pyomq

Python binding for omq.rs, a Rust libzmq port. Drop-in pyzmq replacement on the common path.

Highlights

• Sync and asyncio APIs with all 20 ZMTP socket types.
• Standard sockets: PAIR, PUB, SUB, REQ, REP, DEALER, ROUTER, PULL, PUSH, XPUB, XSUB, and STREAM.
• Draft sockets: SERVER, CLIENT, RADIO, DISH, GATHER, SCATTER, PEER, and CHANNEL.
• tcp://, ipc://, inproc://, verified TLS quic://, dart://, and udp:// transports (udp:// is RADIO/DISH only).
• Optional plain, curve, lz4, zstd, quic, and dart features in the published wheel.
• Built on omq-tokio; runtime work runs on a dedicated background thread and Python calls release the GIL across the runtime trip.
• RADIO/DISH groups use socket.join() / socket.leave(), socket.send(body, group="..."), and Frame.group on receive.

Install

Requires Python 3.12+. Wheels use the cp312-abi3 stable ABI.

uv pip install pyomq

The standard build includes optional features: plain, curve, lz4, zstd, quic, dart. Use pyomq.has("curve") at runtime to check availability.

Published wheels target Linux, macOS, and Windows on x86-64 and ARM64. Other platforms can build from sdist.

Usage

import pyomq as zmq  # drop-in for `import zmq` from pyzmq

ctx = zmq.Context()
push = ctx.socket(zmq.PUSH)
push.connect("tcp://127.0.0.1:5555")
push.send(b"hello")
push.close()
ctx.term()

For asynchronous code:

import pyomq
import pyomq.asyncio as zmq_async

ctx = zmq_async.Context()
sock = ctx.socket(pyomq.PUSH)
sock.connect("tcp://127.0.0.1:5555")
await sock.send(b"hello")
sock.close()

Zguide-style runnable examples live in examples/zguide/.

Buffers, tracking, and types

send() accepts pyomq.Sendable: buffer-protocol objects and Frame. send_multipart() also accepts generators of these values. Buffers must be contiguous; multidimensional and multibyte buffers are sent as raw bytes. Use send_string() for text. __bytes__ alone does not make an object sendable.

With copy=False, track=True, sends return a MessageTracker; asyncio sends resolve to that tracker when awaited. tracker.done and tracker.wait(timeout) indicate when borrowed buffers are no longer in use, not peer delivery. Timeouts are in seconds; wait() raises NotDone when the deadline expires. Do not mutate borrowed data before completion. Keeping a zero-copy Frame, an exported view, or an inproc receiver's frame alive can delay completion. Multipart tracking covers every part. Copied buffer sends return None, even with track=True. Sending a Frame returns its own tracker; requesting tracking on an untracked frame raises ValueError.

wait() blocks its calling thread. In asyncio code, awaiting send() only waits for queue admission. Use await asyncio.to_thread(tracker.wait) when you need buffer completion without blocking the event loop.

Python-defined buffer exporters may run __release_buffer__ on an I/O thread. Release callbacks must not make blocking socket or context calls: those calls can deadlock the I/O thread. Use copy=True for such exporters or hand their cleanup work to an application thread. This limitation also applies when tracking is disabled.

Tracking adds bookkeeping only when requested. For repeated sends of unchanged data, a tracked Frame reuses its tracking state across sends. Its tracker still cannot finish until the frame and every outstanding user release it.

The package includes native stubs and precise sync/async receive overloads. copy=False returns Frame values, and a runtime boolean yields the union of byte and frame result types. Serialization callbacks retain their return types; socket options, authentication policies, and monitor events are typed.

PLAIN servers require an explicit policy before bind. Use fixed credentials with pull.plain_server = 1; pull.set_plain_auth([("alice", "secret")]), or pass a callable to set_plain_auth. Clients keep using plain_username and plain_password. PLAIN does not encrypt traffic.

Performance

See COMPARISONS.md for full tables.

2-process loopback throughput and latency vs pyzmq, measured on Linux 6.12 (Debian 13), Intel i7-8700B 3.2 GHz, Rust 1.95.0.

zmq.proxy() forwarding (128 B, TCP)

pyomq's proxy() forwards directly between sockets on the tokio runtime, no Python per-message overhead. pyzmq's zmq.proxy() calls libzmq's C-level zmq_proxy. PUSH/PULL forwarding is throughput-bound; REQ/REP proxy is latency-bound (4 TCP hops per round-trip).

