Flud proxy on Android: one documented line, and how to measure the rest from outside the phone

Flud is the most-installed independent torrent app on Android, with more than 10 million downloads, and its proxy support is documented in exactly one line of its Google Play listing: "Proxy Support for trackers and peers." Which proxy types it accepts, whether it takes a username and password, where the setting lives, which engine it runs and what it does with DHT and other UDP are not published by the developer. The only how-to pages we found were proxy vendors' marketing, which is not evidence. We did not run Flud ourselves.

So this page does not describe Flud's settings screen. It describes how to find out what the app sends, from outside the phone, without rooting it.

#What holds regardless of the app

Our SOCKS5 should be treated as TCP only, since we do not advertise UDP relay: DHT, UDP trackers and uTP will not work through it even if Flud could relay UDP. An HTTP proxy carries no UDP at all. A proxy does not encrypt your traffic, and anything the app sends around it shows your own address, which on a phone may be your mobile carrier's or your home line's. Residential traffic, and a shared IP's traffic past its included gigabyte, is billed per GB, so a torrent you keep seeding from the phone is billed on the way out too; the terms explain the count. The qBittorrent project's wiki tells users worried about copyright enforcement to use a VPN, and that advice is not client-specific. This page is about lawful downloads, like a Linux image or an open dataset; using our proxies for unauthorised sharing is not allowed by the allowed-use policy.

#Before the test

• Enter your proxy in Flud's settings. If the app offers credential fields, use the username and password from your order. If it does not, add the network's public IP to the order's IP allowlist; our Android proxy guide explains why Android's own proxy screen has no password fields either.
• Turn on Flud's option to download on Wi-Fi only, so nothing escapes over mobile data where you cannot see it.
• Note the proxy's IP address and its exit address. The curl line on our proxy checker, run from a computer through the same proxy, prints the exit.

#The differential capture

A phone talks to the internet all the time, so a single capture cannot tell Flud's packets from everything else. Two captures can.

1. On a Linux laptop, share a Wi-Fi hotspot and connect the phone to it. Note the phone's address on the hotspot network.
2. With Flud stopped, capture one minute of what the phone sends anywhere other than the proxy:

PHONE=10.42.0.50
PROXY_IP=203.0.113.10
sudo timeout 60 tcpdump -nni wlan0 -w idle.pcap "src host $PHONE and not dst host $PROXY_IP and not port 53"

3. Start a lawful torrent in Flud, wait two minutes, and capture another minute to active.pcap with the same filter.
4. Compare the two:

for f in idle.pcap active.pcap; do
  echo "$f: $(tcpdump -nnr $f 2>/dev/null | wc -l) packets, $(tcpdump -nnr $f 2>/dev/null | awk '{print $5}' | cut -d. -f1-4 | sort -u | wc -l) destinations"
done
tcpdump -nnr active.pcap udp 2>/dev/null | head

If Flud proxies trackers and peers and drops UDP, the active minute looks like the idle one, plus a steady stream of connections to the proxy that your filter hides. If the active minute shows many new destinations, or a run of UDP packets the idle one did not have, those are the app's own connections going around the proxy, most likely DHT or peers. In Wireshark, the same comparison is the filter ip.src == PHONE && !(ip.dst == PROXY_IP) on each file.

#Reading the result

The app is maintained; the Play listing showed an update on Sep 27, 2026, though we could not confirm its version number. Re-run the capture after an update rather than assuming a setting kept its meaning.

#Cost on a phone

Phones are a sensible place to fetch an image and a poor place to seed one. Downloading a 2 GB distribution image through proxied peers is $10.40 on residential at checkout; seeding it back to a ratio of 1.0 doubles the traffic, to $20.80. An ISP IP is $3.20/IP (dedicated) a month with no bandwidth cap, if you seed from the phone regularly. Peer-to-peer traffic for lawful content is fine on residential and on dedicated ISP and datacenter IPs, which carry no traffic meter. The cost calculator compares the two.

The torrent client comparison lists Flud with the clients whose proxy behaviour is mostly undocumented, next to desktop clients that publish theirs, such as BiglyBT.