Add support for adding peers by IP:port

[Avamander]

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Summary

Would it be possible to add a small "+" to "Torrent details"->"Peers" that allows adding a new peer by IP:port? As far as I understand rtorrent supports it via d.add_peer=host[:port] but it would be nice to have access to the feature via UI.

[noraj]

Hi @Avamander Have you a use case for that? I can't image a way you need to manually add peers right now because if a peer is available the tracker will know it and your bittorrent client will add it to the list of connected peers if it match to your peers limit policy.

Update : filling this part of the template could have helped:

## Context
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[Avamander]

Have you a use case for that?

Yes. For example when no trackers can be contacted (or should be contacted) and when I know there's a specific host I can get the files from. Say two PCs on the same network, one has the whole file, other doesn't, adding the LAN IP would allow downloading from that first PC.

[noraj]

Right, DHT only works if you have an Internet connection, and the feature you ask for is far lighter than deploying it's own tracker on a LAN.

[SanPilot]

This shouldn't be too difficult. rtorrent supports d.add_peer=host[:port] syntax since 0.8.4, so we can add button/ui in the peers tab of torrent details and a corresponding API endpoint in the backend.