DASP: drop the P-ION resend overrides, use standard 512-byte packets

The save and file-open requests used their own fixed resend intervals
(5 s / 15 s) and the hello asked for 256-byte packets. Ontrol's Sedona
Java stack does neither and works with the P-ION: the standard backoff
(1, 2, 4, 8 s) sends a busy device a few copies with the same seqNum,
which its receive window drops. Both are removed.

Also fixes a race in SendWindow.send(): the packet entered the window
before its payload and sent_time were set, so housekeeping could resend
it with an empty payload, and the device would then drop the real one
as a duplicate.

Tested on a P-ION at 192.168.1.252, App > Get with File: save 3.2 s
(2 resends), app.sab + kits.scode in 11.3 s with 500-byte chunks
(was 14.6 s at 256), device stayed up, files identical to a 256-byte
backup.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app_backup.py

@@ -23,7 +23,6 @@ import zipfile
 
 import app_state
 import sab_app
-import sox
 from ox_widget_properties import IMAGE_EXTENSIONS, ORION_KIT, RION_KIT
 
 APP_SAB = "app.sab"
@@ -163,14 +162,12 @@ def _source_entry(media, source_path):
 def save_app(client):
     """Invokes App.save on the device and waits for it to finish.
 
-    Ontrol's Niagara driver does this before every app.sab get, resending the request
+    Ontrol's Niagara driver does this before every app.sab get.
-    only every 5 s: a P-ION saving a large app takes seconds, and 1 s resends of the
-    request while it is busy are what knocked it over.
     """
     comp = client.cache_get(0) or client.load(0)
     slots = client.slot_registry.get((comp.kit_id, comp.type_id)) or []
     slot = next((s for s in slots if s["name"] == "save" and s.get("is_action")), None)
-    client.invoke(0, slot["id"] if slot else 0, send_retry=sox.SAVE_SEND_RETRY)
+    client.invoke(0, slot["id"] if slot else 0)
 
 
 class BackupResult:

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.144"
+VERSION = "0.0.0.145"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True

dasp.py

@@ -456,7 +456,7 @@ def _to_ack_more(seq_more, max_bytes):
 
 class _Packet:
     __slots__ = ("seq_num", "payload", "acked", "enqueued_time",
-                 "sent_time", "send_attempts", "send_retry", "next")
+                 "sent_time", "send_attempts", "next")
 
     def __init__(self):
         self.seq_num = 0
@@ -465,7 +465,6 @@ class _Packet:
         self.enqueued_time = 0.0
         self.sent_time = 0.0
         self.send_attempts = 1
-        self.send_retry = None      # seconds; None = the window's own interval
         self.next = None
 
 
@@ -507,17 +506,17 @@ class SendWindow:
             self._tail = None
             self._cond.notify_all()
 
-    def send(self, payload, send_retry=None):
+    def send(self, payload):
         p = _Packet()
-        p.send_retry = send_retry
         p.enqueued_time = _ticks()
+        p.payload = payload
         with self._cond:
             p.seq_num = self._seq_num & 0xFFFF
             self._seq_num = (self._seq_num + 1) & 0xFFFF
 
+        # sent_time is stamped inside the lock: send_retries() must not see the
+        # packet in the window as never sent and resend it before its first send.
         self._enqueue(p)
-        p.payload = payload
-        p.sent_time = _ticks()
         self._session._send_raw(self._to_msg(p))
 
     def _enqueue(self, p):
@@ -531,6 +530,7 @@ class SendWindow:
             else:
                 self._tail.next = p
                 self._tail = p
+            p.sent_time = _ticks()
             self._size += 1
             self._cond.notify_all()
 
@@ -620,15 +620,9 @@ class SendWindow:
             p = self._head
             while p is not None:
                 if not p.acked:
-                    if p.send_retry is not None:
+                    backoff_shift = min(p.send_attempts - 1, 32)
-                        # A request the device is slow to take -- a P-ION saving its
+                    interval = min(self.send_retry * (1 << backoff_shift),
-                        # app, opening a file -- is resent at its own steady interval:
+                                   self.max_retry_backoff)
-                        # the 1 s default resends it while the device is still busy.
-                        interval = p.send_retry
-                    else:
-                        backoff_shift = min(p.send_attempts - 1, 32)
-                        interval = min(self.send_retry * (1 << backoff_shift),
-                                       self.max_retry_backoff)
                     if now - p.sent_time >= interval:
                         self._resend(p)
                     oldest = max(oldest, now - p.enqueued_time)
@@ -784,11 +778,10 @@ class DaspSession:
 