Run scripts/update_perf.py (after maturin develop --release) to re-measure, regenerate the chart, and update the proxy table.

Compression transports

OMQ.rs adds transparent compression transports on top of TCP: lz4+tcp:// and experimental zstd+tcp://. Swap the scheme in your endpoint string and everything else stays the same:

push = ctx.socket(zmq.PUSH)
push.bind("lz4+tcp://127.0.0.1:5555")

pull = ctx.socket(zmq.PULL)
pull.connect("lz4+tcp://127.0.0.1:5555")

Both peers must use a matching compression endpoint. Payloads below the transport threshold are sent as-is when compression would not help.

Compression transports support static dictionaries and dictionary auto-training (off by default). Auto-training samples outbound messages, builds a 2 KiB dict, and ships it once per connection. Static dicts are set with compression_dict. zstd+tcp:// also accepts compression_level. Pure Rust (lz4rip / zrip), no C compiler required.

Enable it on sockets that send compressible traffic before bind()/connect():

push.compression_auto_train = 1
# or: push.setsockopt(zmq.OMQ_COMPRESSION_AUTO_TRAIN, 1)
push.compression_level = 1  # zstd+tcp only

See BENCHMARKS_COMPRESSION.md for throughput charts and benchmark details. Wire formats: LZ4, Zstd.

QUIC

quic:// carries reliable ZMTP messages over TLS 1.3. Check availability with pyomq.has("quic"). Set QUIC options before the socket's first bind/connect; later changes raise ZMQError. Sync and asyncio sockets use the same options.

from pathlib import Path

server = ctx.socket(pyomq.REP)
server.quic_cert_pem = Path("server.pem").read_bytes()
server.quic_key_pem = Path("server.key").read_bytes()
server.bind("quic://127.0.0.1:5555")

client = ctx.socket(pyomq.REQ)
client.quic_trust_system = 0
client.quic_trust_pem = Path("ca.pem").read_bytes()
client.quic_server_name = b"localhost"
client.connect("quic://127.0.0.1:5555")

System certificate roots are enabled by default. quic_server_name overrides the verified name; it does not disable verification. The optional quic_stream_window is a byte window (16 KiB to 256 MiB), not a message size limit. quic_max_ready_peers defaults to 1024. The corresponding OMQ_QUIC_* constants also work with setsockopt()/getsockopt().

Build the Rust test peer before running the cross-process tests:

cargo build -p omq-tokio --features quic --example quic_interop_peer
cd bindings/pyomq
OMQ_QUIC_INTEROP_REQUIRED=1 pytest tests/test_quic_interop.py

CURVE authentication

CURVE encrypts traffic and authenticates the server to the client. To also authenticate clients to the server, call set_curve_auth() before bind()/connect():

server_pub, server_sec = zmq.curve_keypair()
client_pub, client_sec = zmq.curve_keypair()

pull = ctx.socket(zmq.PULL)
pull.curve_server = 1
pull.curve_publickey = server_pub
pull.curve_secretkey = server_sec

# Option 1: allow specific client keys (checked in Rust, no GIL overhead)
pull.set_curve_auth([client_pub])

# Option 2: custom callback. PeerInfo has .public_key (Z85) and
# .identity (bytes or None).
pull.set_curve_auth(lambda peer: peer.public_key in allowed_keys)

# Option 3: accept any valid CURVE client (the default)
pull.set_curve_auth(None)

No ZAP, no filesystem key management. The callback runs during the CURVE handshake; returning a falsy value rejects the client.

On ROUTER and PEER, recv_from() returns an owning identity and all body frames; copy=False returns Frame objects, and the asyncio API is awaitable. The identity retains the admission snapshot across reconnects and socket closure; authentication contains verified facts, while diagnostics is for logging.

identity, frames = router.recv_from()
info = identity.peer_info
key = info.authentication.public_key  # raw CURVE key bytes, or None
endpoint = info.diagnostics.endpoint
router.send_to(identity, [b"reply"])  # route bytes may now select a replacement peer

Develop

cd bindings/pyomq
uv venv && source .venv/bin/activate
uv pip install maturin pyzmq pytest pytest-asyncio pytest-timeout
maturin develop --release
pytest -v