What does “The port 8888 is already in use, trying another port.” mean for Jupyter?
When you’re starting up a Jupyter server, you might get a message about “the port already being in use.” The server will work, the notebooks will open, but it’s still confusing! It might look something like one of these:
[I 07:28:23.107 NotebookApp] The port 8888 is already in use, trying another port.
[I 07:28:23.107 NotebookApp] The port 8889 is already in use, trying another port.
[I 07:28:23.107 NotebookApp] The port 8890 is already in use, trying another port.This happens when you start a new Jupyter server after you’re already running a Jupyter server. Maybe you minimized the Terminal window, forgot about it, and started a brand-new one.
A ‘port’ is basically an address on your computer. By default, Jupyter uses port 8888 to let you talk to it (you can see this in the URL when you’re looking at a notebook: localhost:8888). If you’re already running a server, it will try 8889, then 8890, then 8891 and so on, until it finds an opening.
While this isn’t really a problem or error, you probably don’t need to be running multiple Jupyter servers! Before starting a new one, always check at http://localhost:8888 to see if a server is already running.