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"""
Modular TCP/IP Servers Service — central Main + Secondary routing for MAX25.
Public name in docs: "modular TCP/IP Servers Service".
Main instance accepts M25/1 clients and forwards sessions to Secondary max25d peers.
"""
from __future__ import annotations
import configparser
import selectors
import socket
import threading
from dataclasses import dataclass, field
from typing import Callable, Optional
LogFn = Callable[[str], None]
@dataclass
class SecondaryEndpoint:
name: str
host: str
port: int
@dataclass
class ModularTcpConfig:
enabled: bool = False
role: str = "standalone" # standalone | main | secondary
service_name: str = "modular-tcp-server"
instance_id: str = ""
secondaries: list[SecondaryEndpoint] = field(default_factory=list)
connect_timeout: float = 5.0
buffer_size: int = 65536
def load_modular_tcp(cp: configparser.ConfigParser) -> ModularTcpConfig:
cfg = ModularTcpConfig()
if not cp.has_section("modular_tcp"):
return cfg
sec = cp["modular_tcp"]
cfg.enabled = sec.get("enabled", "no").strip().lower() in ("1", "yes", "true", "on")
cfg.role = sec.get("role", cfg.role).strip().lower() or cfg.role
cfg.service_name = sec.get("service_name", cfg.service_name).strip() or cfg.service_name
cfg.instance_id = sec.get("instance_id", cfg.instance_id).strip()
if cp.has_option("modular_tcp", "connect_timeout"):
try:
cfg.connect_timeout = float(cp.get("modular_tcp", "connect_timeout"))
except (TypeError, ValueError):
cfg.connect_timeout = 5.0
if cfg.connect_timeout <= 0.0:
cfg.connect_timeout = 5.0
if cp.has_section("modular_tcp.secondaries"):
for key in cp.options("modular_tcp.secondaries"):
raw = cp.get("modular_tcp.secondaries", key).strip()
if not raw:
continue
host, _, port_s = raw.partition(":")
host = host.strip()
if not host:
continue
try:
port = int(port_s or "7326")
except (TypeError, ValueError):
port = 7326
if port < 1 or port > 65535:
port = 7326
cfg.secondaries.append(SecondaryEndpoint(name=key.strip(), host=host, port=port))
if cfg.enabled and cfg.role == "main" and not cfg.secondaries:
# Legacy comma list: secondaries = host:port,host:port
raw = sec.get("secondaries", "").strip()
if raw:
for idx, item in enumerate(x.strip() for x in raw.split(",") if x.strip()):
host, _, port_s = item.partition(":")
host = host.strip()
if not host:
continue
try:
port = int(port_s or "7326")
except (TypeError, ValueError):
port = 7326
if port < 1 or port > 65535:
port = 7326
cfg.secondaries.append(
SecondaryEndpoint(
name=f"secondary-{idx + 1}",
host=host,
port=port,
)
)
return cfg
class ModularTcpMainService:
"""Bidirectional relay: operator client <-> Secondary max25d M25/1."""
def __init__(
self,
cfg: ModularTcpConfig,
listen_host: str,
listen_port: int,
log: LogFn,
) -> None:
self.cfg = cfg
self.listen_host = listen_host
self.listen_port = listen_port
self.log = log
self._stop = threading.Event()
self._thread: Optional[threading.Thread] = None
self._rr_index = 0
self._lock = threading.Lock()
def _pick_secondary(self) -> Optional[SecondaryEndpoint]:
with self._lock:
if not self.cfg.secondaries:
return None
ep = self.cfg.secondaries[self._rr_index % len(self.cfg.secondaries)]
self._rr_index += 1
return ep
def _relay(self, client: socket.socket, upstream: socket.socket) -> None:
sel = selectors.DefaultSelector()
sel.register(client, selectors.EVENT_READ)
sel.register(upstream, selectors.EVENT_READ)
try:
while not self._stop.is_set():
for key, _ in sel.select(timeout=0.5):
sock = key.fileobj
assert isinstance(sock, socket.socket)
try:
data = sock.recv(self.cfg.buffer_size)
except OSError:
return
if not data:
return
target = upstream if sock is client else client
try:
target.sendall(data)
except OSError:
return
finally:
sel.close()
def _handle_client(self, client: socket.socket, addr: tuple[str, int]) -> None:
ep = self._pick_secondary()
if ep is None:
self.log(f"modular_tcp: no secondaries configured — drop {addr}")
client.close()
return
upstream = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
upstream.settimeout(self.cfg.connect_timeout)
try:
upstream.connect((ep.host, ep.port))
except OSError as exc:
self.log(f"modular_tcp: upstream {ep.name} {ep.host}:{ep.port} failed ({exc})")
client.close()
return
upstream.settimeout(None)
self.log(f"modular_tcp: {addr} -> {ep.name} {ep.host}:{ep.port}")
try:
self._relay(client, upstream)
finally:
for s in (client, upstream):
try:
s.shutdown(socket.SHUT_RDWR)
except OSError:
pass
s.close()
def _serve(self) -> None:
srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
srv.bind((self.listen_host, self.listen_port))
srv.listen(64)
srv.settimeout(1.0)
self.log(
f"modular_tcp: Main service '{self.cfg.service_name}' "
f"listen {self.listen_host}:{self.listen_port} "
f"secondaries={len(self.cfg.secondaries)}"
)
try:
while not self._stop.is_set():
try:
client, addr = srv.accept()
except socket.timeout:
continue
except OSError:
break
threading.Thread(
target=self._handle_client,
args=(client, addr),
daemon=True,
).start()
finally:
srv.close()
def start(self) -> None:
if self._thread is not None:
return
self._thread = threading.Thread(target=self._serve, name="modular-tcp-main", daemon=True)
self._thread.start()
def stop(self) -> None:
self._stop.set()
if self._thread is not None:
self._thread.join(timeout=3.0)
self._thread = None
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