A zero-copy FTP daemon built for speed, correctness, and portability.
Runs anywhere POSIX runs. Saturates Gigabit. Ships a console payload too.

Overview · Performance · Features · Best Setup · Build · Running · Configuration · ZHTTP

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Overview

zftpd is a high-performance FTP server written in C11. It was designed around a single idea: the data path should be as fast as the hardware allows, with no unnecessary work anywhere between file and socket.

In practice, this means using sendfile where the OS supports it, keeping the hot path free of allocations, and handling TCP backpressure correctly so the pipe never stalls under load. The result is an FTP daemon that saturates a full Gigabit Ethernet link in both directions — on Linux, macOS, or any POSIX-compliant system — without any client-side tuning.

The same binary model also targets PS4 and PS5 as console payloads, with on-screen notifications and an optional browser-based file explorer. This is an extension of the same codebase, not a fork — the POSIX foundation is identical.

Philosophy
  ├── Keep the data path fast          →  sendfile fast path, zero-copy where available
  ├── Handle TCP correctly             →  partial sends, EINTR, backpressure-aware buffers
  ├── Stay portable                    →  C11, POSIX, standard toolchain
  ├── Be predictable under load        →  no dynamic allocation per transfer, no surprises
  └── Extras are opt-in               →  encryption, rate limiting, web UI — all compile-time

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⚡ Performance

zftpd saturates a full Gigabit Ethernet link — ~112 MB/s sustained in both directions.

This is the physical ceiling of a 1 GbE connection. It is achieved out of the box, with no kernel tuning required.

  Benchmark — single stream, wired 1 GbE, plain transfer

  Download  ████████████████████████████████████████████  112 MB/s
  Upload    █████████████████████████████████████████     108 MB/s
                                                          ────────
  Physical ceiling (1 GbE)                                125 MB/s

What makes it fast:

Technique	What it does
sendfile kernel fast path	Moves file data directly to the socket — zero userspace copies
Partial-send loop	Handles short writes without stalling or corrupting the stream
EINTR-safe I/O	Signal interrupts are absorbed cleanly in the hot loop
Allocation-free transfer path	No malloc, no locking per packet or per transfer
Token-bucket limiter is opt-in	Adds zero overhead when rate limiting is not needed

On encryption: enabling AUTH XCRYPT (ChaCha20) disables sendfile and switches to buffered I/O. Throughput becomes CPU-bound. For maximum speed on a trusted network, use plain transfers — that is what sendfile is there for.

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✦ Features

Transfer engine sendfile zero-copy fast path (Linux · BSD · macOS) Fallback to buffered I/O when encrypted Backpressure-aware send loop, EINTR-safe Upload resume: REST + STOR Append mode: APPE Transfer rate limiting via token bucket (compile-time, opt-in) Connection handling Active mode: PORT Passive mode: PASV, EPSV Control and data channel timeouts Session idle timeout Up to FTP_MAX_SESSIONS concurrent sessions

Security Path canonicalization — no traversal possible Optional blocklist for /dev, /proc, /sys Optional ChaCha20 stream cipher with PSK (AUTH XCRYPT) Observability Structured per-session logging Transfer stats: bytes sent/received, files transferred Per-command logging (compile-time toggle) Platform extras Linux, macOS, PS4, PS5 On-screen IP/port notification on PS4 and PS5 ZHTTP web file explorer (compile-time, see ZHTTP)

Complete FTP command reference

Group	Commands
Authentication	USER PASS QUIT NOOP
Navigation	CWD CDUP PWD
Directory listing	LIST NLST MLSD MLST
File transfer	RETR STOR APPE REST
File management	DELE RMD MKD RNFR RNTO
Data connection	PORT PASV EPSV
Metadata	SIZE MDTM STAT SYST FEAT HELP
Transfer parameters	TYPE MODE STRU
Negotiation	OPTS CLNT
Site extensions	SITE CHMOD
Encryption	AUTH XCRYPT — ChaCha20 with PSK (opt-in)

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🛠 Best Setup

Network — wired is the only choice

zftpd performs at the physical limit of your network. The bottleneck is almost always the medium, not the software. Wi-Fi is the bottleneck — even Wi-Fi 6 introduces retransmissions and variable latency that collapse sustained FTP throughput. Use a wired connection.

The optimal topology is a direct Ethernet cable between source and destination, eliminating every unnecessary hop:

  [Source machine]
        │
  Ethernet cable
        │
  [Destination machine]

If a switch is needed, any Gigabit switch works. Avoid powerline adapters and MoCA bridges — they introduce jitter that disrupts sustained transfers.

Assign static IPs on both ends (e.g. 192.168.100.1 / 192.168.100.2). This removes DHCP latency and keeps the setup fully deterministic.

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FTP clients

Client	Platform	Recommendation
FileZilla	Windows · macOS · Linux	Best general-purpose choice. Enable parallel transfers for directory trees.
WinSCP	Windows	Excellent throughput and error recovery.
lftp	Linux · macOS	Best CLI option. pget -n 4 enables parallel chunked downloads.
Cyberduck	macOS · Windows	Solid for occasional transfers.
OS built-in FTP	any	❌ Avoid — artificially capped speeds, no resume support.

