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udpscope/tools/mock_udpstreamer.py
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#!/usr/bin/env python3
# SPDX-License-Identifier: MIT
# SPDX-FileCopyrightText: 2026 Martino Ferrari
"""A minimal UDPStreamer (UDPS) producer, for exercising udpscope without MARTe2.
Unicast only: binds `--port`, waits for a CONNECT datagram, then streams CONFIG
once and DATA packets to whoever connected. Publish mode is Accumulate, so each
packet carries `--batch` consecutive samples per (scalar) signal -- the shape the
viewer's per-sample path expects.
Signals: `time` (the stream's own clock, seconds), `sine`, `square`, `ramp`.
Everything is float64 and unquantised.
./tools/mock_udpstreamer.py --port 8000 --rate 10000 --batch 100
"""
import argparse
import math
import random
import socket
import struct
import time
import numpy as np
MAGIC = 0x53504455
PKT_DATA, PKT_CONFIG, PKT_ACK, PKT_CONNECT, PKT_DISCONNECT = 0, 1, 2, 3, 4
T_FLOAT64 = 9
QUANT_NONE = 0
TIME_PACKET, TIME_FULL_ARRAY, TIME_FIRST_SAMPLE = 0, 1, 2
PUBLISH_ACCUMULATE = 1
NO_TIME_SIGNAL = 0xFFFFFFFF
def header(pkt_type, counter, payload_bytes):
return struct.pack("<IBIHHI", MAGIC, pkt_type, counter, 0, 1, payload_bytes)
def signal_desc(name, *, rate, time_mode, time_idx, unit, rows=1, cols=1, dims=0):
"""One 136-byte signal descriptor."""
d = bytearray(136)
d[0:64] = name.encode()[:64].ljust(64, b"\0")
d[64] = T_FLOAT64
d[65] = QUANT_NONE
d[66] = dims
struct.pack_into("<II", d, 67, rows, cols)
struct.pack_into("<dd", d, 75, -10.0, 10.0)
d[91] = time_mode
struct.pack_into("<d", d, 92, rate)
struct.pack_into("<I", d, 100, time_idx)
d[104:136] = unit.encode()[:32].ljust(32, b"\0")
return bytes(d)
def build_config(rate, time_mode=TIME_FULL_ARRAY, unit="V"):
sigs = [
# The stream's clock: referenced by every data signal, so udpscope treats
# it as the time base rather than a plottable channel. Its *own* time_mode
# is what udpscope switches on, so `--time-mode first` has to land here.
signal_desc(
"time", rate=0.0, time_mode=time_mode, time_idx=NO_TIME_SIGNAL, unit="s"
),
signal_desc("sine", rate=rate, time_mode=time_mode, time_idx=0, unit=unit),
signal_desc("square", rate=rate, time_mode=time_mode, time_idx=0, unit=unit),
signal_desc("ramp", rate=rate, time_mode=time_mode, time_idx=0, unit=unit),
signal_desc("noise", rate=rate, time_mode=time_mode, time_idx=0, unit=unit),
]
payload = struct.pack("<I", len(sigs)) + b"".join(sigs)
payload += bytes([PUBLISH_ACCUMULATE])
return header(PKT_CONFIG, 0, len(payload)) + payload
def build_data(
counter,
t0,
dt,
batch,
freq,
time_mode=TIME_FULL_ARRAY,
noise=0.0,
time_spike=0.0,
glitch_at=-1.0,
glitch_width=0.0,
quiet_at=-1.0,
):
stamps = [t0 + i * dt for i in range(batch)]
