UDP broadcast send from PHP and receive in C#

I'm trying to send a broadcast UDP message to a C# application. I have tried the following code to send the message. Which I found on the php.net website as a comment to the socket_sendto manual page.

<?php 
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); 
socket_set_option($sock, SOL_SOCKET, SO_BROADCAST, 1); 
socket_sendto($sock, $broadcast_string, strlen($broadcast_string), 0, '255.255.255.255', $port); 
?>

This doesn't work for me, maybe it's my network.

But it does work if I replace the broadcast IP '255.255.255.255' to my specific IP e.g. '192.168.1.128'. I can see this message coming in with Wireshark, while I can't see this using the above code. This leads me to believe there is something wrong with the PHP side of the code. I really want to use broadcasting or some kind of multicasting for my program, so I'm a bit stuck at the moment ;)

I use the following on the (C#) receiving end (for testing):

UdpClient subscriber = new UdpClient(15000);

IPEndPoint ep = new IPEndPoint(IPAddress.Any, 15000); ;

byte开发者_StackOverflow[] pdata = subscriber.Receive(ref ep);
string data = Encoding.ASCII.GetString(pdata);
MessageBox.Show(data);
subscriber.Close();

Any idea what could be the cause of this?

Try specifying the MSG_DONTROUTE flag in your script. Taking inspiration from this CodeGuru post, if this isn't specified the routers make the decision on whether or not to broadcast your message.

socket_sendto($sock, $broadcast_string, strlen($broadcast_string), MSG_DONTROUTE, '255.255.255.255', $port);

255.255.255.255 is a "limited" broadcast whereas your 192.168.1.255 is a "directed" broadcast. Limited in simple terms means that it is only send within the LAN. LAN as defined by directly connected hosts, i.e. with no router in between. Routers--with a few exceptions--do not pass a limited broadcast but a directed broadcast.

Now, with your initial problem and question, I can only guess that you are sending your broadcast across a router.