TCP 服务端程序退出后，为什么端口还是一直被占用？
服务端
import osimport socket
import sys
import time
import threading
from loguru import logger
from concurrent.futures import ThreadPoolExecutor
from concurrent.futures._base import Future
import multiprocessing
default_encoding: str = 'utf-8'
pool = ThreadPoolExecutor(
max_workers=20,
thread_name_prefix='simple-work-thread-pool'
)
def init_serversocket() -> socket.socket:
serversocket = socket.socket(
family=socket.AF_INET,
type=socket.SOCK_STREAM
)
# 获取本地主机名
host = socket.gethostname()
logger.debug(f'host {host}')
port = 6001
# 绑定端口号
serversocket.bind(('0.0.0.0', port))
# 设置最大连接数，超过后排队
serversocket.listen(2048)
return serversocket
def send_response(clientsocket: socket.socket, addr: tuple, response_body: bytes) -> int:
send_len: int = clientsocket.send(response_body)
clientsocket.close()
return send_len
def start_request(clientsocket: socket.socket, addr: tuple) -> int:
try:
pid = os.getpid()
# logger.debug(f'pid: {pid}, get message from {addr}')
request_body: bytes = clientsocket.recv(2048)
request_text: str = request_body.decode(encoding=default_encoding)
response_text: str = f'server get message: {request_text}'
response_body: bytes = response_text.encode(default_encoding)
# time.sleep(1)
send_len = send_response(
clientsocket=clientsocket, addr=addr, response_body=response_body)
# logger.debug(f'发送了响应')
return send_len
except Exception as error:
logger.exception(error)
def start_request_callback(future: Future) -> None:
send_len: int = future.result()
logger.debug(
f'{threading.current_thread().name}, send payload len is {send_len}')
if __name__ == "__main__":
serversocket = init_serversocket()
pool = multiprocessing.Pool(processes=16)
try:
while True:
clientsocket, addr = serversocket.accept()
clientsocket: socket.socket
addr: tuple
# future: Future = pool.submit(start_request, clientsocket, addr)
# future.add_done_callback(start_request_callback)
pool.apply_async(start_request, (clientsocket, addr))
finally:
pool.close()
pool.join()
serversocket.close()
客户端：
from base64 import encodeimport socket # 客户端 发送一个数据，再接收一个数据
import json
from loguru import logger
from concurrent.futures import ThreadPoolExecutor
import time
import multiprocessing
failture_requests = []
def send_request(index: int):
try:
# 声明socket类型，同时生成链接对象
clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
clientsocket.connect(('127.0.0.1', 6001)) # 建立一个链接，连接到本地的6969端口
payload = b'ponponon'
clientsocket.send(payload)
data = clientsocket.recv(1024)
payload = data.decode()
logger.debug(index)
clientsocket.close()
logger.debug('请求完成')
except Exception as error:
failture_requests.append(index)
logger.exception(error)
if __name__ == "__main__":
pool = multiprocessing.Pool(processes=32)
for index in range(1000000):
pool.apply_async(send_request, (index, ))
pool.close()
pool.join()
问题症状：
- 启动服务端后立刻关闭，再启动服务端也一切正常
- 启动服务端后，也启动客户端请求服务端，然后立刻关闭服务端。这个时候，启动就无法再次启动服务端，服务端会报错：
OSError: [Errno 98] Address already in use - 重点是，使用
sudo lsof -i :6001空空如也，没有任何进程再占用这个 6001 端口 - 这个
OSError: [Errno 98] Address already in use会在等待几分钟甚至几十分钟后自己消失，这个时候就能重新启动服务端了
为什么？
服务端的报错
╰─➤ python 002_socket_tcp_server_process.py 1 ↵2023-05-04 23:00:42.862 | DEBUG | __main__:init_serversocket:28 - host amd5700g
Traceback (most recent call last):
File "/home/pon/Desktop/code/me/http_wsgi_asgi_tutorial/002_socket_tcp_server_process.py", line 73, in <module>
serversocket = init_serversocket()
^^^^^^^^^^^^^^^^^^^
File "/home/pon/Desktop/code/me/http_wsgi_asgi_tutorial/002_socket_tcp_server_process.py", line 33, in init_serversocket
serversocket.bind(('0.0.0.0', port))
OSError: [Errno 98] Address already in use
sudo lsof -i :6001 的输出, 空空如也
(http_wsgi_asgi_tutorial) ╭─pon@amd5700g ~/Desktop/code/me/http_wsgi_asgi_tutorial ‹master*› ╰─➤ sudo lsof -i :6001 1 ↵
(http_wsgi_asgi_tutorial) ╭─pon@amd5700g ~/Desktop/code/me/http_wsgi_asgi_tutorial ‹master*›
为什么？为什么？是 lsof 命令不准确吗?
换成 sudo netstat -anp | grep 6001 命令试了试，有输出
╰─➤ sudo netstat -anp | grep 6001 130 ↵tcp 0 0 127.0.0.1:6001 127.0.0.1:56470 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:38966 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:50820 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:60648 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:50472 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:50860 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:50040 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:44920 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:38078 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:54364 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:35426 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:54430 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:56028 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:58210 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:38254 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:45726 TIME_WAIT -
tcp 0 0 127.0.0.1:6001 127.0.0.1:38046 TIME_WAIT -
.... 后面的省略，实在是太多了
回答：
这就是典型的 TIME_WAIT 端口占用的问题呗：程序意外退出，一个已连接的 Socket 没被主动释放，只能等操作系统最后回收。
解法即是侦听前加 SO_REUSEADDR 参数。
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # 在 bind 之前加
P.S.1. Linux 3.9 之后的内核又新增了一个 SO_REUSEPORT 参数，比 SO_REUSEADDR 来说更精细化了。不过一般来说的话都是同时设置两者的。Windows 上出于安全考虑一般还需要额外设置 SO_EXCLUSIVEADDRUSE。
P.S.2 lsof 扫的是进程，它实质看的是“某个文件被某个进程占用的情况”（Linux 下万物皆文件嘛，Socket 也是个文件）。你这进程都没了，连 pid 都没有当然就看不到了。
以上是 TCP 服务端程序退出后，为什么端口还是一直被占用？ 的全部内容， 来源链接： utcz.com/p/938871.html