# `time_spike` models a device whose clock glitches for one packet: the stamps jump
# far ahead and then the next packet carries on from where it would have been. The
# waveforms are still computed from the *true* stamps, so only the time signal is
# wrong -- which is what a glitching clock looks like on the wire.
wire_stamps = [t + time_spike for t in stamps] if time_spike > 0.0 else stamps
# The interferer is a tone at 100x the fundamental with a randomly scaled amplitude, which
# is the shape that is hardest on anything counting crossings: near the sine's own mid level
# the fundamental's slope is 2*pi*f while the interferer's is 100x that, so the signal
# recrosses the level several times per true crossing. `--noise 0` is the ideal waveform, and
# it is the default because the documented probe assertions are *exact* (`peak to peak=2`,
# `top=0.636620`) and any interferer moves the extremes.
if noise > 0.0:
sine = [
math.sin(2.0 * math.pi * freq * t)
+ random.random() * noise * math.sin(2.0 * math.pi * 100.0 * freq * t)
for t in stamps
]
else:
sine = [math.sin(2.0 * math.pi * freq * t) for t in stamps]
square = [
1.0 if math.sin(2.0 * math.pi * freq * 0.5 * t) >= 0.0 else -1.0 for t in stamps
]
ramp = [(freq * t) % 1.0 * 2.0 - 1.0 for t in stamps]
noisy = np.sin(100 * math.pi * np.array(stamps) + 0.5) + np.random.normal(
0, 0.5, batch
)
# A glitch is an *inversion* of the square for `glitch_width` seconds, repeated once per
# square period (2/freq -- the period of sin(2*pi*freq*0.5*t)). Inverting rather than
# forcing a level makes it a narrow pulse whatever the square's polarity is, and repeating
# it lets a probe assert the *spacing* of the hits a width condition finds instead of an
# absolute count, which depends on when the probe happened to start looking.
if glitch_at >= 0.0 and glitch_width > 0.0:
sq_period = 2.0 / freq
for i, t in enumerate(stamps):
if t < glitch_at:
continue
k = math.floor((t - glitch_at) / sq_period)
start = glitch_at + k * sq_period
if t < start + glitch_width:
square[i] = -square[i]
# `--quiet-at` is for the dropout condition: the sine stops at a level on the *opposite*
# side of zero from where it was, so `quiet_at` itself is its last zero crossing and a
# dropout at level 0 fires at exactly `quiet_at + timeout`. Holding at the same sign would
# leave the last crossing at whichever earlier zero happened to precede it, which is not a
# figure a probe can assert. Choose a `quiet_at` away from the sine's own zeros.
if quiet_at >= 0.0:
held = -0.5 if math.sin(2.0 * math.pi * freq * quiet_at) >= 0.0 else 0.5
for i, t in enumerate(stamps):
if t >= quiet_at:
sine[i] = held
# In FIRST_SAMPLE mode only element 0 of the time signal is meaningful: the producer
# stamps the first sample of the batch and says nothing about the rest. A scalar
# signal in Accumulate mode still occupies `batch` slots on the wire (the client
# reads `num_samples` values for any 1-element signal), so the anchor is repeated --
# which is exactly the shape that made udpscope derive a step of zero.
wire_time = (
[wire_stamps[0]] * batch if time_mode == TIME_FIRST_SAMPLE else wire_stamps
)
payload = struct.pack("<QI", int(t0 * 1e9), batch)
for arr in (wire_time, sine, square, ramp, noisy):
payload += struct.pack("<%dd" % batch, *arr)
return header(PKT_DATA, counter, len(payload)) + payload
def main():
ap = argparse.ArgumentParser()
ap.add_argument("--port", type=int, default=8000)
ap.add_argument("--rate", type=float, default=10000.0, help="samples per second")
ap.add_argument("--batch", type=int, default=100, help="samples per packet")
ap.add_argument("--freq", type=float, default=5.0, help="waveform frequency, Hz")
ap.add_argument("--duration", type=float, default=0.0, help="0 = forever")
ap.add_argument(
"--stream-scale",
type=float,
default=1.0,
help="stream seconds per wall second: 0.1 mimics a producer whose own "
"clock advances ten times slower than the wire delivers samples",
)
ap.add_argument(
"--declared-rate",
type=float,
default=-1.0,
help="sampling_rate to put in CONFIG; -1 = the real rate, 0 = 'unknown'",
)
ap.add_argument(
"--time-mode",
choices=("full", "first"),
default="full",
help="how the stream carries its clock: 'full' stamps every sample "
"(UDPS_TIME_FULL_ARRAY), 'first' stamps only the batch's first "
"sample (UDPS_TIME_FIRST_SAMPLE) and leaves the viewer to space the "
"rest by the declared cadence -- the shape a real MARTe2-style "
"producer with a single u64 clock has",
)
ap.add_argument(
"--unit",
default="V",
help="the unit the data signals declare in CONFIG; '' declares none, which "
"is an ordinary stream (and what every math channel looks like) and is "
"the only way a probe can see the unitless readout formatting",
)
ap.add_argument(
"--noise",
type=float,
default=0.0,
help="amplitude of an interferer added to `sine`: a tone at 100x the fundamental, "
"scaled by a fresh uniform random factor per sample. 0 = the ideal sine, which is "
"what the exact probe assertions (peak to peak = 2, top = 2/pi) are read against; "
"0.1 is the figure the measurement hysteresis is sized against",
)
ap.add_argument(
"--clock-jitter",
type=float,
default=0.0,
help="per-packet stamp jitter, as a fraction of one packet's span: a device "
"that stamps each batch from its own clock does not land on a perfect "
"grid, so the stream's timestamps wobble about one. Non-cumulative "
"(the mean rate is unchanged); 0 = the ideal grid",