     # ── Send / Receive ──────────────────────────────────────────
 
-    def send(self, payload, send_retry=None):
+    def send(self, payload):
-        """Queues a datagram. send_retry (seconds) overrides the resend interval."""
         if self.is_closed:
             raise DaspException(f"Session closed: {self.close_cause}")
-        self.send_window.send(payload, send_retry)
+        self.send_window.send(payload)
 
     def receive(self, timeout=1.0):
         if self.is_closed:

device_session.py

@@ -10,7 +10,6 @@ import xml.etree.ElementTree as ET
 
 import app_state
 import schema
-import sox
 from sox import SoxClient, SoxComponent, TREE, CONFIG, RUNTIME, LINKS, ALL
 
 
@@ -44,8 +43,7 @@ class DeviceSession:
 
     def connect(self, host, port, user, password):
         """DASP connect → read schema → load root. Called from background thread."""
-        self.sox_client = SoxClient(host, int(port), user, password,
+        self.sox_client = SoxClient(host, int(port), user, password)
-                                    ideal_max=sox.IDEAL_MAX, abs_max=sox.ABS_MAX)
         self.sox_client.on_event = self._on_sox_event
         self.sox_client.checksum_resolver = schema.resolve_truncated_checksum
         self.sox_client.connect()

sox.py

@@ -35,18 +35,6 @@ BUF_ID    = 7
 STR_ID    = 8
 
 
-# DASP resend intervals (seconds) for requests a device can be slow to take, as Ontrol's
-# Niagara driver sets them: a P-ION saving a large app takes 2-3+ s, and a file open can
-# take 10+ s on some devices. Resent every second instead, the device is sent copies
-# while it is still busy with the first.
-SAVE_SEND_RETRY = 5.0
-FILE_OPEN_SEND_RETRY = 15.0
-
-# The DASP packet sizes Ontrol's Niagara driver asks for in its hello.
-IDEAL_MAX = 256
-ABS_MAX = 256
-
-
 class SoxException(Exception):
     pass
 
@@ -678,13 +666,13 @@ class SoxClient:
 
     # ── Invoke Action ───────────────────────────────────────────
 
-    def invoke(self, comp_id, slot_id, type_id=None, arg=None, send_retry=None):
+    def invoke(self, comp_id, slot_id, type_id=None, arg=None):
         req = _prepare_request(ord('i'))
         req.write_u2(comp_id)
         req.write_u1(slot_id)
         if arg is not None and type_id is not None:
             encode_value(req, type_id, arg)
-        res = self.request(req, send_retry)
+        res = self.request(req)
         res.check_response('I')
 
     # ── Add Component ───────────────────────────────────────────
@@ -950,7 +938,7 @@ class SoxClient:
             opened = closed = False
             try:
                 try:
-                    res = self.request(req, FILE_OPEN_SEND_RETRY)
+                    res = self.request(req)
                 except SoxException as e:
                     # A P-ION on firmware 1.32 never answers a file get -- it drops off
                     # the network for ~20 s, as a restart would -- even for a file it
@@ -1002,21 +990,17 @@ class SoxClient:
 
     # ── Networking ──────────────────────────────────────────────
 
-    def request(self, req, send_retry=None):
+    def request(self, req):
-        results = self.requests([req], send_retry)
+        results = self.requests([req])
         return results[0]
 
-    def requests(self, reqs, send_retry=None):
+    def requests(self, reqs):
-        """Sends the batch and waits for every reply.
+        """Sends the batch and waits for every reply."""
-
-        send_retry (seconds) sets the DASP resend interval of these datagrams, for a
-        request the device is known to be slow to take.
-        """
         if self.is_closed:
             raise SoxException("SoxClient closed")
 
         if len(reqs) > 255:
-            return self._chunk_requests(reqs, send_retry)
+            return self._chunk_requests(reqs)
 
         with self._lock:
             for i, req in enumerate(reqs):
@@ -1027,7 +1011,7 @@ class SoxClient:
             self._req_event.clear()
 
             for req in reqs:
-                self._session.send(req.to_bytes(), send_retry)
+                self._session.send(req.to_bytes())
 
             deadline = time.monotonic() + 30.0
             while True:
@@ -1051,11 +1035,11 @@ class SoxClient:
             self._responses = None
             raise SoxException("Request timeout")
 
-    def _chunk_requests(self, reqs, send_retry=None):
+    def _chunk_requests(self, reqs):
         results = []
         for i in range(0, len(reqs), 255):
             chunk = reqs[i:i + 255]
-            results.extend(self.requests(chunk, send_retry))
+            results.extend(self.requests(chunk))
         return results
 
     # called by receiver thread