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I’m trying to create a custom block, but when I run:

block run

I get:

Error: listen EACCES: permission denied 0.0.0.0:9001

I’ve checked and there’s a system task already listening to this port, so I’m not able to just kill it.
Is there a way to change the listening port so that I can make this work?

Hi @wbaleroni

Sorry you’ve been running into issues! I would’ve expected the CLI to detect the collision and prompt you for another port, but I think you should be able to work around this by another means: the default port can be configured using the default-port argument, e.g.

block run --default-port 9002

Hope this helps!


Hi @wbaleroni

Sorry you’ve been running into issues! I would’ve expected the CLI to detect the collision and prompt you for another port, but I think you should be able to work around this by another means: the default port can be configured using the default-port argument, e.g.

block run --default-port 9002

Hope this helps!


I had the same issue; 9001 was taken by System - thanks!


block run --port=<port number> is the correct command to change the default port number