Allow specifying incoming torrent port

[nochso]

Adds a new flag -torrent-port to specify the listening port for torrent connections.

However having both port and torrent-port might be confusing. How about http-port and torrent-port or http and torrent?

As of now:

Usage of ./go-peerflix:
  -player string
        Open the stream with a video player (VLC, MPV, MPlayer)
  -port int
        Port to stream the video on (default 8080)
  -seed
        Seed after finished downloading
  -tcp
        Allow connections via TCP (default true)
  -torrent-port int
        Port to listen for incoming torrent connections (default 6882)

[Sioro-Neoku]

I feel a bit reluctant, as I'm not sure many people need this (and the client.NewClient() method is just getting increasingly bloated).

One thing I'd definitely change is using the default torrent port (6882), as for many users this port is probably blocked (or monitored?).
Many clients randomize their torrent port. If we'd do the same, it is a feature I'm happy to merge.

[nochso]

I agree on randomizing by default / if left empty. Probably in the range of 1025-10000 to avoid <=1024 root related issues.

Otherwise, to me it makes sense. You're most likely uploading anyway, so why not help other peers which are NATed or otherwise firewalled? In my experience download speeds increase too.

Not sure what to do about client.NewClient(). Maybe set the listening port after instantiation?

[Sioro-Neoku]

An idiomatic go practice is to replace a long list of arguments with a config structure.

Something like

type ClientConfig struct {
  torrentPath string
  port int
  torrentPort int
  seed bool
  tcp bool
}

A method on the structure could fill in the default values.

[nochso]

Turns out port randomization has its drawbacks: http://dev.deluge-torrent.org/ticket/2133

How about keeping the current default by anacrolix/torrent and allowing to override it? Alternatively, one could generate a random port based on something that is host/machine specific and doesn't change.

[nochso]

Ok, I've added ClientConfig with a method for instantiating with defaults.

The flags are bound to the config which is then passed to the client after flag parsing.

[Sioro-Neoku]

Looks pretty good now!

One thing I'd change is to make the fields of the ClientConfig structure public:

type ClientConfig struct {
    TorrentPath    string
    Port           int
    TorrentPort    int
    Seed           bool
    Tcp            bool
    MaxConnections int
}

I understand that you just copied what I wrote, so it's clearly on me =)

[nochso]

Ok :) I've amended the last commit and made the fields public.

[Sioro-Neoku]

Looks great, thank you!