Json RCP access fails through Docker container

[chevdor]

While http and ws connections work with polkadot running locally, the same requests fail with a Docker container despite the ports being open.

tested with:

docker run --rm -it -p 9944:9944 -p 30333:30333 -p 9933:9933 -v ~/Library/Application\ Support/Polkadot/:/data chevdor/polkadot polkadot

curl -H "Content-Type: Application/json" -d "{}" http://localhost:9933

[tomusdrw]

Are the ports exposed in Docker? What error are you getting?

[chevdor]

Using polkadot sending an (invalid) request such as curl -H "Content-Type: Application/json" -d "{}" http://localhost:9933, I do get an answer: {"jsonrpc":"2.0","error":{"code":-32600,"message":"Invalid request"},"id":null}

Using docker run --rm -it -p 9944:9944 -p 30333:30333 -p 9933:9933 -v ~/Library/Application\ Support/Polkadot/:/data chevdor/polkadot polkadot (you see with -p 9933:9933 that the port is open and exposed) and the same curl request, I get:

curl: (52) Empty reply from server

I did nmapin both cases and the port is open:

$ nmap localhost -p 9933
Starting Nmap 7.70 ( https://nmap.org ) at 2018-07-30 11:21 CEST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00034s latency).
Other addresses for localhost (not scanned): ::1

PORT     STATE SERVICE
9933/tcp open  unknown

[chevdor]

The initial issue I had btw was to connect the UI to polkadot running in the container and the web socket connection fails. Since I see a similar issue with http and this is easier to test and debug, I focus on the http issue first but I suspect this is the same story for both.

[tomaka]

I would guess that polkadot only listens on 127.0.0.1 by default, so it would only accept connections from inside the container.

[chevdor]

Indeed @tomaka. But mapping the ports as as I did should work.
It works for nginx for instance: docker run -it --rm -p 82:80 nginx will show you a nice welcome from nginx at http://localhost:82

Should not polkadot listen on all interfaces => 0.0.0.0 ?

[chevdor]

Note to self: test a change at https://github.com/paritytech/polkadot/blob/master/substrate/cli/src/lib.rs#L296 from 127.0.0.1 to 0.0.0.0

[chevdor]

See #495