Calibre is one of the most popular free ebook reader, converter, editor. It offers excellent support for converting books to different formats and sending them to other devices easily. For example, iOS users can use it to convert ePub books for iPhone iPad for free, then send Calibre books to iPhone iPad wirelessly using its Content Server utility. Before the transfer however, you will need to turn on the Content Server on computer first so other devices and computers can access your Calibre libraries and read books directly in a web browser. To do that, click the Connect/share button and choose Start Content server. If no error message pops up, you should get the content server address in the same place you start the server. Click the Connect/share button again. Instead of the Start Content server, you should see a Stop Content server action with an IP address and port number.
You can use this IP address and port number to connect to Calibre library from other computers and devices connected to the same network. Sometimes however the content server may fail to start and through an error: No socket could be created. Errno 10013.
If you run into this problem when trying to start Calibre server, you can try to change a different port number for the Content Server or figure out if the default port number is used by another program and kill the program before starting the Content Server in Calibre.
Changing Calibre Content Server Port Number
To change the default server port, click the Preferences button and choose “Sharing over the net” in the pop-up window. In the “The port on which to listen for connections” box, enter a new port number. You can change the port number from 8080 to another, say 8000, 8081, etc. Click Apply button at the bottom-right corner to apply the change. Then restart Calibre Content Server.
Release port 8080 before starting Calibre server on Windows computer
On a Windows 10 PC, you can press Windows+R on your keyboard to open the Run dialog. Type in cmd and press OK to quickly launch the Command Prompt in Windows 10. In the Command Prompt, type in “netstat -ano” without the quotes, and press Enter on the keyboard to see a list of ports and find out which program is using port 8080. Find the string that contains the port 8080 and write down its PID, the number can be found at the end of this string. A PID is a unique number that identifies each of the running processes on PC. Or you can simply execute netstat -aon|findstr “8080” in the Command Line to see which program is using port 8080 in an easier way. Again keep a record of the PID number.
Now we need to use the PID to find out the running process from Windows Task Manager. There are several ways you can access Task Manager in Windows 10 and earlier versions. Right click the Windows menu, choose to open Task Manager on Windows 10 computer; Or just right-click on the taskbar and then select Task Manager. The Processes tab opens automatically in Task Manager. It however doesn’t show the PID. Switch to the Details tab in Windows Task Manager instead. You will see many different columns here including Name, PID, Status, User name, CPU, Memory and so on. Click PID in the PID column to sort all processes by PID number so you can quickly find the PID that we have found in the Command Prompt above. Click the its name or the PID, then hit the End Task button at the bottom right corner to kill the process or close down the application which is currently using port 8080.
Finally the port 8080 is free. We can go to start the Calibre server and transfer books to other devices now. You should now access Calibre libraries using any web browser on your computer.
If you have trouble connecting to Calibre server from another device or computer in your local network, double check the Windows Firewall on the current PC as it may prevent the connection to port 8080. You can follow this step-by-step guide to allow network access to Calibre server on port 8080 in Windows Firewall. Alternatively use third-party file transfer solutions. For instance, you can transfer books and other files between computer and mobiles using ShareIt, a free, cross-platform file transfer. Windows has the built-in file transfer over SMB which you also consider. Check out this guide to share files between PC and iPhone, iPad via Windows File Sharing for more details.