Creating a server with socket functions

[Anon]

I'm having a problem getting the following code to work properly.

There's a few things that are causing problems. One, I am trying to emulate linked lists from C in PHP because I want to be able to handle as many descriptors as I want. I don't think that is working right.

Second, I want to be able to handle multiple incoming persistent connections at once. I know how to do all this using C, yet I'm having a very difficult time getting this server script to work properly.

<?
// Turn on detailed error reporting.
error_reporting (E_ALL);

// Allow the script to hang around waiting for connections.
set_time_limit (0);

// Define some constants and global variables.

define("DAEMON_ADDRESS", "127.0.0.1");
define("DAEMON_PORT", 4001);
define("_LISTEN_BACKLOG", 20);

define("_MAX_CONNECTIONS", 25);

class DESCRIPTOR {
var $nextObj = null;
var $descriptor = -1;
var $inBuf = "";
var $outBuf = "";

function DESCRIPTOR($desc) {
	$this->descriptor = $desc;
	return;
}

function setInBuf($inBuf) {
	$this->inBuf = $inBuf;
	return;
}

function getInBuf() {
	return $this->inBuf;
}

function appendInBuf($buf) {
	$this->inBuf = $this->inBuf . $buf;
	return;
}

function setOutBuf($outBuf) {
	$this->outBuf = $outBuf;
	return;
}

function appendOutBuf($buf) {
	$this->outBuf = $this->outBuf . $buf;
	return;
}

function clearOutBuf() {
	$this->outBuf = "";
	return;
}

function clearInBuf() {
	$this->inBuf = "";
	return;
}

function getOutBuf() {
	return $this->outBuf;
}

function close() {
	$this->inBuf = "";
	$this->outBuf = "";
	close($this->descriptor);
	return;
}

function readDescriptor() {
	echo("Reading from descriptor " . $this->descriptor . ".\n");

	$nRead = read($this->descriptor, $buf, 2048);

	if ($nRead > 0) {
		$this->appendInBuf($buf);
	} else if ($nRead == 0) {
		echo("read(): EOF encountered on read");
		return false;
	} else {
		echo "read() failed for descriptor " . $this->descriptor . ": reason: " . strerror($nRead) . "\n";
		return false;
	}

    return true;
}

function readInBuf() {
	echo("Reading InBuf\n");

	$argument = trim($this->getInBuf());

	if ($argument == "") {
		return false;
	}
	echo("ReadInBuf: $argument\n");
	return true;
}

function processOutput() {
	echo("Processing Output\n");

	if ($this->writeDescriptor($this->descriptor, $this->getOutBuf()) == false) {
		return false;
	}

	return true;
}

function writeDescriptor($buf) {
	echo("Low level writing to descriptor\n");

	if (write($this->descriptor, $buf, strlen($buf)) == false) {
		return false;
	}

	return true;
}

}

function remove_from_list($list, $obj) {
if ($list == $obj) {
$list = $obj->nextObj;
} else {
$prev = null;

	for ($prev = $list; $prev != 0; $prev = $prev->nextObj) {
		if ($prev->nextObj == $obj) {
			$prev->nextObj = $obj->nextObj;
			break;
		}
	}

	if ($prev == 0) {
		echo("Remove_from_list: object not found in list.");
		return;
	}
}

}

function interpret($desc, $argument) {
if ($argument == "shutdown") {
$bMainLoop = false;
}

return;

}

function init_descriptor($descriptor, $descriptor_list) {
echo("Initializing incoming descriptor " . $descriptor . ".\n");
$desc = new DESCRIPTOR($descriptor);

if ($descriptor_list == null) {
	$descriptor_list = $desc;
} else {
	$desc->nextObj = $descriptor_list;
	$descriptor_list = $desc;
}

$desc->writeDescriptor("CONNECT OK\n");

return $desc;

}

function free_descriptor($desc) {
unset($desc);
return;
}

$descriptor_list = null;

// Open the socket
if (($ioSocket = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
die("socket() failed: reason: " . strerror ($ioSocket) . "\n");
}

if (($ret = setsockopt($ioSocket, SOL_SOCKET, SO_REUSEADDR, 1)) < 0) {
die("setsockopt() failed: reason: " . strerror ($ioSocket) . "\n");
}

if (($ret = set_nonblock($ioSocket)) < 0) {
die("set_nonblock() failed: reason: " . strerror ($ioSocket) . "\n");
}

// Bind the open socket to an address and port
if (($ret = bind ($ioSocket, DAEMON_ADDRESS, DAEMON_PORT)) < 0) {
die("bind() failed: reason: " . strerror ($ret) . "\n");
}

// Enable the socket to listen for connections
if (($ret = listen ($ioSocket, _LISTEN_BACKLOG)) < 0) {
die("listen() failed: reason: " . strerror ($ret) . "\n");
}

/
Run the main loop -
Checks for connections, initializes new descriptors, reads input from all
open descriptors, processes input, and returns output, then starts over.
/

$bMainLoop = true;

do {
if (($descriptor = accept_connect($ioSocket)) > 0) {
init_descriptor($descriptor, $descriptor_list);
}

for ($desc = $descriptor_list; $desc != null; $desc = $desc_next) {
	$desc_next = $desc->nextObj;

	echo("loop 1\n");
	if ($desc->readDescriptor() == false) {
		remove_from_list($descriptor_list, $desc);
		free_descriptor($desc);
		continue;
	}

	if ($desc->readInBuf() == true) {
	    interpret($desc, $desc->getInBuf());
	}

	$desc->clearInBuf();
}

for ($desc = $descriptor_list; $desc != null; $desc = $desc_next) {
	$desc_next = $desc->nextObj;

	echo("loop 2\n");
	if ($desc->processOutput() == false) {
		remove_from_list($descriptor_list, $desc);
		free_descriptor($desc);
		continue;
	}

	$desc->clearOutBuf();
}

// Sleep for a bit so we don't take up too much CPU.
usleep(100000);

} while ($bMainLoop == true);

close($ioSocket);
?>

[Anon]

I think you need to be a bit more specific about the problem than just saying
"it doesn't work"

But perhaps more important, why are you doing this in PHP if you can do it in C?
PHP is a scripting language, meant to drive webpages...

[Anon]

Well, as an example, I run this script and connect to it - once the first connection happens it just sits there.. it doesn't go through the descriptor loop or do anything beyond with that descriptor beyond that point. I can connect again while keeping the first connection open and the same thing happens. I don't think I did the linked lists right as they don't seem to be working.

I'm writing it in PHP instead of C because the project I am working on is a prototype and we wanted to handle these segments in PHP, for various reasons (easier to port, add things to, lots of built in web tools which is what many other scripts are handling). Since this is just a prototype it seemed like it would be easier to write/tweak in PHP than C.

Xander

[[deleted]]

You may have a problem with the "read" function.
You specify it should read 2048 bytes, but you never scheck to see if there are any bytes left to read on the socket.
The aptly named function "socket_status()" can be used to see what the socket's status is.

[Anon]

Due to some peculiarity (e.g., bug) in PHP, the socket functions don't seem to work properly with any of the more high level functions like fsockopen and socket_get_status (there is no socket_status() function, at least not in the current PHP version)... when I run a script that calls these functions on a descriptor that has been created using the socket function, it gives me: "Warning</b>: Supplied argument is not a valid File-Handle resource".