#!/usr/bin/env python3
"""云服务器上的TCP转发守护(替代socat): 25432 -> db.fmode.cn:5432"""
import socket, threading, subprocess, sys

def pipe(a, b):
    try:
        while True:
            d = a.recv(65536)
            if not d:
                break
            b.sendall(d)
    except Exception:
        pass
    finally:
        try:
            a.close()
        except Exception:
            pass
        try:
            b.close()
        except Exception:
            pass

def handle(client):
    try:
        upstream = socket.create_connection(("db.fmode.cn", 5432), timeout=10)
    except Exception:
        client.close()
        return
    threading.Thread(target=pipe, args=(client, upstream), daemon=True).start()
    threading.Thread(target=pipe, args=(upstream, client), daemon=True).start()

def serve():
    srv = socket.socket()
    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    srv.bind(("127.0.0.1", 25432))
    srv.listen(16)
    print("forwarder up", flush=True)
    while True:
        c, _ = srv.accept()
        threading.Thread(target=handle, args=(c,), daemon=True).start()

serve()