Check the Firewall(s)
Description
Firewalls control network access to your server in order to provide a layer of security from malicious attacks. In the process of blocking undesirable access though, they can also block access to your server that you want to allow. If your Application Server appears to start correctly but clients cannot connect to it, it is quite likely that a firewall is blocking network access to your Application Server.
Discussion
Most versions of Windows include Windows Firewall, a built-in firewall to control what incoming connections are allowed, and also which programs may accept incoming connections and initiate outgoing connections. It is important to be aware that Windows Firewall exceptions (connections which will be allowed) can be set by the TCP port number, but also by the specific application. This means that it is possible that you may have previously configured Windows Firewall to allow an older version of the Application Server to function properly, but a new version does not work as expected because it is a totally different application with respect to Windows Firewall. In this case, you need to add a new exception to the firewall rules.
In addition to Windows Firewall, many common security software packages, such as McAfee Total Protection and Norton Internet Security, include a firewall for additional protection. If you have software such as this installed, you should review its accompanying documentation and ensure that it is not blocking access to your Application Server.
In addition to software-based firewalls discussed above, many networks also use hardware firewalls to restrict network access. These are dedicated devices that provide similar access control to that of a software firewall, but across an entire network instead of on a single PC. You should consult your network administrator to find out if there is a hardware firewall in use and if it may need to be specially configured for your Application Server.