While installing vCommander®, you receive the error message The specified main port is already in use on the Port Configuration page of the installation wizard.

This means that the installer has tried to open the port and failed, typically because another application is already running on the port. Most frequently this will be Internet Information Services (IIS) running a web server on port 443, but other applications could also be bound to the port.

To see what applications are currently listening on a port, open a command prompt and issue the command:

netstat -aob

As you can see in the image above, tomcat7.exe is running on TCP port 443. When an existing application is using the port your options are to change the port from 443 to another unoccupied port (note  users will have to include the port in the URL when accessing vCommander), or to install vCommander on another server dedicated to it.

Alternatively, you can use a graphical tool such as TCPView.

If you are unable to locate a service using the port, it’s possible that the host name of the application is actually resolving to the wrong address. When this occurs, the installer is checking the port for the wrong machine, where a service may be running on the port as the installer reports. To confirm this, you can manually check the DNS records on the Domain Controller and hosts file on the vCommander application server, or issue the following from a command prompt on the application server:

nslookup hostname

Replacing hostname with the name of the vCommander application server. Then, issue the command ping -a using the IP address returned for the hostname from the first command.

ping -a xxx.xxx.xxx.xxx

If you discover a mismatch, there is an issue with name resolution causing the installer to check the ports in an incorrect location.