Question

I’m trying to make a simple listener on port 8195. When I try the following code block in PHP CLI conditions, it only shows ‘Test’ once, then hangs. If I delete the file ‘votifier.run’, the file designed to be the on/off switch, it still continues to hang. It never shows ‘Client connected’.

Furthermore, if I try to connect to the host via Telnet on port 8195 while the script is running, I simply get a connection failed message. It’s like it’s looking for one connection and just not giving up.

// Set the IP and port to listen to
$address = 'localhost';
$port = 8195;

// Create a TCP Stream socket
$sock = socket_create(AF_INET, SOCK_STREAM, 0);
// Bind the socket to an address/port
socket_bind($sock, $address, $port);
// Start listening for connections
socket_listen($sock);

// Loop continuously
while ( file_exists('votifier.run') ) {
    echo 'Test';
    $client = socket_accept($sock);
    if( $client ) {
            echo 'Client connected';
            // Don't hang on slow connections
            socket_set_timeout($client, 5);

            // Send them our version
            socket_write("VOTIFIER MCWEBLINK\n");

            // Read the 256 byte block
            $block = socket_read($client, 256);
            ...

The answer:
socket_accept() will usually hang until a connection is made. If a connection attempt was made, the script would continue, but because the socket was being created on localhost, it would only accept connections to it from localhost.

The fix is to use your external IP rather than ‘localhost’ or ‘127.0.0.1’. Then you can Telnet to it.

Answer 1

I’m just guessing here, but could it be that the address you are trying to bind to should not be a hostname?

If the socket is of the AF_INET family, the address is an IP in dotted-quad notation (e.g. 127.0.0.1).

EDIT

Ok, I’ve taken your script and tried to reproduce your error but couldn’t. There are a couple of flaws in it but none that would cause a telnet client’s connection attempt to fail.

Since none of the aforementioned applies, let’s go thru the checklist one by one:

• sockets module loaded/compiled
• localhost does resolve to 127.0.0.1
• the port isn’t taken by any other application running
• there’s no rule of any sort of firewall that would prevent communication between the telnet client and your server
• the machine which you connect from is allowed to connect to the server host (try the same host if it isn’t)
• the file that’s being checked in the while-loop does exist
• you are sure that there isn’t another fatal error within your script that would prevent the snippet you posted from running

These are all the possible error sources I can think of, atm. Try fixing up the minor flaws first, then go thru the checklist.

if( $client ) {
    echo 'Client connected';
    // Don't hang on slow connections
    socket_set_option(
        $client,
        SOL_SOCKET,
        SO_RCVTIMEO | SO_SNDTIMEO,
        array('sec' => 5, 'usec' => 0)
    );

    // Send them our version
    socket_write($client, "VOTIFIER MCWEBLINK\n");
                 ^^^^^^^

    // Read the 256 byte block
    $block = socket_read($client, 256);