclose($sock);
}
if($ret)
return(true);
return(false);
}
?>
For an implementation of a Socket Daemon framework that can handle both client and server sockets, async (non blocking) communication, which is flexible and easy to use see:
http://www.chabotc.nl/php/php-socket-daemon-library/
There is a fantastic book on this library called 'TCP/IP Sockets in C' (ISBN 1558608265), that covers all of the ins and outs, quirks, and everything else that goes on. It's written for C, of course, but it could have easily been written for PHP with almost no serious code differences.
Dustin
This function to send Magic Packet works really !!!
/********/
<?php
function wake($ip, $mac, $port)
{
$nic = fsockopen("udp://" . $ip, $port);
if($nic)
{
$packet = "";
for($i = 0; $i < 6; $i++)
$packet .= chr(0xFF);
for($j = 0; $j < 16; $j++)
{
for($k = 0; $k < 6; $k++)
{
$str = substr($mac, $k * 2, 2);
$dec = hexdec($str);
$packet .= chr($dec);
}
}
$ret = fwrite($nic, $packet);
fclose($nic);
if($ret)
return true;
}
return false;
}
?>
/********/
Executed with:
wake('123.123.123.123', '112233445566', 9);
Function to send Magic Packets for Wake on Wan (WOW) or Wake on Lan(WOL), without sockets library.
<?
function WakeOnLan($ip, $mac, $port)
{
$packet = "";
for($i = 0; $i < 6; $i++) $packet .= chr(0xFF);
for($i = 0; $i < 6; $i++) $packet .= chr((int)substr($mac, $i, $i + 2));
$nic = fsockopen("udp://" . $ip, $port));
if($nic==false){
return false;
fclose($nic);
}
fwrite($nic, $packet);
fclose($nic);
return true;
}
?>
If you want to use any complicated preexisting protocols, you may find the function pack (http://php.net/pack) useful.
A multicast server can be written badly as follows:
$bc_string = "Hello World!";
$sock = socket_create(AF_INET, SOCK_DGRAM, 0);
$opt_ret = socket_set_option($sock, 1, 6, TRUE);
$send_ret = socket_sendto($sock, $bc_string, strlen($bc_string), 0, '230.0.0.1', 4446);
Checking the return types is needed, but this does allow for you to multicast from php code.
I've been using the ICMP Checksum calculation function written by Khaless [at] bigpond [dot] com. But when having an odd length of data, it failed, so I made my own instead, which adds a 0 if the data length is odd:
<?php
function icmpChecksum($data)
{
// Add a 0 to the end of the data, if it's an "odd length"
if (strlen($data)%2)
$data .= "\x00";
// Let PHP do all the dirty work
$bit = unpack('n*', $data);
$sum = array_sum($bit);
// Stolen from: Khaless [at] bigpond [dot] com
// The code from the original ping program:
// sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
// sum += (sum >> 16); /* add carry */
// which also works fine, but it seems to me that
// Khaless will work on large data.
while ($sum>>16)
$sum = ($sum >> 16) + ($sum & 0xffff);
return pack('n*', ~$sum);
}
?>
Very good step-by-step tutorial for a network daemon is here:
http://www.php-mag.net/itr/online_artikel [next]
[before] /psecom,id,484,nodeid,114.html
Sorry, I was forced to split this link. :-(
hexdump() is a fantastic function for "dumping" packets or binary output from servers. See the below link for more information.
http://aidanlister.com/repos/v/function.hexdump.php
Here another socketclass which can handle the most importand things.
http://kacke.de/php_samples/source.php?f=socke.inc
Here a little Chatserver based on this class.
http://kacke.de/php_samples/source.php?f=pline.php
Maybe its helpful :)
Toppi
A little example that shows how to implement a simple multi-client iterative server (without forking). Launch the server and connect multiple telnet clients on it. It's a basic chat program.
