Merge #14120: Notes about control port and read access to cookie

fb97437 added note that control port must be enabled and how to do that in torrc config file (Jordan Baczuk)

Pull request description:

  Reopened from #13681 because pushes made it unable to reopen.

Tree-SHA512: 34eac14308aef70963b630173cd93916201553d5323ab2de3517d4a78604ae5a7cf8691a314c0af00fe36f0ef19b94a4c371d2e7aa1229d9c603d36c51b115fb

Author: laanwj

doc/tor.md

@@ -93,7 +93,7 @@ API, to create and destroy 'ephemeral' hidden services programmatically.
 Bitcoin Core has been updated to make use of this.
 
 This means that if Tor is running (and proper authentication has been configured),
-Bitcoin Core automatically creates a hidden service to listen on. This will positively 
+Bitcoin Core automatically creates a hidden service to listen on. This will positively
 affect the number of available .onion nodes.
 
 This new feature is enabled by default if Bitcoin Core is listening (`-listen`), and
@@ -102,8 +102,9 @@ and, if not disabled, configured using the `-torcontrol` and `-torpassword` sett
 To show verbose debugging information, pass `-debug=tor`.
 
 Connecting to Tor's control socket API requires one of two authentication methods to be
-configured. For cookie authentication the user running bitcoind must have write access
-to the `CookieAuthFile` specified in Tor configuration. In some cases, this is
+configured. It also requires the control socket to be enabled, e.g. put `ControlPort 9051`
+in `torrc` config file. For cookie authentication the user running bitcoind must have read
+access to the `CookieAuthFile` specified in Tor configuration. In some cases this is
 preconfigured and the creation of a hidden service is automatic. If permission problems
 are seen with `-debug=tor` they can be resolved by adding both the user running Tor and
 the user running bitcoind to the same group and setting permissions appropriately. On