)
ap.add_argument(
"--time-glitch-at",
type=float,
default=-1.0,
help="stream time (s) at which ONE packet's time signal jumps ahead by "
"--time-glitch-by and then carries on normally: a device whose clock "
"glitches. -1 = never",
)
ap.add_argument(
"--time-glitch-by",
type=float,
default=10.0,
help="how far ahead the glitching packet's stamps jump, in stream seconds",
)
ap.add_argument(
"--glitch-at",
type=float,
default=-1.0,
help="stream time (s) of the first narrow pulse injected into `square`: the square "
"is inverted for --glitch-width seconds, once per square period (2/freq), so a "
"pulse-width or glitch trigger has a repeating event to find. -1 = never",
)
ap.add_argument(
"--glitch-width",
type=float,
default=0.002,
help="width of each injected pulse, in stream seconds (default 0.002 s; a zero width "
"silently disables the glitch even when --glitch-at is set)",
)
ap.add_argument(
"--quiet-at",
type=float,
default=-1.0,
help="stream time (s) after which `sine` is held at a constant level on the "
"opposite side of zero, so --quiet-at is its last zero crossing: the shape a "
"dropout trigger is read against. -1 = never",
)
ap.add_argument(
"--blackout-at",
type=float,
default=0.0,
help="seconds after start at which the stream goes silent (EMI link loss)",
)
ap.add_argument(
"--blackout",
type=float,
default=0.0,
help="seconds the stream stays silent; must exceed the client's 2 s silence timeout",
)
ap.add_argument(
"--drop-every",
type=int,
default=0,
help="withhold every Nth DATA packet from the wire -- packet loss. Deterministic "
"rather than a probability for the reason --glitch-at gives: a probe asserts the "
"spacing of the events it finds, and a random count is not a figure. The counter "
"and the stream clock advance over a withheld packet, which is the whole point: "
"the receiver orders the stream by the counter alone, so that is the only thing "
"that tells it a packet existed. 0 = never",
)
ap.add_argument(
"--drop-burst",
type=int,
default=1,
help="consecutive packets each --drop-every event withholds: one models a lost "
"datagram, a long run models a link that went away. The run length is what the "
"ingest's own glitch guard is sized against, since it bridges a packet whose "
"stamps jump more than 256 packet spans ahead. Measured at 1000 packets a second, "
"a burst of 200 is counted as loss and nothing else; one of 300 is read as a clock "
"glitch instead, and because each bridge advances the anchor by one packet span "
"while the true timeline is 300 ahead, the four following packets fail too and the "
"stream falls back to arrival timing. Keep a burst under the 2 s silence timeout "
"or the client reconnects and the mock restarts its clock, which is a different "
"test",
)
ap.add_argument(
"--reorder-every",
type=int,
default=0,
help="hold every Nth packet back and send it after the next one that goes out -- "
"an inversion on the wire. What the receiver does depends on how late the held "
"packet arrives: inside the 20 ms reorder window it is resequenced with no hole; "
"past it a hole is committed first and the packet backfills it. "
"--reorder-delay-ms controls which path is taken (see its help). "
"A --drop-every that swallows the packet after a held one deepens the inversion "
"rather than cancelling it, since the held packet waits for the next packet "
"actually sent. 0 = never",
)
ap.add_argument(
"--reorder-delay-ms",
type=float,
default=0.0,
metavar="MS",
help="hold a withheld packet this many milliseconds instead of releasing it "
"immediately behind the packet that overtook it. Under the receiver's reorder "
"window the packet is resequenced and no hole is ever seen; past it the hole is "
"committed first and the packet has to backfill it -- which is the only way to "
"reach the backfill path at all, since a 0 ms delay always wins the race.",
)
args = ap.parse_args()
dt = args.stream_scale / args.rate # stream seconds per sample
period = args.batch / args.rate # wall seconds per packet
declared = args.rate if args.declared_rate < 0.0 else args.declared_rate
time_mode = TIME_FIRST_SAMPLE if args.time_mode == "first" else TIME_FULL_ARRAY
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind(("0.0.0.0", args.port))
sock.settimeout(0.001)
print(
"mock udpstreamer: waiting for CONNECT on :%d (%.0f S/s wire, %d per packet, "
"stream clock x%.3g, declared %.0f S/s, time-mode %s)"
% (
args.port,
args.rate,
args.batch,
args.stream_scale,
declared,
args.time_mode,
),
flush=True,
)
peer = None
counter = 1
glitched = False
t_stream = 0.0
started = None
next_send = time.monotonic()
held = None # (counter, datagram, release_deadline) built but withheld, for --reorder-every
drop_left = 0
dropped = 0
blackout_left = 0.0
blackout_done = False
inverted = 0
noted_drop = False
noted_reorder = False
while True:
try:
buf, addr = sock.recvfrom(2048)
if len(buf) >= 17:
magic, ptype = struct.unpack_from("<IB", buf, 0)
if magic == MAGIC and ptype == PKT_CONNECT:
peer = addr
counter = 1
glitched = False
t_stream = 0.0
started = time.monotonic()
next_send = started
held = None
drop_left = 0
sock.sendto(build_config(declared, time_mode, args.unit), peer)
print(
"mock udpstreamer: CONNECT from %s:%d, CONFIG sent" % peer,
flush=True,
)
elif magic == MAGIC and ptype == PKT_DISCONNECT:
print("mock udpstreamer: DISCONNECT", flush=True)
peer = None
except socket.timeout:
pass
if peer is None:
continue
now = time.monotonic()
