How to determine if a PC is on line?

Leigh · 11-25-2005, 06:06 PM

I'm writing an inventory program that goes out and interrogates a PC for its hardware and software. However, before I do this I want to ensure that the PC is switched on and on line. How can I do this in PHP? I don't really want to shell out and PING the computer, I'm just hoping there's a more subtle method.

The network is all Windows, with XP Pro desktops/laptops and NT4/WK2003 servers.

Dennis Pallett · 11-27-2005, 07:42 PM

Maybe you can try something with fopen or file_exists? For example:

PHP Code:

if (file_exists('/path/to/file/on/the/other/computer') == true) {
 // computer is online
 else {
 // computer is offline (or file doesn't exist, so make sure the file does exist)
 }

Something like that maybe?

I've never had to something like this to be honest, and I don't know of any other practical way (short of using shell and ping like you mentioned).

Leigh · 11-28-2005, 08:47 PM

Well, after much digging around I discovered the fsockopen function on PHP.NET and cobbled together this little snippet of code:

PHP Code:

$isThere = @ fsockopen("10.0.0.25", 135, $errno, $errstr, 10);

                            if (!$isThere) {

                             echo "Offline";

                            } else {

                             echo "Online";

                            }

It's not a true PING as PING doesn't really use a port, but fsockopen requires a port to be specified. I used the infamous TCP port 135. The other parameters aren't required for this little snippet, but I left them there for completeness.

The other problem I had with this snippet was that if a PC is offline, I got a couple of PHP warnings that broke the display. Once again, Google to the rescue, I found that putting the "@" sign in front of the function suppressed the warnings. That was new one to me!

Dennis Pallett · 11-29-2005, 04:39 PM

Excellent way of doing it, the only downside is the need for 135 which is often blocked. But if it's only for internal use, it should be fine!

I'm going to wrap this up in a FAQ on PHPit.

Leigh · 11-30-2005, 06:45 PM

Indeed, you are right, Dennis, port 135 may be blocked for security reasons. I am using this internally so the security risk isn't that great, and I also had to choose a port that I could guarantee to be available on our Windows workstations and servers. For anyone who's interested in finding other ports that may be used try this from a command line:

netstat -an |find /i "listening"

Dennis Pallett · 12-02-2005, 09:06 PM

I've posted this as a FAQ, available at http://phpit.net/faq/determining-if-a-pc-is-online/. Thanks for the tip!

11-25-2005, 06:06 PM	#1
Leigh Junior Member Join Date: Nov 2005 Location: Ontario, Canada Posts: 10	How to determine if a PC is on line? I'm writing an inventory program that goes out and interrogates a PC for its hardware and software. However, before I do this I want to ensure that the PC is switched on and on line. How can I do this in PHP? I don't really want to shell out and PING the computer, I'm just hoping there's a more subtle method. The network is all Windows, with XP Pro desktops/laptops and NT4/WK2003 servers.

11-27-2005, 07:42 PM	#2
Dennis Pallett Administrator Join Date: Nov 2005 Posts: 258	Maybe you can try something with fopen or file_exists? For example: PHP Code: `if (file_exists('/path/to/file/on/the/other/computer') == true) { // computer is online else { // computer is offline (or file doesn't exist, so make sure the file does exist) }` Something like that maybe? I've never had to something like this to be honest, and I don't know of any other practical way (short of using shell and ping like you mentioned).

11-28-2005, 08:47 PM	#3
Leigh Junior Member Join Date: Nov 2005 Location: Ontario, Canada Posts: 10	Well, after much digging around I discovered the fsockopen function on PHP.NET and cobbled together this little snippet of code: PHP Code: `$isThere = @ fsockopen("10.0.0.25", 135, $errno, $errstr, 10); if (!$isThere) { echo "Offline"; } else { echo "Online"; }` It's not a true PING as PING doesn't really use a port, but fsockopen requires a port to be specified. I used the infamous TCP port 135. The other parameters aren't required for this little snippet, but I left them there for completeness. The other problem I had with this snippet was that if a PC is offline, I got a couple of PHP warnings that broke the display. Once again, Google to the rescue, I found that putting the "@" sign in front of the function suppressed the warnings. That was new one to me!

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11-29-2005, 04:39 PM	#4
Dennis Pallett Administrator Join Date: Nov 2005 Posts: 258	Excellent way of doing it, the only downside is the need for 135 which is often blocked. But if it's only for internal use, it should be fine! I'm going to wrap this up in a FAQ on PHPit.

11-30-2005, 06:45 PM	#5
Leigh Junior Member Join Date: Nov 2005 Location: Ontario, Canada Posts: 10	Indeed, you are right, Dennis, port 135 may be blocked for security reasons. I am using this internally so the security risk isn't that great, and I also had to choose a port that I could guarantee to be available on our Windows workstations and servers. For anyone who's interested in finding other ports that may be used try this from a command line: netstat -an \|find /i "listening"

12-02-2005, 09:06 PM	#6
Dennis Pallett Administrator Join Date: Nov 2005 Posts: 258	I've posted this as a FAQ, available at http://phpit.net/faq/determining-if-a-pc-is-online/. Thanks for the tip!