When I start my local ipfs node with ipfs daemon, in the cmd I get this:
Gateway (readonly) sever listening on /ip4/127.0.0.1/tcp/8080
With this, I can say 127.0.0.1:8080/ipfs/CID and read files from IPFS.
In my Node.js app, when I run ipfs.create(), in the console I get logs about swarms, but not about a readonly gateway server. I have found out that the ipfs.create() function has an option Gateway that on default is set to /ip4/127.0.0.1/tcp/9090. But when I run my node and keep my app running, when I try to retrieve something with 127.0.0.1:9090/ipfs/CID, I get an ERR_CONNECTION_REFUSED. Why is that? While the app is running, I scanned my ports and nothing was attached to 9090.
I have found the answer. Yes, js-ipfs has a readonly gateway server, but it's not starting implicitly togheter with the node, you have to use ipfs-http-gateway package. The package doesn't really have good instructions, but here is how you do it. You import HttpGateway class from the package and give your ipfs instance to it as a constructor, then you call .start() from the HttpGateway instance. The .start() will take the config options from your ipfs instance, and will search for Adresses -> Gateway options that defaults to /ip4/127.0.0.1/tcp/9090 and start the gateway to that port. You can read the code from the package where the HttpGateway class is written, and you'll figure it all out.