python - Python打孔发送syn，但不接收syn_ack和ack

Question

我有三台debian pc。一个是 stun 服务器，另外两个是客户端。我需要让这些客户端建立对等 tcp 连接。对于这种情况，我正在使用这个 github 项目。

这是服务器端代码：

#!/usr/bin/env python
import sys
import logging
import socket
import struct
import fcntl
import os
from util import *


logger = logging.getLogger()
clients = {}


def main(host='0.0.0.0', port=5005):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.bind((host, port))
    s.listen(1)
    s.settimeout(30)

    while True:
        try:
            conn, addr = s.accept()
        except socket.timeout:
            continue

        logger.info('connection address: %s', addr)
        data = recv_msg(conn)
        priv_addr = msg_to_addr(data)
        send_msg(conn, addr_to_msg(addr))
        data = recv_msg(conn)
        data_addr = msg_to_addr(data)
        if data_addr == addr:
            logger.info('client reply matches')
            clients[addr] = Client(conn, addr, priv_addr)
        else:
            logger.info('client reply did not match')
            conn.close()

        logger.info('server - received data: %s', data)

        if len(clients) == 2:
            (addr1, c1), (addr2, c2) = clients.items()
            logger.info('server - send client info to: %s', c1.pub)
            send_msg(c1.conn, c2.peer_msg())
            logger.info('server - send client info to: %s', c2.pub)
            send_msg(c2.conn, c1.peer_msg())
            clients.pop(addr1)
            clients.pop(addr2)

    conn.close()


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(message)s')
    main(*addr_from_args(sys.argv))

在其目录中有此 util.py ：

import struct
from collections import namedtuple

def addr_from_args(args, host='127.0.0.1', port=9999):
    if len(args) >= 3:
        host, port = args[1], int(args[2])
    elif len(args) == 2:
        host, port = host, int(args[1])
    else:
        host, port = host, port
    return host, port


def msg_to_addr(data):
    ip, port = data.decode('utf-8').strip().split(':')
    return (ip, int(port))


def addr_to_msg(addr):
    return '{}:{}'.format(addr[0], str(addr[1])).encode('utf-8')


def send_msg(sock, msg):
    # Prefix each message with a 4-byte length (network byte order)
    msg = struct.pack('>I', len(msg)) + msg
    sock.sendall(msg)


def recvall(sock, n):
    # Helper function to recv n bytes or return None if EOF is hit
    data = b''
    while len(data) < n:
        packet = sock.recv(n - len(data))
        if not packet:
            return None
        data += packet
    return data


def recv_msg(sock):
    # Read message length and unpack it into an integer
    raw_msglen = recvall(sock, 4)
    if not raw_msglen:
        return None
    msglen = struct.unpack('>I', raw_msglen)[0]
    # Read the message data
    return recvall(sock, msglen)


class Client(namedtuple('Client', 'conn, pub, priv')):

    def peer_msg(self):
        return addr_to_msg(self.pub) + b'|' + addr_to_msg(self.priv)

这是客户端的代码，具有相同的 util.py 但不同的 ip，服务器端的 ip 是服务器的本地 ip，客户端是服务器的公共 ip：

#!/usr/bin/env python
import sys
import logging
import socket
import struct
from threading import Event, Thread
from util import *


logger = logging.getLogger('client')
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(message)s')
STOP = Event()


def accept(port):
    logger.info("accept %s", port)
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
    s.bind(('', port))
    s.listen(1)
    s.settimeout(5)
    while not STOP.is_set():
        try:
            conn, addr = s.accept()
        except socket.timeout:
            continue
        else:
            logger.info("Accept %s connected!", port)
            # STOP.set()


def connect(local_addr, addr):
    logger.info("connect from %s to %s", local_addr, addr)
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
    s.bind(local_addr)
    while not STOP.is_set():
        try:
            s.connect(addr)
        except socket.error:
            continue
        # except Exception as exc:
        #     logger.exception("unexpected exception encountered")
        #     break
        else:
            logger.info("connected from %s to %s success!", local_addr, addr)
            # STOP.set()


def main(host='54.187.46.146', port=5005):
    sa = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sa.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sa.connect((host, port))
    priv_addr = sa.getsockname()

    send_msg(sa, addr_to_msg(priv_addr))
    data = recv_msg(sa)
    logger.info("client %s %s - received data: %s", priv_addr[0], priv_addr[1], data)
    pub_addr = msg_to_addr(data)
    send_msg(sa, addr_to_msg(pub_addr))

    data = recv_msg(sa)
    pubdata, privdata = data.split(b'|')
    client_pub_addr = msg_to_addr(pubdata)
    client_priv_addr = msg_to_addr(privdata)
    logger.info(
        "client public is %s and private is %s, peer public is %s private is %s",
        pub_addr, priv_addr, client_pub_addr, client_priv_addr,
    )

    threads = {
        '0_accept': Thread(target=accept, args=(priv_addr[1],)),
        '1_accept': Thread(target=accept, args=(client_pub_addr[1],)),
        '2_connect': Thread(target=connect, args=(priv_addr, client_pub_addr,)),
        '3_connect': Thread(target=connect, args=(priv_addr, client_priv_addr,)),
    }
    for name in sorted(threads.keys()):
        logger.info('start thread %s', name)
        threads[name].start()

    while threads:
        keys = list(threads.keys())
        for name in keys:
            try:
                threads[name].join(1)
            except TimeoutError:
                continue
            if not threads[name].is_alive():
                threads.pop(name)


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO, message='%(asctime)s %(message)s')
    main(*addr_from_args(sys.argv))

所以这就是问题所在：首先我运行服务器，然后运行一个客户端，3秒后我将运行另一个客户端，我总是正常的日志，如：

2020-12-07 17:00:24,020 - client 172.20.10.5 36102 - received data: b'5.17.81.184:65333'
2020-12-07 17:00:24,473 - client public is ('5.17.81.184', 65333) and private is ('172.20.10.5', 36102), peer public is ('25.9.153.68', 52059) private is ('192.168.1.3', 45248)
2020-12-07 17:00:24,473 - start thread 0_accept
2020-12-07 17:00:24,474 - accept 36102
2020-12-07 17:00:24,474 - start thread 1_accept
2020-12-07 17:00:24,475 - accept 52059
2020-12-07 17:00:24,475 - start thread 2_connect
2020-12-07 17:00:24,476 - connect from ('172.20.10.5', 36102) to ('25.9.153.68', 52059)
2020-12-07 17:00:24,476 - start thread 3_connect
2020-12-07 17:00:24,477 - connect from ('172.20.10.5', 36102) to ('192.168.1.3', 45248)

但是当采取 netstat 我会看到 syn-sent，我应该怎么做才能采取 syn-ack 并在那个 ack 之后？代码有问题吗？或者有什么我看不到的？

标签： pythonsocketstcpudphole-punching