Stalled torrents

A stalled torrent is one that stops downloading partway through, or never starts at all. The status shows "stalled," "connecting to peers," or just sits at 0% with no progress.

Most of the reasons torrents stall have nothing to do with the torrent itself. They are network problems between you and the swarm. ISP throttling, NAT issues, firewall rules, and DNS failures all produce the same symptom: the download freezes.

On a Pulsed Media seedbox, torrents run on datacenter bandwidth in Finland with no ISP between the torrent client and the internet. ISP throttling, home router NAT, and local firewall problems do not exist. That is why the same torrent that stalls on a home connection downloads at full speed on a seedbox.

ISP throttling

ISPs inspect traffic using deep packet inspection (DPI) and throttle or block BitTorrent connections. Some ISPs do this openly, others deny it while shaping traffic based on protocol signatures.

Symptoms: torrents stall after a few seconds or minutes, download speed drops to near zero, but regular web browsing works fine. Speed tests show normal bandwidth. The torrent client cycles through "connecting to peers" without making progress.

Encryption in the torrent client (forced encryption in rTorrent, Deluge, or qBittorrent) helps against basic DPI. It does not help against ISPs that throttle all non-HTTP traffic or block known tracker ports.

A seedbox eliminates ISP throttling entirely. The torrent traffic stays within the datacenter network. You download files from the seedbox to your local machine over SFTP or HTTPS, which ISPs do not throttle.

No incoming connections (NAT/firewall)

BitTorrent works best when peers can connect to you directly. If your torrent client cannot accept incoming connections, it can only connect out to peers that are themselves connectable. This cuts the available swarm in half or worse.

Home routers use Network Address Translation (NAT). Without port forwarding, incoming connections are silently dropped. The torrent client shows a warning icon or "no incoming connections" but continues working in a degraded state. Torrents with few seeders become much more likely to stall because you cannot reach the seeders that are also behind NAT.

Double NAT (your router behind the ISP's router, common with CGNAT on mobile and fiber connections) makes port forwarding impossible. There is no workaround on the home side.

On a PM seedbox, the torrent client runs on a server with a public IP address. No NAT, no port forwarding, no firewall blocking torrent ports. Every peer in the swarm can connect directly.

Dead or thin swarms

If a torrent has no seeders, or all seeders are offline, the download stalls at whatever percentage was reached. The client waits for a seeder to come online.

Check the peer count in your torrent client. If it shows "0 seeds, 0 peers" or the tracker status says "0(0)" for seeds and leechers, the torrent is dead. No seedbox or configuration change can fix a swarm with no seeds.

If the swarm has seeders but they are slow, a seedbox still helps. A datacenter connection in Finland can reach peers that a throttled home connection behind NAT cannot. The 1 Gbps or 10 Gbps link also means you download your share faster when competing with other leechers for the available bandwidth.

Session corruption (rTorrent)

rTorrent stores download state in session files. If the process crashes mid-write, those files can become corrupted. Symptoms: rTorrent starts but shows torrents stuck at "Checking" forever, or previously active torrents show 0% and will not resume.

To fix corrupted session data:

Make sure rTorrent is not running (check with screen -list)
Delete the session directory contents: rm -rf ~/session/*
Restart rTorrent

This loses your torrent list. You will need to re-add the .torrent files or magnet links. Downloaded data on disk is not affected. rTorrent re-checks existing data when you re-add the torrent.

On PM seedboxes, rTorrent is monitored by a dual-level redundancy system that restarts it automatically if it crashes. Session corruption from crashes is rare but still happens after unexpected reboots or disk-full conditions.

See Removing rTorrent session data and Restarting rTorrent for detailed instructions.

Tracker connectivity

The tracker tells your client where the peers are. If the client cannot reach the tracker, it cannot find peers, and the download stalls.

Common tracker problems:

DNS failure: The tracker hostname does not resolve. Try changing your DNS to 1.1.1.1 or 8.8.8.8. On a PM seedbox, DNS is configured at the server level and this is not an issue.
Tracker down: The tracker server itself is offline. Check the tracker website. Nothing you can do but wait.
Blocked by ISP: Some ISPs block connections to known tracker domains or ports. The same ISP throttling problem as above.
Passkey expired: On private trackers, your passkey may have been revoked if your account was disabled. Re-download the .torrent from the tracker website.

If the tracker status shows "connection timed out" repeatedly but the tracker website loads in your browser, the port may be blocked or the connection throttled. A seedbox running on datacenter transit does not have these blocks.

Client configuration

Some stalls are caused by torrent client settings that are too aggressive for the available connection:

Too many active torrents: Each active torrent uses connections, memory, and disk I/O. Running 500 active torrents on a home connection with 4GB RAM causes the client to choke. On a PM seedbox, the server handles dozens to hundreds of active torrents per user depending on the plan tier and available resources.
Global connections too high: Setting 1,000 max connections on a connection that cannot handle it causes timeouts. The default settings in rTorrent, Deluge, and qBittorrent on PM seedboxes are tuned for the server hardware.
DHT disabled: If DHT is off and the tracker goes down, the client loses all peer sources. PM seedboxes allow DHT on all plans.

What to check (in order)

Peer count: Are there any seeders? If not, the torrent is dead.
Tracker status: Is the tracker reporting an error? Look in the torrent details.
Disk space: Is the disk full? Run quota -s on a PM seedbox.
Client running: Did rTorrent, Deluge, or qBittorrent crash? Check the web interface.
ISP throttling: Try the same torrent from a different network. If it works elsewhere, the ISP is the problem.

If you are on a PM seedbox and none of the above apply, open a support ticket. Include the torrent name and the tracker error message.