#!/usr/bin/php -q
<?php
error_reporting(E_ALL);
set_time_limit(0);
ob_implicit_flush();
$address = '127.0.0.1';
$port = 8888;
function handle_client($allclient, $socket, $buf, $bytes) {
foreach($allclient as $client) {
socket_write($client, "$socket wrote: $buf");
}
}
if (($master = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) < 0) {
echo "socket_create() failed: reason: " . socket_strerror($master) . "\n";
}
socket_set_option($master, SOL_SOCKET,SO_REUSEADDR, 1);
if (($ret = socket_bind($master, $address, $port)) < 0) {
echo "socket_bind() failed: reason: " . socket_strerror($ret) . "\n";
}
if (($ret = socket_listen($master, 5)) < 0) {
echo "socket_listen() failed: reason: " . socket_strerror($ret) . "\n";
}
$read_sockets = array($master);
while (true) {
$changed_sockets = $read_sockets;
$num_changed_sockets = socket_select($changed_sockets, $write = NULL, $except = NULL, NULL);
foreach($changed_sockets as $socket) {
if ($socket == $master) {
if (($client = socket_accept($master)) < 0) {
echo "socket_accept() failed: reason: " . socket_strerror($msgsock) . "\n";
continue;
} else {
array_push($read_sockets, $client);
}
} else {
$bytes = socket_recv($socket, $buffer, 2048, 0);
if ($bytes == 0) {
$index = array_search($socket, $read_sockets);
unset($read_sockets[$index]);
socket_close($socket);
} else {
$allclients = $read_sockets;
array_shift($allclients); // remove master
handle_client($allclients, $socket, $buffer, $bytes);
}
}
}
}
?>
I have searched long and hard for a ping script that does NOT use EXEC() or SYSTEM(). So far, I have found nothing, so I decided to write my own, which was a task to say the least.
First off, I would like to thank Khaless for their checksum function, converting it from C looked like a task in itself.
Here is the class I wrote
<?php
class Net_Ping
{
var $icmp_socket;
var $request;
var $request_len;
var $reply;
var $errstr;
var $time;
var $timer_start_time;
function Net_Ping()
{
$this->icmp_socket = socket_create(AF_INET, SOCK_RAW, 1);
socket_set_block($this->icmp_socket);
}
function ip_checksum($data)
{
for($i=0;$i<strlen($data);$i += 2)
{
if($data[$i+1]) $bits = unpack('n*',$data[$i].$data[$i+1]);
else $bits = unpack('C*',$data[$i]);
$sum += $bits[1];
}
while ($sum>>16) $sum = ($sum & 0xffff) + ($sum >> 16);
$checksum = pack('n1',~$sum);
return $checksum;
}
function start_time()
{
$this->timer_start_time = microtime();
}
function get_time($acc=2)
{
// format start time
$start_time = explode (" ", $this->timer_start_time);
$start_time = $start_time[1] + $start_time[0];
// get and format end time
$end_time = explode (" ", microtime());
$end_time = $end_time[1] + $end_time[0];
return number_format ($end_time - $start_time, $acc);
}
function Build_Packet()
{
$data = "abcdefghijklmnopqrstuvwabcdefghi"; // the actual test data
$type = "\x08"; // 8 echo message; 0 echo reply message
$code = "\x00"; // always 0 for this program
$chksm = "\x00\x00"; // generate checksum for icmp request
$id = "\x00\x00"; // we will have to work with this later
$sqn = "\x00\x00"; // we will have to work with this later
// now we need to change the checksum to the real checksum
$chksm = $this->ip_checksum($type.$code.$chksm.$id.$sqn.$data);
// now lets build the actual icmp packet
$this->request = $type.$code.$chksm.$id.$sqn.$data;
$this->request_len = strlen($this->request);
}
function Ping($dst_addr,$timeout=5,$percision=3)
{
// lets catch dumb people
if ((int)$timeout <= 0) $timeout=5;
if ((int)$percision <= 0) $percision=3;
// set the timeout
socket_set_option($this->icmp_socket,
SOL_SOCKET, // socket level
SO_RCVTIMEO, // timeout option
array(
"sec"=>$timeout, // Timeout in seconds
"usec"=>0 // I assume timeout in microseconds
)
);
if ($dst_addr)
{
if (@socket_connect($this->icmp_socket, $dst_addr, NULL))
{
} else {
$this->errstr = "Cannot connect to $dst_addr";
return FALSE;
}
$this->Build_Packet();
$this->start_time();
socket_write($this->icmp_socket, $this->request, $this->request_len);
if (@socket_recv($this->icmp_socket, &$this->reply, 256, 0))
{
$this->time = $this->get_time($percision);
return $this->time;
} else {
$this->errstr = "Timed out";
return FALSE;
}
} else {
$this->errstr = "Destination address not specified";
return FALSE;
}
}
}
$ping = new Net_Ping;
$ping->ping("www.google.ca");
if ($ping->time)
echo "Time: ".$ping->time;
else
echo $ping->errstr;
?>
Hope this saves some troubles.
