[javascript] How to find out the server IP address (using JavaScript) that the browser is connected to?

Fairly certain this cannot be done. However you could use your preferred server-side language to print the server's IP to the client, and then use it however you like. For example, in PHP:

<script type="text/javascript">
    var ip = "<?php echo $_SERVER['SERVER_ADDR']; ?>";
    alert(ip);
</script>

This depends on your server's security setup though - some may block this.