In running through the tutorial, I did the following:
arc> (defop hello req (pr "hello world"))
#<procedure: gs1709>
arc> (asv)
ready to serve port 8080
^Z
[1]+ Stopped ./goarc
mint@mint ~/bin $ ./goarc
Use (quit) to quit, (tl) to return here after an
interrupt.
Then I wanted to try some more, and it seems that the port is still in use.