noSanity
I spent a while trying to use SOCK_RAW to send ICMP request packets so i could ping. This however lead me to need the internet checksum written as a php function, which was a little hard because of the way PHP handles variable types. Anyway, to save others the effort heres what i came up with, this returns Checksum for $data
<?PHP
// Computes Internet Checksum for $data
// will return a 16-bit internet checksum for $data
function inetChecksum($data)
{
// 32-bit accumilator, 16 bits at a time, adds odd bit on at end
for($i=0;$i<strlen($data);$i += 2)
{
if($data[$i+1]) $bits = unpack('n*',$data[$i].$data[$i+1]);
else $bits = unpack('C*',$data[$i]);
$sum += $bits[1];
}
// Fold 32-bit sum to 16 bits
while ($sum>>16) $sum = ($sum & 0xffff) + ($sum >> 16);
$checksum = pack('n1',~$sum);
return $checksum;
}
?>
And with this i was able to construct a correct PING Request.
>The function, that send the WakeOnLan (WOL, Magic packet) signal:
<?php
# Wake on LAN - (c) HotKey (at SPR dot AT), upgraded by Murzik <tomurzik@inbox.ru>
flush();
function WakeOnLan($addr, $mac)
{
$addr_byte = explode(':', $mac);
$hw_addr = '';
for ($a=0; $a < 6; $a++) $hw_addr .= chr(hexdec($addr_byte[$a]));
$msg = chr(255).chr(255).chr(255).chr(255).chr(255).chr(255);
for ($a = 1; $a <= 16; $a++) $msg .= $hw_addr;
// send it to the broadcast address using UDP
// SQL_BROADCAST option isn't help!!
$s = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
if ($s == false)
{
echo "Error creating socket!\n";
echo "Error code is '".socket_last_error($s)."' - " . socket_strerror(socket_last_error($s));
}
else
{
// setting a broadcast option to socket:
$opt_ret = socket_set_option($s, 1, 6, TRUE);
if($opt_ret < 0)
{
echo "setsockopt() failed, error: " . strerror($opt_ret) . "\n";
}
$e = socket_sendto($s, $msg, strlen($msg), 0, $addr, 2050);
socket_close($s);
echo "Magic Packet sent (".$e.") to ".$addr.", MAC=".$mac;
}
}
#WakeOnLan('yourIPorDomain.dyndns.org', 'your:MAC:address');
#WakeOnLan('192.168.0.2', '00:30:84:2A:90:42');
#WakeOnLan('192.168.1.2', '00:05:1C:10:04:05');
//if you have switch or other routing devices in LAN, sendign to
// the local IP isn't helps! you need send to the broadcast address like this:
WakeOnLan('192.168.1.255', '00:05:1C:10:04:05');
?>
I have spent the past two days ripping out hair trying to figure out how to prevent zombie processes w/the examples above and I just happend to find this in the manual for another lanuage, felt it neccassry to port it here.
--begin copy--
van[at]webfreshener[dot]com
11-Oct-2002 02:53
Forking your PHP daemon will cause it to zombie on exit.
...or so I've seen on:
FreeBSD (PHP4.2.x)
Debian (PHP4.3.0-dev)
Darwin (PHP4.3.0-dev)
This was tested with the example code above and other scripts created for evaluation.
Seems adding <b>--enable-sigchild</b> to your configure will get rid of the problem.
Hope that saves some hair tearing :]
--end copy--
Thanks vam@wenfreshener.com !!!!
I found this EXTREMELY useful link on the zend php
mailing list:
http://www.zend.com/lists/php-dev/200205/msg00286.html
It's about being able to use multiple connections
in a php socket server, WITHOUT having
to use those threads everyone seems to be
so very fond of.
works very well :)
(ps: i didn't make it, so....don't say thanks to me ;),
thank him)
"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.
http://www.ecst.csuchico.edu/~beej/guide/net/
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);
}
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) . "<BR>\n"; }
// be sure to close your socket when you're done
close($sock);
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