# An EMI-style link loss: the producer keeps making samples but nothing gets
# through, so the client's silence timeout -- not a polite DISCONNECT -- is
# what ends the session, which is the case recovery has to survive.
if blackout_left > 0.0:
blackout_left -= 0.002 # the loop polls at most every 2 ms
if blackout_left <= 0.0:
print("mock udpstreamer: blackout over, resuming", flush=True)
elif (
args.blackout_at > 0.0
and args.blackout > 0.0
and not blackout_done
and started is not None
and now - started >= args.blackout_at
):
blackout_done = True
blackout_left = args.blackout
print(
f"mock udpstreamer: blackout for {args.blackout} s (link loss)",
flush=True,
)
if blackout_left > 0.0:
# Silent: the producer falls behind the wall clock, and when the link
# returns it resumes from *now* -- the backlog is what the link ate.
next_send = now
time.sleep(0.002)
continue
if now < next_send:
time.sleep(min(next_send - now, 0.002))
continue
# The jitter varies each *packet's* own spacing rather than offsetting its start, because
# the stream's timestamps have to stay strictly increasing -- a jittered t0 can overlap the
# packet before it, and the buffer, the trigger and every binary search here assume a
# monotonic clock. The mean spacing is still `dt`, so the declared rate stays honest; what
# moves is the *local* spacing, which is what a uniform grid over the window cannot model.
pdt = dt
if args.clock_jitter > 0.0:
pdt = dt * (1.0 + random.uniform(-args.clock_jitter, args.clock_jitter))
spike = 0.0
if (
args.time_glitch_at >= 0.0
and not glitched
and t_stream >= args.time_glitch_at
):
spike = args.time_glitch_by
glitched = True
print(
"mock udpstreamer: time-signal glitch at t=%.3f, +%.3f s for one packet"
% (t_stream, spike),
flush=True,
)
pkt = build_data(
counter,
t_stream,
pdt,
args.batch,
args.freq,
time_mode,
args.noise,
spike,
args.glitch_at,
args.glitch_width,
args.quiet_at,
)
burst = max(1, args.drop_burst)
if args.drop_every > 0 and drop_left == 0 and counter % args.drop_every == 0:
drop_left = burst
if drop_left > 0:
drop_left -= 1
dropped += 1
if not noted_drop:
noted_drop = True
print(
"mock udpstreamer: dropping packet %d and the %d after it"
% (counter, burst - 1),
flush=True,
)
elif (
args.reorder_every > 0
and held is None
and counter % args.reorder_every == 0
):
held = (counter, pkt, now + args.reorder_delay_ms / 1000.0)
else:
sock.sendto(pkt, peer)
if held is not None and now >= held[2]:
# Within the receiver's reorder window, this packet is put back in order and
# costs nothing. Past the window, the receiver has already committed a hole
# and this packet is what fills it.
sock.sendto(held[1], peer)
inverted += 1
if not noted_reorder:
noted_reorder = True
print(
"mock udpstreamer: sent packet %d before %d, releasing it %.1f ms late"
% (counter, held[0], args.reorder_delay_ms),
flush=True,
)
held = None
# The counter and the stream clock advance whatever became of the datagram. That
# is what makes a withheld packet a *lost* one and not a slower producer: nothing
# in a payload says which packet it is, only the header's counter does.
counter += 1
t_stream += args.batch * pdt
next_send += period
if (
args.duration > 0.0
and started is not None
and now - started > args.duration
):
print(
"mock udpstreamer: done (%d packets, %d dropped, %d inverted)"
% (counter, dropped, inverted),
flush=True,
)
return
if __name__ == "__main__":
main()
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