add support to bind to port 0 in emrun

[arsnyder16]

Allowing port 0 binding will find an available port automatically.

This is useful in situations where you want run emrun multiple times with something like GNU parallel

Example output

# ./emrun --verbose --no_browser a
Web server root directory: /root/arsnyder16-emscripten
Starting web server: http://0.0.0.0:6931/
Now listening at http://0.0.0.0:6931/
Entering web server loop.
^CClosed web server.
emrun quitting with process exit code None
# ./emrun --verbose --no_browser --port 0 a
Web server root directory: /root/arsnyder16-emscripten
Starting web server: http://0.0.0.0:0/
Now listening at http://0.0.0.0:41261/
Entering web server loop.
^CClosed web server.
emrun quitting with process exit code None

[kripken]

maybe add a comment here? otherwise it is a little odd to see port passed in and then read back.

[arsnyder16]

Good call. Added.

[kripken]

Thanks!

[kripken]

I wonder if we could use this to parallelize our browser test suite here... (edit: not this specifically, as we don't use emrun for most tests, but we could spawn in parallel using port 0)

[arsnyder16]

I wonder if we could use this to parallelize our browser test suite here... (edit: not this specifically, as we don't use emrun for most tests, but we could spawn in parallel using port 0)

This will certainly open the door, our native tests are all with gtest so we are able to leverage the sharding it can do.

[sbc100]

I wonder if we could use this to parallelize our browser test suite here... (edit: not this specifically, as we don't use emrun for most tests, but we could spawn in parallel using port 0)

I don't think the browser test suite uses emrun. I'm also not sure lack of port numbers would be blocking factor there.