Things that matter on the client side:

• Transfer mode must be Binary (TYPE I). zftpd defaults to Binary, but a misconfigured client can override this silently — always verify.
• Use passive mode (PASV). It's the default and works cleanly behind NAT and firewalls. Active mode requires the server to reach back to the client and is frequently blocked.
• Enable parallel connections for large directory trees. FileZilla exposes this under Site Manager → Transfer Settings. It will not increase single-file speed, but dramatically reduces total time for many small files.
• Disable client-side CRC or integrity checks if offered. TCP guarantees delivery; checksumming again adds latency for no benefit.

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Linux — optional kernel tuning

zftpd reaches full Gigabit speed with default kernel parameters. If you are feeding a very fast NVMe drive into the network and want to raise the ceiling further:

# Raise socket buffer limits — run as root, optional
sysctl -w net.core.rmem_max=134217728
sysctl -w net.core.wmem_max=134217728
sysctl -w net.ipv4.tcp_rmem="4096 87380 134217728"
sysctl -w net.ipv4.tcp_wmem="4096 65536 134217728"

To make these persistent, add them to /etc/sysctl.conf.

PS4 / PS5 — console-specific notes

• zftpd requires a payload loader to run on console (WebKit / PPPwn / GoldHEN on PS4; etaHEN or equivalent on PS5). The daemon itself does not require a resident HEN.
• Launch after the system is fully booted and the loader is ready. The on-screen notification will display the IP and port.
• For maximum throughput: direct cable from console to PC, static IPs, no router in between.
• Avoid initiating transfers while background downloads or system updates are active — the network stack is shared.
• If you see "payload already loaded": a previous instance is still active. zftpd will attempt to terminate it and restart on the default port. If that fails, it tries up to 9 subsequent ports (FTP_DEFAULT_PORT+1 … +9).

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📦 Build

Output artifacts are versioned and platform-tagged, placed in build/<target>/<build_type>/.

Requirements

Compiler	C11 — gcc or clang
Build system	make
.bin generation	objcopy (binutils or llvm-objcopy); PS4: orbis-objcopy; PS5: prospero-objcopy
PS4	PS4_PAYLOAD_SDK set in environment
PS5	PS5_PAYLOAD_SDK set in environment

Commands

# Targets
make TARGET=linux
make TARGET=macos
make TARGET=ps4
make TARGET=ps5

# Modifiers
make TARGET=linux BUILD_TYPE=debug
make TARGET=linux ENABLE_ZHTTPD=1     # enable web UI (off by default on POSIX)
make TARGET=ps5   ENABLE_ZHTTPD=0     # disable web UI (on by default on console)

# Tests (POSIX only)
make TARGET=linux test
make TARGET=macos test

Artifacts

Platform	Output
Linux	build/linux/release/zftpd-linux-<arch>-v<ver>.elf
macOS	build/macos/release/zftpd-macos-<arch>-v<ver>
PS4	zftpd-ps4-v<ver>.bin · zftpd-ps4-v<ver>.elf
PS5	zftpd-ps5-v<ver>.bin · zftpd-ps5-v<ver>.elf

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🚀 Running

Linux

./build/linux/release/zftpd-linux-<arch>-v<version>.elf [-p <port>] [-d <root>]

macOS

./build/macos/release/zftpd-macos-<arch>-v<version> [-p <port>] [-d <root>]

PS4

Send .bin to your payload loader, or .elf if the loader accepts ELF directly.
On startup: on-screen notification displays IP and port.

PS5

Send .bin or .elf depending on your loader.
On startup: FTP: <ip>:<port> notification.

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⚙️ Configuration

All configuration is compile-time, in include/ftp_config.h.

Macro	Default	Notes
FTP_DEFAULT_PORT	2121 (POSIX) · 2122 (console)	Listening port
FTP_MAX_SESSIONS	—	Maximum concurrent client sessions
FTP_SESSION_TIMEOUT	—	Idle session timeout
FTP_TRANSFER_RATE_LIMIT_BPS	disabled	Token-bucket average rate cap
FTP_TRANSFER_RATE_BURST_BYTES	disabled	Token-bucket burst allowance
FTP_LOG_COMMANDS	—	Log every received command

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🌐 ZHTTP

ZHTTP is a lightweight HTTP server embedded in zftpd that serves a browser-based file explorer. It allows browsing, downloading, and optionally uploading files from any browser on the local network — no FTP client required.

Target	Default	To override
PS4 / PS5	✅ on	make TARGET=ps5 ENABLE_ZHTTPD=0
Linux / macOS	❌ off	make TARGET=linux ENABLE_ZHTTPD=1

Once the daemon is running, open http://<ip>:<port>/ — the HTTP port mirrors the configured FTP port.

Upload support is enabled automatically alongside ZHTTP (ENABLE_WEB_UPLOAD=1).

Security: ZHTTP has no authentication beyond network access. It is designed for local-network use. Do not expose it on a public interface.

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Acknowledgements

hippie68 — PS4 FTP reference implementation
John Törnblom — PS5 payload framework
PlayStation homebrew community — testing and feedback

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Released under the MIT License