Add announce_port support

[0xThiebaut]

The announce_port setting permits to overwrite the port passed along to trackers as the &port= parameter. If left as the default, the listening port is used. This setting is only meant for very special cases where a seed's listening port differs from the effectively exposed port (e.g., through external NAT-PMP). See arvidn/libtorrent#7771 for an example use-case.

This PR adds the relevant setting alongside the existing announce_ip setting.

The setting subsequently modifies the announced port (&port=1234):

127.0.0.1 - - [27/Oct/2024 09:44:16] "GET /announce?info_hash=%a7%801%f7%3b%a1k%3a%8e%b6%84%dd%cfyw%f1%f3%b8m!&peer_id=-qB5100-YwWihiQ4KGdM&port=1234&uploaded=0&downloaded=0&left=0&corrupt=0&key=CEDD0BC7&event=started&numwant=200&compact=1&no_peer_id=1&supportcrypto=1&redundant=0&ip=1.2.3.4 HTTP/1.1" 404 -

[0xThiebaut]

On a side-note, the requires restart statement was copied over from the similar announce_ip setting; I'm however doubting whether this is an accurate statement for both.

[github-actions]

This PR is stale because it has been 60 days with no activity. This PR will be automatically closed within 7 days if there is no further activity.

[github-actions]

This PR was closed because it has been stalled for some time with no activity.

[Neustradamus]

@0xThiebaut: What is the situation of your PR?

[0xThiebaut]

@Neustradamus this PR was closed due to inactivity as completing the PR required the upstream arvidn/libtorrent#7771 change to reach a release. libtorrent:v2.0.11 was released 3 days ago so I will re-open the PR this weekend.

[xavier2k6]

@0xThiebaut FYI - libtorrent 2.0.11 isn't available in our CI yet, however #22217 is open/approved & should be merged within the next day.

[0xThiebaut]

Thanks for the heads-up @xavier2k6 , any chance you have the permissions to reopen this PR? It was closed as stale and I'd prefer re-opening it to maintain the history instead of filing a new one.

[xavier2k6]

Re-opened

[0xThiebaut]

Pending #22217

[xavier2k6]

Pending #22217

Merged now.

[xavier2k6]

@0xThiebaut It mat be worthwhile to re-base.

[0xThiebaut]

@0xThiebaut It mat be worthwhile to re-base.

Rebased.