另一个“对等方重置连接”错误

Question

我正在使用 socket 模块在 python 中创建一个服务器/客户端应用程序，无论出于何种原因，我的服务器一直在结束连接。奇怪的是，这在 Windows 上完美运行，但在 Linux 上却不行。我到处寻找可能的解决方案，但都没有奏效。下面是利用漏洞的代码的净化版本，但是成功率更高。通常它永远不会起作用。希望这仍然是足够的信息。谢谢！

服务器：

import logging
import socket
import threading
import time

def getData():
    HOST = "localhost"
    PORT = 5454

    while True:
        s = socket.socket( socket.AF_INET, socket.SOCK_STREAM )
        s.setsockopt( socket.SOL_SOCKET, socket.SO_REUSEADDR, 1 ) #because linux doesn't like reusing addresses by default

        s.bind( ( HOST, PORT ) )
        logging.debug( "Server listens" )
        s.listen( 5 )
        conn, addr = s.accept()
        logging.debug( "Client connects" )
        print "Connected by,", addr

        dataRequest = conn.recv( 1024 )
        logging.debug( "Server received message" )

        time.sleep( .01 ) #usually won't have to sample this fast

        data = """Here is some data that is approximately the length 
of the data that I am sending in my real server. It is a string that
doesn't contain any unordinary characters except for maybe a tab."""

        if not timeThread.isAlive(): #lets client know test is over
            data = "\t".join( [ data, "Terminate" ] )
            conn.send( data )
            s.close()
            print "Finished"
            print "Press Ctrl-C to quit"
            break
        else:
            logging.debug( "Server sends data back to client" )
            conn.send( data )

        logging.debug( "Server closes socket" )
        s.close()

def timer( t ):
    start = time.time()
    while ( time.time() - start ) < t:
        time.sleep( .4 )
        #sets flag for another thread not here

def main():
    global timeThread

    logging.basicConfig( filename="test.log", level=logging.DEBUG )

    #time script runs for
    t = 10 #usually much longer (hours)

    timeThread = threading.Thread( target=timer, args=( t, ) )
    dataThread = threading.Thread( target=getData, args=() )
    timeThread.start()
    dataThread.start()

    #just for testing so I can quit threads when sockets break
    while True:
        time.sleep( .1 )

    timeThread.join()
    dataThread.join()

if __name__ == "__main__":
    main()

客户：

import logging
import socket

def getData():
    dataList = []
    termStr = "Terminate"

    data = sendDataRequest()
    while termStr not in data:
        dataList.append( data )
        data = sendDataRequest()
    dataList.append( data[ :-len( termStr )-1 ] )

def sendDataRequest():
    HOST = "localhost"
    PORT = 5454

    s = socket.socket( socket.AF_INET, socket.SOCK_STREAM )

    while True:
        try:
            s.connect( ( HOST, PORT ) )
            break
        except socket.error:
            print "Connecting to server..."

    logging.debug( "Client sending message" )
    s.send( "Hey buddy, I need some data" ) #approximate length

    try:
        logging.debug( "Client starts reading from socket" )
        data = s.recv( 1024 )
        logging.debug( "Client done reading" )
    except socket.error, e:
        logging.debug( "Client throws error: %s", e )

    print data

    logging.debug( "Client closes socket" )
    s.close()

    return data

def main():
    logging.basicConfig( filename="test.log", level=logging.DEBUG )
    getData()

if __name__ == "__main__":
    main()

编辑：添加回溯

Traceback (most recent call last):
    File "client.py", line 39, in <moduel>
        main()
    File "client.py", line 36, in main
        getData()
    File "client.py", line 10, in getData
        data = sendDataRequest()
    File "client.py", line 28, in sendDataRequest
        data = s.recv( 1024 )
socket.error: [Errno 104] Connection reset by peer

编辑：添加调试

DEBUG:root:Server listens
DEBUG:root:Client sending message
DEBUG:root:Client connects
DEBUG:root:Client starts reading from socket
DEBUG:root:Server received message
DEBUG:root:Server sends data back to client
DEBUG:root:Server closes socket
DEBUG:root:Client done reading
DEBUG:root:Server listens
DEBUG:root:Client sending message
DEBUG:root:Client connects
DEBUG:root:Client starts reading from socket
DEBUG:root:Server received message
DEBUG:root:Server sends data back to client
DEBUG:root:Client done reading
DEBUG:root:Client sending message
DEBUG:root:Client starts reading from socket
DEBUG:root:Server closes socket
DEBUG:root:Client throws error: [Errno 104] Connection reset by peer
DEBUG:root:Server listens

汤姆的理论似乎是正确的。我会尝试弄清楚如何更好地关闭连接。

这没有解决，但接受的答案似乎指出了问题。

编辑：我尝试使用 Tom 的 getData() 函数，但看起来服务器仍然过早关闭连接。应该是可重复的，因为我也无法让它在 Windows 中工作。

服务器输出/回溯：

Connected by, ('127.0.0.1', 51953)
Exception in thread Thread-2:
Traceback (most recent call last):
    File "/usr/lib64/python2.6/threading.py", line 532, in __bootstrap_inner
        self.run()
    File "/usr/lib64/python2.6/threading.py", line 484, in run
        self.__target(*self.__args, **self.__kwargs)
    File "server.py", line 15, in getData
        s.bind( ( HOST, PORT ) )
    File "<string>", line 1, in bind
error: [Errno 22] Invalid argument

