Techstaff are not experts on VS Code or its proprietary SSH extension, but I can guess what's happening based on what we've seen with other students.
This can occur if you've used VS Code and logged into more than one of our login servers.
linux.cs.uchicago.edu is actually a collection of several servers, so when you access that address your computer will pick a login server to use.
Using nslookup, dig, host, or another DNS lookup tool, you can see that
linux.cs.uchicago.edu expands to
linux2.cs.uchicago.edu, and other servers up to
In this case, VS Code has started its server process for you on two of our login servers concurrently: linux1 and linux2. This causes it to show the error message you're seeing. Additionally, this can often
result in the directory
~/.vscode-server in your home directory on the server becoming corrupted in some way. Since VS Code will automatically recreate that directory when you reconnect, it's safe to delete it.
To try to clear this up for you, I've stopped the VS Code server process which was running on those two servers and removed the
~/.vscode-server folder from your home directory.
To help ensure that this doesn't happen again, you might consider configuring VS Code to connect to one login server in particular instead of the group. That will ensure that you always reconnect to the same system you used previously, which means it'll be less likely that you'll accidentally end up with two instances of the server process running concurrently.