Port checking from php

I'm trying to connect to gmail pop server from a phplist installation and it fails, but i'm not sure whether my webhost opened port 995 or not. They say they have opened it, but i'm in doubt. Is there a way i can check it from a php script? They are running php 5.2.0 on a windows server, though i'm not sure what OS is that. phpinfo() says "Windows NT DEDI514 5.2 build 3790"

Solution

You can put code in a php script to open a connection to a specific hostname (or IP address) and port. If you know the expected response, you should be able to tell if you are getting a connection. If you get something like "Connection refused", then either you are being blocked, or the destination host is not accepting connections on that port.

This example uses IP address 192.0.2.0 and port 995. Replace these with whatever you want to test.

<?php
    echo "\nOpening connection\n\n";

    $fp = fsockopen("192.0.2.0", 995, $errno, $errstr);
    if (!$fp) {
        echo "ERROR: $errno - $errstr\n";
    } else {
        echo fread($fp, 1024);
        fclose($fp);
    }
?>

You can also send data to the server using

fwrite($fp, "blah blah blah\r\n");

There is more information about fsockopen here.