From fa05a5f8238e9e1417235711656e5062ccc843a7 Mon Sep 17 00:00:00 2001
From: "info@mode42.com" <info@mode42.com>
Date: Fri, 7 Aug 2026 18:23:28 +0000
Subject: Initial push

---
 stacks/crdop/lib/m25_host_protocol.py | 142 ++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 stacks/crdop/lib/m25_host_protocol.py

(limited to 'stacks/crdop/lib/m25_host_protocol.py')

diff --git a/stacks/crdop/lib/m25_host_protocol.py b/stacks/crdop/lib/m25_host_protocol.py
new file mode 100644
index 0000000..9212336
--- /dev/null
+++ b/stacks/crdop/lib/m25_host_protocol.py
@@ -0,0 +1,142 @@
+"""
+MAX25 native host protocol for SoftModem / audio-dummy (design freeze).
+
+Payload on data channel = AX.25 UI body **without** HDLC/FCS (same as KISS DATA).
+Control channel = line-oriented ASCII commands (M25-family, not ARDOP FEC/ARQ).
+"""
+from __future__ import annotations
+
+import socket
+import threading
+from typing import Callable, Optional
+
+# KISS-compatible data semantics; control is text lines ending in \\n
+DEFAULT_CTRL_PORT = 8515
+DEFAULT_DATA_PORT = 8516
+
+CmdFn = Callable[[str], str]
+DataRxFn = Callable[[bytes], None]
+
+
+class M25SoftModemHost:
+    """Minimal TCP host for bench / audio-dummy (ctrl + data ports)."""
+
+    def __init__(
+        self,
+        ctrl_port: int = DEFAULT_CTRL_PORT,
+        data_port: int = DEFAULT_DATA_PORT,
+        on_data_tx: Optional[Callable[[bytes], str]] = None,
+    ) -> None:
+        self.ctrl_port = ctrl_port
+        self.data_port = data_port
+        self._on_data_tx = on_data_tx or (lambda _b: "OK")
+        self._stop = threading.Event()
+        self._ctrl_srv: Optional[socket.socket] = None
+        self._data_srv: Optional[socket.socket] = None
+        self._threads: list[threading.Thread] = []
+        self._mycall = "NOCALL-0"
+        self._listen = True
+
+    def start(self) -> None:
+        self._ctrl_srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._ctrl_srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self._ctrl_srv.bind(("127.0.0.1", self.ctrl_port))
+        self._ctrl_srv.listen(4)
+        self._data_srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._data_srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self._data_srv.bind(("127.0.0.1", self.data_port))
+        self._data_srv.listen(4)
+        self._stop.clear()
+        for target, name in ((self._accept_ctrl, "ctrl"), (self._accept_data, "data")):
+            t = threading.Thread(target=target, name=f"m25-host-{name}", daemon=True)
+            t.start()
+            self._threads.append(t)
+
+    def stop(self) -> None:
+        self._stop.set()
+        for srv in (self._ctrl_srv, self._data_srv):
+            if srv is not None:
+                try:
+                    srv.close()
+                except OSError:
+                    pass
+        self._ctrl_srv = None
+        self._data_srv = None
+
+    def _accept_ctrl(self) -> None:
+        assert self._ctrl_srv is not None
+        while not self._stop.is_set():
+            try:
+                self._ctrl_srv.settimeout(0.5)
+                conn, _ = self._ctrl_srv.accept()
+            except (OSError, socket.timeout):
+                continue
+            threading.Thread(
+                target=self._ctrl_session,
+                args=(conn,),
+                daemon=True,
+            ).start()
+
+    def _ctrl_session(self, conn: socket.socket) -> None:
+        buf = b""
+        try:
+            conn.settimeout(0.5)
+            while not self._stop.is_set():
+                try:
+                    chunk = conn.recv(4096)
+                except socket.timeout:
+                    continue
+                if not chunk:
+                    break
+                buf += chunk
+                while b"\n" in buf:
+                    raw, buf = buf.split(b"\n", 1)
+                    line = raw.decode("ascii", errors="replace").strip()
+                    if not line:
+                        continue
+                    reply = self._handle_cmd(line)
+                    conn.sendall((reply + "\n").encode("ascii"))
+        finally:
+            conn.close()
+
+    def _handle_cmd(self, line: str) -> str:
+        parts = line.split()
+        cmd = parts[0].upper() if parts else ""
+        if cmd == "INITIALIZE":
+            return "OK"
+        if cmd == "PROTOCOLMODE" and len(parts) > 1 and parts[1].upper() == "KISS":
+            return "OK"
+        if cmd == "MYCALL" and len(parts) > 1:
+            self._mycall = parts[1].upper()
+            return "OK"
+        if cmd == "LISTEN":
+            self._listen = len(parts) < 2 or parts[1].upper() in ("TRUE", "1", "ON", "YES")
+            return "OK"
+        if cmd == "PING":
+            return "OK"
+        if cmd == "STATUS":
+            return f"STATUS ready mycall={self._mycall}"
+        return "ERR unknown command"
+
+    def _accept_data(self) -> None:
+        assert self._data_srv is not None
+        while not self._stop.is_set():
+            try:
+                self._data_srv.settimeout(0.5)
+                conn, _ = self._data_srv.accept()
+            except (OSError, socket.timeout):
+                continue
+            threading.Thread(
+                target=self._data_session,
+                args=(conn,),
+                daemon=True,
+            ).start()
+
+    def _data_session(self, conn: socket.socket) -> None:
+        try:
+            payload = conn.recv(4096)
+            if payload:
+                reply = self._on_data_tx(payload)
+                conn.sendall(reply.encode("ascii", errors="replace"))
+        finally:
+            conn.close()
-- 
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