Minecraft proxy

mc_split_proxy.py

import socket, threading, time

LISTEN_HOST, LISTEN_PORT = "127.0.0.1", 25566
TARGET_HOST, TARGET_PORT = "192.168.4.1", 25565

# minimal VarInt reader
def read_varint(data, off=0):
    num, shift, i = 0, 0, 0
    while True:
        if off + i >= len(data) or i >= 5:
            return None, 0   # need more
        b = data[off + i]
        num |= (b & 0x7F) << shift
        i += 1; shift += 7
        if (b & 0x80) == 0:
            return num, i

def extract_mc_packet(buf):
    """Return (packet_bytes, total_len) if a complete packet (VarInt length + payload) is present."""
    length, len_len = read_varint(buf, 0)
    if length is None:
        return None, 0
    total = len_len + length
    if len(buf) < total:
        return None, 0
    return buf[:total], total

def pipe_client_to_server(cs, ss):
    buf = bytearray()
    sent_handshake = False
    cs.settimeout(0.1)
    while True:
        try:
            chunk = cs.recv(65535)
            if not chunk:
                break
            buf.extend(chunk)
            # send complete packets one by one
            while True:
                pkt, used = extract_mc_packet(buf)
                if not pkt: break
                # first packet during connection is the handshake
                if not sent_handshake:
                    ss.sendall(pkt)           # send only the handshake
                    sent_handshake = True
                    del buf[:used]
                    time.sleep(0.15)          # <-- the crucial pause
                    continue
                # forward subsequent packets normally
                ss.sendall(pkt)
                del buf[:used]
        except socket.timeout:
            continue
    try:
        ss.shutdown(socket.SHUT_WR)
    except Exception:
        pass

def pipe_server_to_client(ss, cs):
    while True:
        data = ss.recv(65535)
        if not data:
            break
        cs.sendall(data)
    try:
        cs.shutdown(socket.SHUT_WR)
    except Exception:
        pass

def handle_client(csock, addr):
    with socket.create_connection((TARGET_HOST, TARGET_PORT)) as ssock:
        t1 = threading.Thread(target=pipe_client_to_server, args=(csock, ssock), daemon=True)
        t2 = threading.Thread(target=pipe_server_to_client, args=(ssock, csock), daemon=True)
        t1.start(); t2.start()
        t1.join(); t2.join()

def main():
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as ls:
        ls.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        ls.bind((LISTEN_HOST, LISTEN_PORT))
        ls.listen(64)
        print(f"Listening on {LISTEN_HOST}:{LISTEN_PORT}, forwarding to {TARGET_HOST}:{TARGET_PORT}")
        while True:
            c, a = ls.accept()
            threading.Thread(target=handle_client, args=(c, a), daemon=True).start()

if __name__ == "__main__":
    main()