Python Socket编程报错10061或服务器无法接收数据问题排查

1. 服务端逻辑缺陷 #

• s.accept()仅在程序启动时执行1次，只能接受1次客户端连接。但客户端每次循环都会新建独立的Socket连接请求，第二次及以后的连接请求服务端根本不会处理，直接被系统拒绝
• 服务端绑定localhost时，仅监听127.0.0.1回环地址，使用本机实际IP访问时，请求无法被监听到，自然会返回连接拒绝错误

2. 客户端逻辑缺陷 #

• 计时逻辑完全错位：a = datetime.datetime.now()写在sendall()执行之后，统计的根本不是实际发送耗时
• 文件只读了一次：file_to_send.read(1024)第一次读完后文件指针已经到末尾，第二次及以后循环读取到的是空数据
• 每次循环新建的Socket没有主动关闭，TCP连接处于TIME_WAIT状态时端口占用会导致后续连接失败

第一步：修改服务端逻辑 #

1. 将accept()放到循环内部，每次处理完一次连接就关闭，等待下一次新的连接
2. 绑定地址改为0.0.0.0，允许所有IP地址访问，这样不管是localhost还是本机实际IP都能正常连接
   修改后的完整服务端代码：

import socket
import time
import datetime
import filecmp

HOST = '0.0.0.0'
PORT = 9100

n = 1
x = 0
average_list = []
file_comparison = "send.txt"

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)

print('I am ready for any client side request \n')

while n <= 100:
  conn, addr = s.accept()
  data = conn.recv(1024)
  file = 'receive1.txt'
  print('I am starting receiving file', file,'for the',n,'th time')
  a = datetime.datetime.now()
  f = open(file, 'wb')
  f.write(data)
  f.close()
  print('I am finishing receiving file', file,'for the',n,'th time')
  b = datetime.datetime.now()
  millidelta = (b - a).total_seconds() * 1000
  average_list.append(millidelta)
  real_average = sum(average_list) / n
  print('The time used in milliseconds to receive',file,'for the',n,'th time','is:',millidelta,'milliseconds')
  print('The average time to receive',file,'in milliseconds is:',real_average)
  if filecmp.cmp(file,file_comparison,shallow=False):
    x = x+1
  conn.close()
  n=n + 1

s.close()
print('I am done \n')
print('Total errors: ',x,'out of',n-1 )

第二步：修改客户端逻辑 #

1. 每次循环读取文件前将指针重置到文件开头，避免读取空内容
2. 调整计时逻辑，将开始计时放在sendall()之前
3. 每次发送完成后立刻关闭当前Socket，释放端口资源
   修改后的完整客户端代码：

import socket
import datetime
import filecmp

host = 'localhost'
port = 9100
fileName = "send.txt"
n = 1
average_list = []
file_to_send = open(fileName,'rb')

while n <= 100:
    file_to_send.seek(0)
    data = file_to_send.read(1024)
    s=socket.socket()
    print('I am connecting to server side:',host,'\n')
    s.connect((host,port))
    print('I am sending file',fileName,'for the',n,'th time')
    a = datetime.datetime.now()
    s.sendall(data)
    b = datetime.datetime.now()
    print('I am finishing sending file',fileName,'for the',n,'th time')
    millidelta = (b - a).total_seconds() * 1000
    average_list.append(millidelta)
    real_average = sum(average_list) / n
    print('The time used in milliseconds to send',fileName,'for the',n,'th time','is:',millidelta,'milliseconds')
    print('The average time to send',fileName,'in milliseconds is:',real_average)
    s.close()
    n = n + 1

file_to_send.close()
print('I am done')

额外排查步骤 #

如果修改后仍有连接拒绝问题，可按以下步骤验证：

• 检查系统防火墙是否开放了9100端口的TCP出入规则
• 执行netstat -ano | findstr "9100"命令确认端口没有被其他程序占用
• 跨机器访问时，确认服务端所在网络没有NAT或端口屏蔽限制

内容的提问来源于stack exchange，提问作者deth2macbeth