客户端输出/回溯：

Here is some data that is approximately the length
of the data that I am sending in my real server. It is a string that
doesn't contain any unordinary characters except for maybe a tab.
Traceback (most recent call last):
    File "client.py", line 49, in <moduel>
        main()
    File "client.py", line 46, in main
        getData()
    File "client.py", line 11, in getData
        data = sendDataRequest()
    File "client.py", line 37, in sendDataRequest
        print data
UnboundLocalError: local variable 'data' referenced before assignment

日志：

DEBUG:root:Server listens
DEBUG:root:Client sending message
DEBUG:root:Client connects
DEBUG:root:Client starts reading from socket
DEBUG:root:Server received message
DEBUG:root:Server sends data back to client
DEBUG:root:Server closes connection
DEBUG:root:Client done reading
DEBUG:root:Client closes socket
DEBUG:root:Client sending message
DEBUG:root:Client starts reading from socket
DEBUG:root:Client throws error: [Errno 104] Connection reset by peer

更新：我使用了 Tom 的 getData() 函数，但将 s.bind() 移动到循环之前并让它工作。老实说，我不知道为什么会这样，所以如果有人能解释为什么服务器关闭它的客户端套接字是安全的，但当它关闭它的服务器套接字时却不是这样，那就太酷了。谢谢！

Answer 1

虽然我无法重现此问题（在 Windows 7 64 位 Python 2.7 上），但我最好的猜测是发生了以下情况：

• 服务器监听
• 客户端连接
• 客户端发送“嘿，伙计，我需要一些数据”
• 服务器接收到这个
• 服务器将数据发送回客户端
• 服务器关闭套接字
• 客户端尝试读取socket，发现已关闭
• 客户端抛出“对等连接重置”错误。

您从客户端添加的堆栈跟踪似乎支持这一理论。是否有可能通过一些额外的日志记录或类似来证明情况并非如此？

其他注意事项： 如果您的客户端在它接收到的第一个数据中没有找到终止字符串，它会打开一个到服务器的新套接字。这在我看来是错误的 - 你应该从同一个套接字读取数据，直到你拥有所有数据。

编辑：结合更多的东西：

在您的示例日志输出中，您尚未更新代码，因此我看不到每个日志行的来源。但是，看起来您有 2 个并行运行的客户端（可能在不同的进程或线程中？），这会导致：

我刚刚注意到最后一件事。在https://docs.python.org/2/library/socket.html#example 的示例中，服务器不会关闭套接字，它会关闭通过侦听套接字生成的连接。可能是您有 2 个客户端连接到同一个服务器套接字实例，当您关闭服务器套接字时，您实际上断开了两个连接的客户端，而不仅仅是第一个。如果您正在运行多个客户端，则记录某种身份，例如。 DEBUG:root:Client(6) done reading 可能有助于证明这一点。

对于服务器的数据线程主循环，您能否尝试以下操作，将显示问题是否与关闭侦听套接字而不是连接的套接字有关：

def getData():
    HOST = "localhost"
    PORT = 5454

    s = socket.socket( socket.AF_INET, socket.SOCK_STREAM )
    # s.setsockopt( socket.SOL_SOCKET, socket.SO_REUSEADDR, 1 ) #because linux doesn't like reusing addresses by default
    s.bind( ( HOST, PORT ) )
    logging.debug( "Server listens" )
    s.listen( 5 )

    while True:

        conn, addr = s.accept()
        logging.debug( "Client connects" )
        print "Connected by,", addr

        dataRequest = conn.recv( 1024 )
        logging.debug( "Server received message" )

        time.sleep( .01 ) #usually won't have to sample this fast

        data = """Here is some data that is approximately the length 
of the data that I am sending in my real server. It is a string that
doesn't contain any unordinary characters except for maybe a tab."""

        if not timeThread.isAlive(): #lets client know test is over
            data = "\t".join( [ data, "Terminate" ] )
            conn.send( data )
            conn.close()
            print "Finished"
            print "Press Ctrl-C to quit"
            break
        else:
            logging.debug( "Server sends data back to client" )
            conn.send( data )

        logging.debug( "Server closes connection" )
        conn.close()

Answer 2

我在这里超出了我的深度，但正在调查一个可能相关的问题（Linux 上的间歇性“对等连接重置”错误，在 Windows 上工作正常），我遇到了http://scie.nti.st/2008/3/14/amazon-s3-and-connection-reset-by-peer/。我们那里有用的调试器 Garry Dolley 总结（在 2008 年！）：

“Linux 内核 2.6.17+ 增加了 TCP 窗口/缓冲区的最大大小，如果它不能处理足够大的 TCP 窗口，这会导致其他设备出现故障。设备会重置连接，我们将其视为“对等方重置连接”消息。”

他给出了一个涉及 /etc/sysctl.conf 的解决方案。我还没有尝试过，但可能值得一看？

Answer 3

我遇到了类似的问题，我在发送端被对等方重置连接。原来它发生是因为在接收方的某个地方抛出了异常。因此，当脚本意外结束时，操作系统只会对该套接字上的连接进行 RST。这是一个相当古老的线程，但对于遇到类似线程问题的任何人，我的建议是：在尝试使其复杂之前确保它是单线程的。