When you click on the Enter Chat button, your web browser downloads a program called a "Java applet". In order to run this applet, which provides your interface to the chat server, you must have a "Java Virtual Machine" (JVM) installed and activated in your browser.
If the chat applet (that is, the chat window containing the buttons and text area described throughout this chapter) doesn't start at all, the reason may be that Java is not enabled on your web browser. For Internet Explorer, try clicking on Tools from the menu, then Internet Options, then click on the "Advanced" tab and scroll down to look for a checkbox to turn Java on. For Netscape and related browsers, the options can usually be found by clicking on Edit from the menu, then Preferences, then Advanced.
Unfortunately, things may not be as simple as enabling Java. If you get an empty gray screen instead of the chat program when you click the Enter Chat button, you may have an incompatible version of Java installed. This annoying problem deserves the following digression.
Java is a programming language developed by Sun Microsystems. The initial promise of Java was that programmers would be able to write programs, like Manhattan's chat client, that would run on any computer (for example any version of Windows or Macintosh) as long as that computer had a piece of software called a "Java Virtual Machine" installed.
At some point, Sun licensed Java technology to Microsoft. Microsoft soon created their own Java Virtual Machine, called the "Microsoft VM", which was not fully compatible with Sun's version. The unfortunate effect of this is that it is no longer true that a user can run any Java program, as long as they had a Java VM installed. Now, some Java programs will work only if you have Microsoft's VM, some will work only if you have Sun's VM, and some will work with both.
Sun Microsystems sued Microsoft over this issue, charging that Microsoft violated their licensing agreement by creating an incompatible VM. Microsoft responded by first shipping some versions of Windows XP with NO JAVA SUPPORT at all. If you have one of these early versions of Windows XP, and you did not take the extra steps to download the Microsoft VM or the Sun VM and install it on your computer, you cannot enter the chat program at all. Some point later, Microsoft again started including their (incompatible) Microsoft VM in Windows XP.
The bottom line is that if you have trouble using Manhattan's chat, especially if you get a blank gray screen at least some of the time you enter chat, you should download and install Sun's Java Virtual Machine. At the time of this writing, an automated install is available at http://java.sun.com/getjava . If that address no longer works, look for the latest version of the Sun Java Virtual Machine at http://java.sun.com or perhaps http://www.sun.com
The second issue you may have with chat involves firewalls. Networking professionals at companies and schools use firewalls to control the type of traffic that moves through their network to and from the Internet. This is generally done to protect the data and servers owned by that business or school from attacks by "crackers" who maliciously try to gain access to the network. Sometimes a company may use a firewall to prevent its employees from doing certain things on the Internet. A company might allow its employees to view web pages and send e-mail, but it may have configured its firewall to prevent questionable (in light of the goals of their business) practices like chat.
If you or a student can't access chat from certain locations (e.g. it works from campus, but not from the office), there's a good chance that a firewall setting is preventing the chat traffic from passing. The person responsible for the network blocking the traffic should be told they need to open up a particular "port" to enable chat sessions. Generally Manhattan's chat runs on port 6666, but this may have been changed by the person who installed Manhattan. Your Manhattan system administrator should be able to tell you which port Manhattan's chat runs on.