The error message "Agent installation in the target host is failed since 42005 port is already in use" is encountered during agent installation on the target host.

This error occurs when the VIS Agent Port (port 42005) is already in use on the target machine by another application.

1. Check Port Usage:

1. Open the command prompt by going to 'Run' and executing "cmd."
2. Run the following command
3. Netstat -ano | find "42005"
   
4. If the port is in a listening state, it will display "Listening" as the result.
   

2. Change Port for Other Application:

1. If you still need to add the target host, change the port used by the application that occupies port 42005.
2. After changing the port, attempt to re-add the target host from the BDR server
   

3. Customizing Port (For v5.5.0 and Later):

1. Starting from v5.5.0, you can customize the port by following these steps on the BDRSuite Backup Server machine:
   

1. Open the "config.inc" file located at:
   

   - Windows: C:\Program Files\Vembu\VembuBDR\htmlgui\conf\

   - Linux: /home/vembubdr/Vembu/VembuBDR/sgchroot/htmlgui/conf/

1.  Search for the `$ADD_HOST_PORT_ENABLE` tag and change its value from 0 to 1.
   
2.  For v5.3, add the following line before the last "?>" line:
   

       $ADD_HOST_PORT_ENABLE = 1;

1.  Save and close the file
   

4. Open "services.msc" and restart the "BDRSuite WebServer" and "BDRSuite Backup Server Virtual Physical Workloads" services.
   
5. Log in to the WebConsole and attempt to add the host with the custom port from "Data Sources" -> "Add Microsoft HyperV," "Add Microsoft Windows," or "Add Linux path."